RESUMO
BACKGROUND: In order to find a new natural resource for pain-relief, the analgesic effects of Ilex dipyrena crude extract, fractions, and subfractions were evaluated in in-vivo mouse models with possible mechanism of action. METHODS: Analgesic effects of crude extract (100 and 200 mg/kg body weight), fractions and subfractions (75 mg/kg body weight) were screened using heat-induced (tail-immersion and hot plate test) and chemical-induced (formalin and acetic acid) nociception models in mice. The samples were also tested for the elucidation of a possible mechanism through opioidergic and GABAergic systems. RESULTS: The administration of crude extract, fractions and subfractions produced analgesic responses in acetic acid, formalin, tail immersion, and hot plate model for pain similar to those obtained with the standard. Naloxone antagonized the antinociceptive effects of the tested samples, whereas bicuculline showed partial inhibition. Considering the analgesic response, crude extract, fractions, and subfractions demonstrated promising inhibitory activity against all test models for pain, which was further supported by the possible involvement of opioidergic and GABAergic systems. CONCLUSION: The results suggest that this plant may be useful in the development of new analgesic drugs. Further research with regard to the isolation of bioactive compounds is required to verify these findings.
Assuntos
Analgésicos/farmacologia , Ilex , Dor/tratamento farmacológico , Extratos Vegetais/farmacologia , Animais , Bicuculina/administração & dosagem , Antagonistas de Receptores de GABA-A/administração & dosagem , Camundongos Endogâmicos BALB C , Modelos Animais , Naloxona/administração & dosagem , Antagonistas de Entorpecentes/administração & dosagem , Testes de Toxicidade AgudaRESUMO
OBJECTIVE: Motor cortex stimulation (MCS) is a neurosurgical technique used to treat patients with refractory neuropathic pain syndromes. MCS activates the periaqueductal gray (PAG) matter, which is one of the major centers of the descending pain inhibitory system. However, the neurochemical mechanisms in the PAG that underlie the analgesic effect of MCS have not yet been described. The main goal of this study was to investigate the neurochemical mechanisms involved in the analgesic effect induced by MCS in neuropathic pain. Specifically, we investigated the release of γ-aminobutyric acid (GABA), glycine, and glutamate in the PAG and performed pharmacological antagonism experiments to validate of our findings. METHODS: Male Wistar rats with surgically induced chronic constriction of the sciatic nerve, along with sham-operated rats and naive rats, were implanted with both unilateral transdural electrodes in the motor cortex and a microdialysis guide cannula in the PAG and subjected to MCS. The MCS was delivered in single 15-minute sessions. Neurotransmitter release was evaluated in the PAG before, during, and after MCS. Quantification of the neurotransmitters GABA, glycine, and glutamate was performed using a high-performance liquid chromatography system. The mechanical nociceptive threshold was evaluated initially, on the 14th day following the surgery, and during the MCS. In another group of neuropathic rats, once the analgesic effect after MCS was confirmed by the mechanical nociceptive test, rats were microinjected with saline or a glycine antagonist (strychnine), a GABA antagonist (bicuculline), or a combination of glycine and GABA antagonists (strychnine+bicuculline) and reevaluated for the mechanical nociceptive threshold during MCS. RESULTS: MCS reversed the hyperalgesia induced by peripheral neuropathy in the rats with chronic sciatic nerve constriction and induced a significant increase in the glycine and GABA levels in the PAG in comparison with the naive and sham-treated rats. The glutamate levels remained stable under all conditions. The antagonism of glycine, GABA, and the combination of glycine and GABA reversed the MCS-induced analgesia. CONCLUSIONS: These results suggest that the neurotransmitters glycine and GABA released in the PAG may be involved in the analgesia induced by cortical stimulation in animals with neuropathic pain. Further investigation of the mechanisms involved in MCS-induced analgesia may contribute to clinical improvements for the treatment of persistent neuropathic pain syndromes.
Assuntos
Analgesia/métodos , Estimulação Encefálica Profunda , Glicina/fisiologia , Córtex Motor/fisiopatologia , Neuralgia/terapia , Substância Cinzenta Periaquedutal/fisiopatologia , Ciática/terapia , Ácido gama-Aminobutírico/fisiologia , Animais , Bicuculina/administração & dosagem , Bicuculina/toxicidade , Vias Eferentes/efeitos dos fármacos , Vias Eferentes/fisiologia , Antagonistas GABAérgicos/administração & dosagem , Antagonistas GABAérgicos/toxicidade , Ácido Glutâmico/análise , Glicina/análise , Glicina/antagonistas & inibidores , Glicina/uso terapêutico , Hiperalgesia/tratamento farmacológico , Hiperalgesia/fisiopatologia , Hiperalgesia/terapia , Masculino , Microdiálise , Microinjeções , Neuralgia/tratamento farmacológico , Neuralgia/fisiopatologia , Limiar da Dor , Substância Cinzenta Periaquedutal/efeitos dos fármacos , Ratos , Ratos Wistar , Nervo Isquiático/lesões , Ciática/tratamento farmacológico , Ciática/fisiopatologia , Estricnina/administração & dosagem , Estricnina/toxicidade , Ácido gama-Aminobutírico/análise , Ácido gama-Aminobutírico/uso terapêuticoRESUMO
Inhibition of GABAergic neural inputs to dorsal columns of the periaqueductal grey matter (dPAG), posterior (PH) and dorsomedial (DMH) hypothalamic nuclei elicits distinct types of escape behavioural reactions. To differentiate between the variety and intensity of panic-related behaviours, the pattern of defensive behaviours evoked by blockade of GABAA receptors in the DMH, PH and dPAG were compared in a circular open-field test and in a recently designed polygonal arena. In the circular open-field, the defensive behaviours induced by microinjection of bicuculline into DMH and PH were characterised by defensive alertness behaviour and vertical jumps preceded by rearing exploratory behaviour. On the other hand, explosive escape responses interspersed with horizontal jumps and freezing were observed after the blockade of GABAA receptors on dPAG neurons. In the polygonal arena apparatus, the escape response produced by GABAergic inhibition of DMH and PH neurons was directed towards the burrow. In contrast, the blockade of GABAA receptors in dPAG evoked non-oriented escape behaviour characterised by vigorous running and horizontal jumps in the arena. Our findings support the hypothesis that the hypothalamic nuclei organise oriented escape behavioural responses whereas non-oriented escape is elaborated by dPAG neurons. Additionally, the polygonal arena with a burrow made it easy to discriminate and characterise these two different patterns of escape behavioural responses. In this sense, the polygonal arena with a burrow can be considered a good methodological tool to discriminate between these two different patterns of escape behavioural responses and is very useful as a new experimental animal model of panic attacks.
Assuntos
Reação de Fuga , Abrigo para Animais , Testes Psicológicos , Animais , Bicuculina/administração & dosagem , Desenho de Equipamento , Reação de Fuga/efeitos dos fármacos , Reação de Fuga/fisiologia , Antagonistas de Receptores de GABA-A/administração & dosagem , Hipotálamo/efeitos dos fármacos , Hipotálamo/metabolismo , Masculino , Microinjeções , Atividade Motora/efeitos dos fármacos , Atividade Motora/fisiologia , Substância Cinzenta Periaquedutal/efeitos dos fármacos , Substância Cinzenta Periaquedutal/metabolismo , Ratos Wistar , Receptores de GABA-A/efeitos dos fármacos , Receptores de GABA-A/metabolismoRESUMO
Male Syrian hamsters (Mesocricetus auratus) treated with anabolic/androgenic steroids (AAS) during adolescence (P27-P56) display highly escalated and mature forms of offensive aggression correlated with increased γ-aminobutyric acid (GABA) afferent development as well as decreased GABAA receptors in the lateroanterior hypothalamus (LAH) - an area of convergence for developmental and neuroplastic changes that underlie offensive aggressive behaviors in hamsters. This study investigated whether microinfusion of a GABAA receptor agonist (muscimol; 0.01-1.0 pmol/l) or antagonist (bicuculline; 0.04-4.0 pmol/l) directly into the LAH modulate adolescent AAS-induced offensive aggression. Activation of LAH GABAA receptors enhanced adolescent AAS-induced offensive aggression, beginning at the 0.1 pmol/l dose, when compared with AAS-treated animals injected with saline into the LAH. Importantly, GABAA receptor agonism within the LAH significantly increased the frequency of belly/rear attacks, while simultaneously decreasing the frequency of frontal attacks. These data identify a neuroanatomical locus where GABAA receptor activation functions to enhance aggression in adolescent AAS-treated animals, while also promoting the display of mature forms of aggression and suppressing juvenile play behaviors.
Assuntos
Agressão/efeitos dos fármacos , Hipotálamo/metabolismo , Receptores de GABA-A/metabolismo , Ácido gama-Aminobutírico/metabolismo , Anabolizantes/farmacologia , Androgênios/farmacologia , Animais , Comportamento Animal/efeitos dos fármacos , Bicuculina/administração & dosagem , Bicuculina/farmacologia , Cricetinae , Relação Dose-Resposta a Droga , Agonistas de Receptores de GABA-A/administração & dosagem , Agonistas de Receptores de GABA-A/farmacologia , Antagonistas de Receptores de GABA-A/administração & dosagem , Antagonistas de Receptores de GABA-A/farmacologia , Hipotálamo/efeitos dos fármacos , Masculino , Mesocricetus , Muscimol/administração & dosagem , Muscimol/farmacologia , Receptores de GABA-A/efeitos dos fármacos , Transdução de Sinais/efeitos dos fármacosRESUMO
Interaction with the gamma-aminobutyric-acid-type-A (GABAA) receptors is recognized as an important component of the mechanism of propofol, a sedative-hypnotic drug commonly used as anesthetic. However the contribution of GABAA receptors to the central nervous system suppression is still not well understood, especially in the thalamocortical network. In the present study, we investigated if intracerebral injection of bicuculline (a GABAA receptor antagonist) into the thalamus ventral posteromedial nucleus (VPM, a thalamus specific relay nuclei that innervated S1 mostly) could reverse propofol-induced cortical suppression, through recording the changes of both spontaneous and somatosensory neural activities in rat's somatosensory cortex (S1). We found that after injection of bicuculline into VPM, significant increase of neural activities were observed in all bands of local field potentials (total band, 182±6%), while the amplitude of all components in somatosensory evoked potentials were also increased (negative, 121±9% and positive, 124±6%).These data support that the potentiation of GABAA receptor-mediated synaptic inhibition in a thalamic specific relay system seems to play a crucial role in propofol-induced cortical suppression in the somatosensory cortex of rats.
Assuntos
Propofol/farmacologia , Receptores de GABA-A/metabolismo , Córtex Somatossensorial/efeitos dos fármacos , Córtex Somatossensorial/fisiologia , Tálamo/metabolismo , Vias Aferentes , Anestésicos Intravenosos/administração & dosagem , Anestésicos Intravenosos/farmacologia , Animais , Bicuculina/administração & dosagem , Bicuculina/farmacologia , Potenciais Somatossensoriais Evocados , Feminino , Antagonistas de Receptores de GABA-A/administração & dosagem , Antagonistas de Receptores de GABA-A/farmacologia , Masculino , Propofol/administração & dosagem , Ratos , Transmissão Sináptica/efeitos dos fármacos , Tálamo/efeitos dos fármacos , Núcleos Ventrais do Tálamo/efeitos dos fármacos , Núcleos Ventrais do Tálamo/metabolismoRESUMO
Centrally released oxytocin (OXT) has anxiolytic and anti-stress effects. Delayed gastric emptying (GE) induced by acute restraint stress (ARS) for 90 min is completely restored following 5 consecutive days of chronic homotypic restraint stress (CHS), via up-regulating hypothalamic OXT expression in rats. However, the mechanism behind the restoration of delayed GE following CHS remains unclear. Gamma-aminobutyric acid (GABA)-projecting neurons in the paraventricular nucleus (PVN) have been shown to inhibit corticotropin releasing factor (CRF) synthesis via GABA(A) receptors. We hypothesized that GABA(A) receptors are involved in mediating the inhibitory effect of OXT on CRF expression in the PVN, which in turn restores delayed GE following CHS. OXT (0.5 µg) and selective GABA(A) receptor antagonist, bicuculline methiodide (BMI) (100 ng), were administered intracerebroventricularly (icv). Solid GE was measured under non-stressed (NS), ARS and CHS conditions. Expression of CRF mRNA in the PVN was evaluated by real time RT-PCR. Neither OXT nor BMI changed GE and CRF mRNA expression under NS conditions. Delayed GE and increased CRF mRNA expression induced by ARS were restored by icv-injection of OXT. The effects of OXT on delayed GE and increased CRF mRNA expression in ARS were abolished by icv-injection of BMI. Following CHS, delayed GE was completely restored in saline (icv)-injected rats, whereas daily injection of BMI (icv) attenuated the restoration of delayed GE. Daily injection of BMI (icv) significantly increased CRF mRNA expression following CHS. It is suggested that central OXT inhibits ARS-induced CRF mRNA expression via GABA(A) receptors in the PVN. GABAergic system is also involved in OXT-mediated adaptation response of delayed GE under CHS conditions.
Assuntos
Hormônio Liberador da Corticotropina/biossíntese , Regulação da Expressão Gênica , Hipotálamo/metabolismo , Ocitocina/metabolismo , Receptores de GABA-A/metabolismo , Estresse Psicológico/fisiopatologia , Adaptação Fisiológica/fisiologia , Animais , Bicuculina/administração & dosagem , Bicuculina/análogos & derivados , Esvaziamento Gástrico/fisiologia , Expressão Gênica , Hipotálamo/efeitos dos fármacos , Injeções Intraventriculares , Masculino , RNA Mensageiro/análise , Ratos , Ratos Sprague-Dawley , Restrição Física , Reação em Cadeia da Polimerase Via Transcriptase ReversaRESUMO
In cerebral ischemia, transmission by the inhibitory neurotransmitter, γ-aminobutyric acid (GABA) is altered. This study was performed to determine whether blockade of GABA(A) receptor would affect regional cerebral blood flow (rCBF) and blood-brain barrier (BBB) permeability in a focal ischemic area of the brain. Rats were anesthetized with isoflurane and mechanically ventilated. Fifteen minutes after a permanent middle cerebral artery (MCA) occlusion, one half of the rats were infused with bicuculline 1mg/kg/min iv for 2 min followed by 0.1mg/kg/min iv to the end of the experiment. The other half were infused with normal saline. At one hour after MCA occlusion, rCBF was determined using ¹4C-iodoantipyrine and BBB permeability was determined by measuring the transfer coefficient (Ki) of ¹4C-α-aminoisobutyric acid. With MCA occlusion, rCBF was decreased in the ischemic cortex (IC) (-70%) in the control rats. In the bicuculline treated rats, the rCBF of the IC was lower (-48%) than the contralateral cortex but higher than the rCBF of the IC of the control rats (+55%). MCA occlusion increased Ki in the IC of the control rats (+72%) and bicuculline administration increased Ki further (+53%) in the IC. Blockade of GABA(A) receptors did not significantly affect rCBF or BBB permeability in the non-ischemic brain regions under isoflurane anesthesia. Our data demonstrated that blockade of GABA(A) receptors increased rCBF and enhanced the BBB disruption in focal cerebral ischemia. Our data suggest that GABA(A) receptors are involved, at least in part, in modulating rCBF and BBB disruption in focal cerebral ischemia.
Assuntos
Bicuculina/uso terapêutico , Barreira Hematoencefálica/efeitos dos fármacos , Isquemia Encefálica/tratamento farmacológico , Circulação Cerebrovascular/efeitos dos fármacos , Antagonistas de Receptores de GABA-A/uso terapêutico , Infarto da Artéria Cerebral Média/tratamento farmacológico , Ácidos Aminoisobutíricos , Animais , Antipirina/análogos & derivados , Bicuculina/administração & dosagem , Bicuculina/farmacocinética , Bicuculina/farmacologia , Isquemia Encefálica/etiologia , Isquemia Encefálica/fisiopatologia , Radioisótopos de Carbono , Avaliação Pré-Clínica de Medicamentos , Antagonistas de Receptores de GABA-A/administração & dosagem , Antagonistas de Receptores de GABA-A/farmacocinética , Antagonistas de Receptores de GABA-A/farmacologia , Humanos , Infarto da Artéria Cerebral Média/complicações , Infarto da Artéria Cerebral Média/fisiopatologia , Infusões Intravenosas , Masculino , Ratos , Ratos Wistar , Receptores de GABA-A/fisiologia , Ácido gama-Aminobutírico/fisiologiaRESUMO
The neurobiological substrate for morphine self-administration in animals is believed to involve the dopamine system of the nucleus accumbens. Our previous study has shown that acupuncture at the acupoint Shenmen (HT7) reduced dopamine release in the nucleus accumbens and behavioral hyperactivity induced by systemic administration of morphine. Here we investigated the effect of acupuncture on morphine self-administration and potential roles of GABA receptors in the mechanisms behind acupuncture. Male Sprague-Dawley rats were trained to self-administer morphine (0.1 mg/kg per infusion) during daily 1-h session under fixed-ratio 1 schedule. Following the stable responding on morphine self-administration, acupuncture was applied to HT7 points bilaterally (1 min) prior to the testing session. Another groups of rats were given the GABA(B) receptor antagonist SCH 50911 (3.0 mg/kg, i.p.), the GABA(A) receptor antagonist bicuculline (1.0 mg/kg, i.p.) or saline 30 min prior to the acupuncture treatment. We have found that acupuncture at the acupoint HT7, but not at the control point Yangxi (LI5), significantly decreased morphine self-administration. Moreover, either SCH 50911 or bicuculline blocked the inhibitory effects of acupuncture on morphine self-administration. Taken together, the current results suggest that acupuncture at specific HT7 points regulates the reinforcing effects of morphine via regulation of GABA receptors.
Assuntos
Terapia por Acupuntura/métodos , Morfina/administração & dosagem , Entorpecentes/administração & dosagem , Receptores de GABA-A/metabolismo , Receptores de GABA-B/metabolismo , Autoadministração/métodos , Animais , Bicuculina/administração & dosagem , Bicuculina/farmacologia , Comportamento Alimentar , Antagonistas GABAérgicos/administração & dosagem , Antagonistas GABAérgicos/farmacologia , Antagonistas de Receptores de GABA-A , Antagonistas de Receptores de GABA-B , Masculino , Morfina/farmacologia , Morfolinas/administração & dosagem , Morfolinas/farmacologia , Entorpecentes/farmacologia , Ratos , Ratos Sprague-Dawley , Fatores de TempoRESUMO
We previously showed that the defense response elicited by stressors was attenuated in prepro-orexin knockout mice and in orexin neuron-ablated mice, and we proposed that orexin serves as a master switch within multiple efferent pathways that mediate the defense response. In this study we sought to determine whether excitation of the amygdala (AMG) or the bed nucleus of stria terminalis (BNST) activates orexin-containing neurons and whether those neurons are essential in eliciting cardiorespiratory responses to the stimulus. In urethane-anesthetized mice, the GABA-A receptor antagonist bicuculline was microinjected into the AMG or BNST and blood pressure, heart rate, and respiration were measured. Injection of bicuculline in either site induced long-lasting dose-dependent cardiorespiratory excitation in wild-type mice. In contrast, mice in which orexin neurons had been ablated demonstrated no such response after activation of the AMG and an attenuated response after activation of the BNST. Double immunohistochemical staining for orexin and c-Fos, an indicator of neural activation, revealed that an injection of bicuculline induced significantly larger numbers of orexin positive neurons that expressed c-Fos in the perifornical/dorsomedial hypothalamus (58.2+/-6.4% into AMG and 66.4+/-6.6% into BNST, n=3 each) than did vehicle (18.2+/-4.4% into AMG and 28.3+/-2.1% into BNST). Disinhibition to the BNST induced widespread expression of c-Fos not only in orexin-containing neurons but also other neurons in the hypothalamus. We conclude that orexin-containing neurons in the medial hypothalamus mediate at least a part of AMG- and BNST-induced cardiorespiratory responses.
Assuntos
Tonsila do Cerebelo/efeitos dos fármacos , Pressão Sanguínea/efeitos dos fármacos , Frequência Cardíaca/efeitos dos fármacos , Hipotálamo/citologia , Peptídeos e Proteínas de Sinalização Intracelular/fisiologia , Neurônios/fisiologia , Neuropeptídeos/fisiologia , Respiração/efeitos dos fármacos , Núcleos Septais/efeitos dos fármacos , Animais , Bicuculina/administração & dosagem , Bicuculina/farmacologia , Pressão Sanguínea/fisiologia , Antagonistas GABAérgicos/administração & dosagem , Antagonistas GABAérgicos/farmacologia , Frequência Cardíaca/fisiologia , Hipotálamo/efeitos dos fármacos , Imuno-Histoquímica , Peptídeos e Proteínas de Sinalização Intracelular/deficiência , Peptídeos e Proteínas de Sinalização Intracelular/genética , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Microinjeções , Neurônios/efeitos dos fármacos , Neurônios/metabolismo , Neuropeptídeos/deficiência , Neuropeptídeos/genética , Neurotransmissores/fisiologia , Orexinas , Reação em Cadeia da Polimerase , Proteínas Proto-Oncogênicas c-fos/metabolismoRESUMO
The role of GABA(A) receptors in the mediodorsal thalamus (mdT) in turning behaviour of rats was studied. Neither the GABA(A) receptor agonist muscimol (50 ng) nor the antagonist bicuculline (200 ng) unilaterally injected into the mdT elicited any behavioural change. Unilateral injection of the acetylcholine receptor agonist (carbachol, 5 microg) into the nucleus accumbens shell has been found to elicit contraversive circling while unilateral injection of a mixture of dopamine D(1) ((+/-)-1-phenyl-2,3,4,5-tetrahydro-1H-3-benzazepine-7,8-diol [SKF 38393], 5 microg) and D(2) (quinpirole, 10 microg) receptor agonists into the same site is known to elicit contraversive pivoting. The contraversive circling induced by unilateral injection of carbachol (5 microg) into the nucleus accumbens shell was dose-dependently inhibited by muscimol (25 and 50 ng) injected into the mdT. This inhibitory effect of muscimol (50 ng) was antagonised by co-administration of bicuculline (200 ng), which alone did not modify the contraversive circling induced by carbachol (5 microg). The contraversive pivoting induced by unilateral injection of a mixture of SKF 38393 (5 microg) and quinpirole (10 microg) into the nucleus accumbens shell was inhibited by muscimol (25 and 50 ng) injected into the mdT, whereas bicuculline (200 ng) injected into the mdT did not significantly modify the pivoting. The inhibitory effect of muscimol (50 ng) on the pivoting induced by a mixture of SKF 38393 (5 microg) and quinpirole (10 microg) was not dose-dependent and not antagonised by bicuculline (200 ng). The present study suggests that GABA(A) receptors in the mdT play a limited role in spontaneously occurring locomotor activity. Secondly, this study demonstrates that GABA(A) receptors in the mdT transmit accumbens-dependent cholinergic circling, but not accumbens-dependent dopaminergic pivoting, to other brain structures. Finally, the present study shows that muscimol-sensitive, non-GABA(A) receptors in the mdT influence the accumbens-dependent dopaminergic pivoting. To what extent GABA(B) receptors in the mdT mediate the muscimol-induced effects upon the dopaminergic pivoting behaviour requires additional research.
Assuntos
Acetilcolina/metabolismo , Dopamina/metabolismo , Atividade Motora/fisiologia , Receptores de GABA-A/metabolismo , Tálamo/fisiologia , 2,3,4,5-Tetra-Hidro-7,8-Di-Hidroxi-1-Fenil-1H-3-Benzazepina/administração & dosagem , Animais , Bicuculina/administração & dosagem , Carbacol/administração & dosagem , Agonistas Colinérgicos/administração & dosagem , Agonistas de Dopamina/administração & dosagem , Relação Dose-Resposta a Droga , Agonistas GABAérgicos/administração & dosagem , Antagonistas GABAérgicos/administração & dosagem , Agonistas de Receptores de GABA-A , Antagonistas de Receptores de GABA-A , Masculino , Atividade Motora/efeitos dos fármacos , Muscimol/administração & dosagem , Quimpirol/administração & dosagem , Ratos , Ratos Wistar , Tálamo/efeitos dos fármacosRESUMO
1. Several groups have reported that melatonin produces a significant decrease in blood pressure in mammals and that pinealectomy in rats causes hypertension. The purpose of the present study was to investigate the effects of melatonin and bicuculline methiodide on the blood pressure of rats, both in the developing and fully developed stage of stress-induced hypertension (SIH). 2. Rats with SIH were generated by mild electric foot shocks for 15 days, after which tail arterial systolic pressure and plasma angiotensin (Ang) II levels were measured. The effects of melatonin injections (i.p. or i.c.v.) on mean arterial pressure (MAP) in rats with SIH were also determined. 3. Pretreatment with 1 mg/kg, i.p., melatonin significantly diminished the elevated tail arterial systolic pressure and plasma AngII levels caused by 15 days stress. The suppressive effects of melatonin were blocked by i.p. injection of 1 mg/kg bicuculline methiodide, an antagonist of the GABA(A) receptor. 4. Intraperitoneal (0.2, 0.5 and 1 mg/kg) or i.c.v. (0.15 and 1.5 microg/3 microL) injection of melatonin produced a dose-dependent lowering of MAP in rats with SIH. The antihypertensive response induced by melatonin was blocked by injection of both 1 mg/kg, i.p., and 1.5 x 10(6) microg/3 microL, i.c.v., bicuculline methiodide. 5. In conclusion, melatonin not only prevents increases in blood pressure during the developing stage of SIH, but can also reduce the blood pressure of rats that have already developed SIH. The antihypertensive effect of melatonin may be mediated by GABA(A) receptors through inhibition of plasma AngII levels.
Assuntos
Pressão Sanguínea/efeitos dos fármacos , Hipertensão/tratamento farmacológico , Hipertensão/etiologia , Melatonina/farmacologia , Receptores de GABA-A/fisiologia , Estresse Psicológico/complicações , Animais , Anti-Hipertensivos/administração & dosagem , Anti-Hipertensivos/farmacologia , Anti-Hipertensivos/uso terapêutico , Bicuculina/administração & dosagem , Bicuculina/análogos & derivados , Ventrículos Cerebrais/efeitos dos fármacos , Regulação para Baixo/efeitos dos fármacos , Avaliação Pré-Clínica de Medicamentos , Frequência Cardíaca/efeitos dos fármacos , Hipertensão/fisiopatologia , Injeções Intraperitoneais , Injeções Intraventriculares , Masculino , Melatonina/administração & dosagem , Melatonina/uso terapêutico , Distribuição Aleatória , Ratos , Ratos Wistar , Receptores de GABA-A/metabolismo , Estresse Psicológico/tratamento farmacológico , Estresse Psicológico/fisiopatologiaRESUMO
Acupuncture or acupuncture-like stimulation applied to different body areas can modify autonomic nerve activity to various organs, including gut, bladder, adrenal medulla, and the heart. We studied the reflex bradycardia in response to insertion into the skin and underlying muscles and twisting of an acupuncture needle in pentobarbital-anesthetized rats. We found that acupuncture-like stimulation of forelimb, hindlimb, chest, and abdomen all produced significant heart rate decreases. Rate minima were reached at the end of the 60-second stimulation episode and significant bradycardia persisted for about 40 s after stimulation ended. Heart rate decreases were paralleled by decreases in cardiac sympathetic nerve activity, and could be produced by electrical stimulation of group IV muscle afferent fibers (tibial nerve). Electrical stimulation of the tibial nerve at rates as low as 0.1-2 Hz was effective for eliciting heart rate decreases. Nerve fiber groups were defined by stimulation of and recording from tibial nerve. Activation of groups I, II, or III fiber was ineffective for eliciting the reflex bradycardia. Sympathectomy, high spinal transection, or infusion of the GABA(A) receptor antagonist, bicuculline, into the cisterna magna were all effective for disrupting the reflex bradycardia. Vagotomy and opioid receptor blockade were ineffective for disrupting the reflex pathway. We conclude that the reflex pathway to decrease heart rate by acupuncture-like stimulation consists of mainly group IV muscle afferent fibers whose activity (even very low rate of activity) leads to the activation of GABA-ergic neurons in the brainstem and an inhibition of sympathetic outflow to the heart.
Assuntos
Vias Aferentes/fisiologia , Inibição Neural/fisiologia , Reflexo/fisiologia , Sistema Nervoso Simpático/fisiologia , Pontos de Acupuntura , Vias Aferentes/efeitos dos fármacos , Anestesia , Animais , Bicuculina/administração & dosagem , Bicuculina/farmacologia , Bradicardia/fisiopatologia , Estimulação Elétrica/métodos , Antagonistas GABAérgicos/administração & dosagem , Antagonistas GABAérgicos/farmacologia , Frequência Cardíaca/efeitos dos fármacos , Frequência Cardíaca/fisiologia , Injeções Intravenosas , Masculino , Músculo Esquelético/efeitos dos fármacos , Músculo Esquelético/inervação , Músculo Esquelético/fisiologia , Naloxona/administração & dosagem , Naloxona/farmacologia , Antagonistas de Entorpecentes/administração & dosagem , Antagonistas de Entorpecentes/farmacologia , Inibição Neural/efeitos dos fármacos , Neurônios/fisiologia , Ratos , Ratos Wistar , Reflexo/efeitos dos fármacos , Pele/inervação , Sistema Nervoso Simpático/efeitos dos fármacos , Nervo Tibial/fisiologia , Vagotomia/métodosRESUMO
The aim of the present study was intended to investigate the ameliorating effects of emodin on memory consolidation via cholinergic, serotonergic and GABAergic neuronal systems in rats. First, we evaluated the ameliorating effects of emodin on cycloheximide (CXM)-induced impairment of passive avoidance response in rats. Secondly, we clarified the role of cholinergic, serotonergic or GABAergic system on the ameliorating effect of emodin by using 5-HT1A receptor partial agonist, 5-HT2 receptor antagonist, GABAB agonist, GABAA antagonist and muscarinic receptor antagonist. Emodin protected the rat from CXM-induced memory consolidation impairment. The beneficial effect of emodin on CXM-induced memory consolidation impairment was amplified by 8-OH-DPAT (5-HT1A receptor partial agonist) and ritanserin (5-HT2 receptor antagonist), but reduced by scopolamine. These results suggested that the beneficial effect of emodin on CXM-induced memory consolidation impairment was amplified by serotonergic 5-HT1A-receptor partial agonist and 5-HT2 receptor antagonist but reduced by muscarinic receptor antagonist.
Assuntos
Emodina/farmacologia , Transtornos da Memória/prevenção & controle , Memória/efeitos dos fármacos , Polygonatum/química , 8-Hidroxi-2-(di-n-propilamino)tetralina/administração & dosagem , 8-Hidroxi-2-(di-n-propilamino)tetralina/farmacologia , Administração Oral , Animais , Baclofeno/administração & dosagem , Baclofeno/farmacologia , Bicuculina/administração & dosagem , Bicuculina/farmacologia , Cicloeximida/administração & dosagem , Cicloeximida/toxicidade , Relação Dose-Resposta a Droga , Emodina/administração & dosagem , Emodina/isolamento & purificação , Agonistas GABAérgicos/administração & dosagem , Agonistas GABAérgicos/farmacologia , Antagonistas GABAérgicos/administração & dosagem , Antagonistas GABAérgicos/farmacologia , Injeções Subcutâneas , Aprendizagem/efeitos dos fármacos , Masculino , Transtornos da Memória/induzido quimicamente , Raízes de Plantas/química , Inibidores da Síntese de Proteínas/administração & dosagem , Inibidores da Síntese de Proteínas/toxicidade , Ratos , Ratos Sprague-Dawley , Ritanserina/administração & dosagem , Ritanserina/farmacologia , Escopolamina/administração & dosagem , Escopolamina/farmacologia , Agonistas do Receptor 5-HT1 de Serotonina , Antagonistas do Receptor 5-HT2 de SerotoninaRESUMO
Studies in behaving animals suggest that neurones located in the perifornical (PF) region of the posterior hypothalamus promote wakefulness and suppress sleep. Among such cells are those that synthesize the excitatory peptides, orexins (ORX). Lack of ORX, or their receptors, is associated with narcolepsy/cataplexy, a disorder characterized by an increased pressure for rapid eye movement (REM) sleep. We used anaesthetized rats in which pontine microinjections of a cholinergic agonist, carbachol, can repeatedly elicit REM sleep-like episodes to test whether activation of PF cells induced by antagonism of endogenous, GABA(A) receptor-mediated, inhibition suppresses the ability of the brainstem to generate REM sleep-like state. Microinjections of the GABA(A) receptor antagonist, bicuculline (20 nl, 1 mm), into the PF region elicited cortical and hippocampal activation, increased the respiratory rate and hypoglossal nerve activity, induced c-fos expression in ORX and other PF neurones, and increased c-fos expression in pontine A7 and other noradrenergic neurones. The ability of pontine carbachol to elicit any cortical, hippocampal or brainstem component of the REM sleep-like response was abolished during the period of bicuculline-induced activation. The activating and REM sleep-suppressing effect of PF bicuculline was not attenuated by systemic administration of the ORX type 1 receptor antagonist, SB334867. Thus, activation of PF neurones that are endogenously inhibited by GABA(A) receptors is sufficient to turn off the brainstem REM sleep-generating network; the effect is, at least in part, due to activation of pontine noradrenergic neurones, but is not mediated by ORX type 1 receptors. A malfunction of the pathway that originates in GABA(A) receptor-expressing PF neurones may cause narcolepsy/cataplexy.
Assuntos
Carbacol/farmacologia , Hipotálamo/fisiologia , Inibição Neural/fisiologia , Neurônios/fisiologia , Norepinefrina/metabolismo , Ponte/fisiologia , Sono REM/fisiologia , Animais , Benzoxazóis/farmacologia , Bicuculina/administração & dosagem , Bicuculina/farmacologia , Carbacol/administração & dosagem , Carbacol/antagonistas & inibidores , Fórnice , Antagonistas GABAérgicos/administração & dosagem , Antagonistas GABAérgicos/farmacologia , Hipotálamo/citologia , Hipotálamo/efeitos dos fármacos , Injeções , Peptídeos e Proteínas de Sinalização Intracelular/fisiologia , Masculino , Naftiridinas , Neurônios/efeitos dos fármacos , Neurônios/metabolismo , Neuropeptídeos/fisiologia , Receptores de Orexina , Orexinas , Ponte/efeitos dos fármacos , Ratos , Ratos Sprague-Dawley , Receptores Acoplados a Proteínas G/antagonistas & inibidores , Receptores de Neuropeptídeos/antagonistas & inibidores , Sono REM/efeitos dos fármacos , Ureia/análogos & derivados , Ureia/farmacologiaRESUMO
Neurons in the region of dorsomedial hypothalamus are involved in the organization of the physiological responses to emotional stress. We have recently shown that the cardiovascular response evoked by activation of dorsomedial hypothalamus neurons is largely dependent on a synaptic relay with the lateral/dorsolateral periaqueductal gray region. In this study, we aimed to investigate whether excitatory amino acid receptors at the lateral/dorsolateral periaqueductal gray region are involved in mediating the response evoked by activation of dorsomedial hypothalamus neurons. In conscious rats, the cardiovascular effects produced by microinjection of GABA(A) receptor antagonist, bicuculline methiodide into the dorsomedial hypothalamus were evaluated before and after injection of different excitatory amino acid antagonists into lateral/dorsolateral periaqueductal gray region. Pretreatment of lateral/dorsolateral periaqueductal gray region with the non-selective ionotropic excitatory amino acid receptor antagonist kynurenic acid or with the N-methyl-D-aspartate receptor-selective antagonist, MK-801, largely reduced the tachycardic and pressor effects evoked by activation of dorsomedial hypothalamus neurons by bicuculline methiodide microinjection (heart rate 90 and 74%; blood pressure 81 and 84%, respectively). The non-N-methyl-D-aspartate receptor-selective antagonist 6-cyano-7-nitroquinoxaline-2,3-dione, did not alter the cardiovascular response evoked by dorsomedial hypothalamus activation. In an additional series of experiments, microinjection of the N-methyl-D-aspartate receptor agonist, N-methyl-D-aspartate, into the lateral/dorsolateral periaqueductal gray region, evoked an increase in heart rate and a pressor response that was accompanied by an increase in locomotor activity. These effects were not altered by pretreatment of lateral/dorsolateral periaqueductal gray region neurons with 6-cyano-7-nitroquinoxaline-2,3-dione but were completely abolished by MK-801. Altogether, these findings indicate that the cardiovascular response evoked by dorsomedial hypothalamus activation involves a synaptic relay at the lateral/dorsolateral periaqueductal gray region that is mediated at least in large part by excitatory amino acid receptors, possibly N-methyl-D-aspartate receptors.
Assuntos
Antagonistas de Aminoácidos Excitatórios/administração & dosagem , Hipotálamo/efeitos dos fármacos , Vias Neurais/metabolismo , Substância Cinzenta Periaquedutal/metabolismo , Receptores de Glutamato/metabolismo , Animais , Bicuculina/administração & dosagem , Pressão Sanguínea/efeitos dos fármacos , Sistema Cardiovascular , Maleato de Dizocilpina/administração & dosagem , Hipotálamo/metabolismo , Injeções Intraventriculares , Masculino , Microinjeções , Atividade Motora/efeitos dos fármacos , Vias Neurais/efeitos dos fármacos , Neurônios/efeitos dos fármacos , Neurônios/metabolismo , Substância Cinzenta Periaquedutal/efeitos dos fármacos , Ratos , Ratos Wistar , Receptores de Glutamato/efeitos dos fármacos , Taquicardia/induzido quimicamenteRESUMO
Based on complementary metal-oxide semiconductor (CMOS) technology a neurosensor chip with passive palladium electrodes was developed. The CMOS technology allows a high reproducibility of the sensors as well as miniaturization and the on-chip integration of electronics. Networks of primary neurones were taken from murine foetal spinal cord (day 14) and frontal cortex (day 15) tissues and cultured on the silicon surface in a chamber volume of 200 microl with 7 mm diameter. Measurements were performed between days 15 and 59 in vitro. Signals were recorded from both types of cultures. To test the capability of the system to detect pharmacologically induced activity changes two established neuromodulators were applied. The GABA(A)-receptor blocker bicuculline was applied to both tissue cultures, the glycine-receptor blocker strychnine to spinal cord cultures. Four network frequency parameters were analysed: spike rate (SR), burst rate (BR), frequency in bursts (FiB) and peak frequency in bursts (PFiB). Significant changes of spike rate and burst rate were measured with spinal cord cultures after bicuculline application. Significant changes of frequency in bursts and peak frequency in bursts were observed with frontal cortex cultures after bicuculline application. Significant changes of spike rate and frequency in bursts were recorded with spinal cord cultures after strychnine application. These results were compared with results achieved in the same laboratory by using glass-microelectrode arrays (MEAs). This comparison showed for spinal cord similar native spike and burst rate, but higher mean frequency and peak frequency in bursts, whereas frontal cortex activity had higher spike and burst rate and peak frequency in bursts. Application of bicuculline or strychnine to spinal cord networks showed stronger effects on MEAs, whereas with frontal cortex networks the modulation of activity was similar after application of bicuculline.
Assuntos
Potenciais de Ação/fisiologia , Amplificadores Eletrônicos , Bioensaio/instrumentação , Técnicas Biossensoriais/instrumentação , Rede Nervosa/fisiologia , Neurônios/fisiologia , Potenciais de Ação/efeitos dos fármacos , Animais , Bicuculina/administração & dosagem , Bioensaio/métodos , Técnicas Biossensoriais/métodos , Técnicas de Cultura de Células/instrumentação , Técnicas de Cultura de Células/métodos , Células Cultivadas , Desenho de Equipamento , Análise de Falha de Equipamento , Camundongos , Microeletrodos , Rede Nervosa/efeitos dos fármacos , Neurônios/efeitos dos fármacos , Semicondutores , Estricnina/administração & dosagem , Fatores de TempoRESUMO
The hypothalamic paraventricular nucleus (PVN) plays an important role in the sympathoexcitatory response to elevated plasma angiotensin II (Ang II). However, the mechanism by which Ang II influences sympathetic activity is not fully understood. In this study, we tested the hypothesis that GABA(gamma-aminobutyric acid)-ergic function in the PVN is reduced by peripheral infusion of Ang II. To accomplish this, rats received either intravenous Ang II (12 ng/kg per minute) or vehicle (D5W) for 7 days, and renal sympathetic nerve activity (SNA), mean arterial pressure (MAP), and heart rate (HR) responses were recorded after unilateral PVN microinjection of the GABA-A receptor antagonist bicuculline methiodide (BMI, 0.1 nmol). Results indicate that in contrast to a significant increase in renal SNA, MAP, and HR observed in vehicle-infused rats (P<0.05), BMI injection into the PVN of Ang II-infused animals was without effect on all recorded variables. In a separate groups of animals, ganglionic blockade produced a significantly greater fall in MAP (P<0.01) in Ang II-infused rats than in vehicle-infused control rats, indicating that the contribution of SNA to the maintenance of blood pressure was elevated in the Ang II-infused group. Overall, these data indicate that cardiovascular and sympathoexcitatory responses to acute GABA-A receptor antagonism in the PVN are significantly blunted in rats after 7 days of intravenous infusion of Ang II. We conclude that an Ang II-induced reduction in GABAergic inhibition within the PVN may contribute to elevated SNA observed in this study.
Assuntos
Angiotensina II/farmacologia , Bicuculina/análogos & derivados , Bicuculina/farmacologia , Antagonistas GABAérgicos/farmacologia , Núcleo Hipotalâmico Paraventricular/fisiologia , Angiotensina II/administração & dosagem , Animais , Bicuculina/administração & dosagem , Bicuculina/antagonistas & inibidores , Pressão Sanguínea/efeitos dos fármacos , Clorisondamina/farmacologia , Antagonistas GABAérgicos/administração & dosagem , Antagonistas de Receptores de GABA-A , Bloqueadores Ganglionares/farmacologia , Frequência Cardíaca/efeitos dos fármacos , Hipotálamo/anatomia & histologia , Infusões Intravenosas , Injeções , Rim/inervação , Masculino , Núcleo Hipotalâmico Paraventricular/efeitos dos fármacos , Ratos , Ratos Sprague-Dawley , Sistema Nervoso Simpático/efeitos dos fármacos , Sistema Nervoso Simpático/fisiologiaRESUMO
Acute blockade of gamma-aminobutyric acid (GABA)-A receptors in the hypothalamic paraventricular nucleus (PVN) increases mean arterial pressure (MAP), heart rate (HR), and sympathetic nerve activity (SNA). However, the underlying neural mechanisms have not been fully determined. We tested the hypothesis that responses to GABA-A receptor blockade in the PVN require activation of local ionotropic excitatory amino acid (EAA) receptors. MAP, HR, and renal SNA responses to unilateral PVN microinjection of bicuculline methobromide (BIC, 0.1 nmol) were recorded before and after ipsilateral PVN injection of either vehicle (saline), the nonselective ionotropic EAA receptor antagonist kynurenate (KYN), the NMDA receptor antagonist D(-)-2-amino-5-phosphonopentanoic acid (AP5), or the non-NMDA receptor antagonist 2,3-dioxo-6-nitro-1,2,3,4-tetrahydrobenzo[f]quinoxaline-7-sulfonamide disodium (NBQX). Responses to PVN-injected BIC were unaltered by vehicle injection. In contrast, injection of KYN (7.2 nmol; n=4) nearly abolished ABP and renal SNA responses to BIC (P<0.01) and significantly attenuated (P<0.05) HR responses as well. Similarly, graded doses of AP5 (0.6, 3, and 6 nmol) and NBQX (0.26, 1.3, and 2.6 nmol) reduced responses to PVN-injected BIC in a dose-related manner, with the 3 nmol (n=7) and 1.3 nmol (n=6) doses producing maximal effects (P<0.05). KYN, AP5, and NBQX did not affect baseline parameters. Effects of a cocktail containing AP5 (3 nmol) and NBQX (1.3 nmol) were greater (P<0.01) than either antagonist alone and were not statistically different from KYN. These data indicate that cardiovascular and renal sympathetic responses to acute GABA-A receptor blockade in the PVN require local actions of EAAs at both NMDA and non-NMDA receptors.
Assuntos
Bicuculina/farmacologia , Antagonistas GABAérgicos/farmacologia , Núcleo Hipotalâmico Paraventricular/fisiologia , Receptores de Glutamato/metabolismo , Sistema Nervoso Simpático/fisiologia , 2-Amino-5-fosfonovalerato/farmacologia , Animais , Bicuculina/administração & dosagem , Pressão Sanguínea/efeitos dos fármacos , Antagonistas de Aminoácidos Excitatórios/farmacologia , Antagonistas GABAérgicos/administração & dosagem , Antagonistas de Receptores de GABA-A , Frequência Cardíaca/efeitos dos fármacos , Hipotálamo/anatomia & histologia , Injeções , Rim/inervação , Ácido Cinurênico/farmacologia , Masculino , Núcleo Hipotalâmico Paraventricular/efeitos dos fármacos , Quinoxalinas/farmacologia , Ratos , Ratos Sprague-Dawley , Receptores de N-Metil-D-Aspartato/antagonistas & inibidores , Sistema Nervoso Simpático/efeitos dos fármacosRESUMO
Loreclezole (5 mg/kg) exerted a significant protective action in amygdala-kindled rats, reducing both seizure and afterdischarge durations. The combinations of loreclezole (2.5 mg/kg) with valproate, clonazepam, or carbamazepine (applied at their subprotective doses) also exhibited antiseizure effect in this test. However, only two first combinations occurred to be of pharmacodynamic nature. Among several chemoconvulsants, bicuculline, N-methyl-D-aspartic acid and BAY k-8644 (the opener of L-type calcium channels) reversed the protective activity of loreclezole alone and its combination with valproate. On the other hand, bicuculline, aminophylline and BAY k-8644 inhibited the anticonvulsive action of loreclezole combined with clonazepam. The results support the hypothesis that the protective activity of loreclezole and its combinations with other antiepileptics may involve potentiation of GABAergic neurotransmission and blockade of L-type of calcium channels.
Assuntos
Tonsila do Cerebelo/efeitos dos fármacos , Convulsivantes/efeitos adversos , Combinação de Medicamentos , Excitação Neurológica/efeitos dos fármacos , Triazóis/antagonistas & inibidores , Triazóis/uso terapêutico , Éster Metílico do Ácido 3-Piridinacarboxílico, 1,4-Di-Hidro-2,6-Dimetil-5-Nitro-4-(2-(Trifluormetil)fenil)/farmacologia , Aminofilina/administração & dosagem , Aminofilina/efeitos adversos , Aminofilina/farmacocinética , Tonsila do Cerebelo/fisiopatologia , Tonsila do Cerebelo/cirurgia , Animais , Bicuculina/administração & dosagem , Bicuculina/efeitos adversos , Bicuculina/farmacocinética , Carbamazepina/farmacologia , Clonazepam/antagonistas & inibidores , Clonazepam/farmacologia , Convulsivantes/administração & dosagem , Convulsivantes/antagonistas & inibidores , Modelos Animais de Doenças , Interações Medicamentosas , Eletrodos Implantados , Injeções Intraperitoneais , Ácido Caínico/administração & dosagem , Ácido Caínico/farmacocinética , Masculino , N-Metilaspartato/administração & dosagem , N-Metilaspartato/efeitos adversos , N-Metilaspartato/farmacocinética , Ratos , Ratos Wistar , Convulsões/induzido quimicamente , Convulsões/fisiopatologia , Convulsões/prevenção & controle , Técnicas Estereotáxicas , Estricnina/administração & dosagem , Estricnina/efeitos adversos , Estricnina/farmacocinética , Fatores de Tempo , Triazóis/administração & dosagem , Ácido Valproico/administração & dosagem , Ácido Valproico/antagonistas & inibidores , Ácido Valproico/farmacocinéticaRESUMO
The main goal of this article is to review the key role that the inferior colliculus plays in the expression of acoustic-motor and acoustic-limbic integration involved, respectively, in acute and chronic audiogenic seizures. In order to put this in context, we will review the behavioral characterization of acute and chronic audiogenic seizures, neuroanatomical substrates, neurochemistry, neuropharmacology, electrophysiology, as well as the cellular and molecular mechanisms involved in their expression. Secondly, we will also correlate our results, collected from audiogenic seizures susceptible rats, before and after the genetic selection of our own audiogenic susceptible strain, and from those sensitized by lesions or drug microinjections, with those pertinent from the international literature. In brief, genetic or sensitized animals express acute audiogenic seizures as a wild running behavior preceding the onset of tonic-clonic seizures. The latter can have several presentations including opistotonus and fore- and hindlimb tonic hyperextensions, followed by clonic convulsions of fore- and hindlimbs. Chronic (kindled) audiogenic seizures change this behavioral expression, with similar patterns such as those present in temporal lobe epileptic seizures, intermingled with the original audiogenic seizure pattern, which is known to be dependent on brainstem networks.