RESUMO
Substance P (SP) is a highly conserved member of the tachykinin peptide family that is widely expressed throughout the animal kingdom. The numerous members of the tachykinin peptide family are involved in a multitude of neuronal signaling pathways, mediating sensations and emotional responses (Steinhoff et al. in Physiol Rev 94:265-301, 2014). In contrast to receptors for classical transmitters, such as glutamate (Parsons et al. in Handb Exp Pharmacol 249-303, 2005), only a minority of neurons in certain brain areas express neurokinin receptors (NKRs) (Mantyh in J Clin Psychiatry 63:6-10, 2002). SP is also expressed by a variety of non-neuronal cell types such as microglia, as well as immune cells (Mashaghi et al. in Cell Mol Life Sci 73:4249-4264, 2016). SP is an 11-amino acid neuropeptide that preferentially activates the neurokinin-1 receptor (NK1R). It transmits nociceptive signals via primary afferent fibers to spinal and brainstem second-order neurons (Cao et al. in Nature 392:390-394, 1998). Compounds that inhibit SP's action are being investigated as potential drugs to relieve pain. More recently, SP and NKR have gained attention for their role in complex psychiatric processes. It is a key goal in the field of pain research to understand mechanisms involved in the transition between acute pain and chronic pain. The influence of emotional and cognitive inputs and feedbacks from different brain areas makes pain not only a perception but an experience (Zieglgänsberger et al. in CNS Spectr 10:298-308, 2005; Trenkwaldner et al. Sleep Med 31:78-85, 2017). This review focuses on functional neuronal plasticity in spinal dorsal horn neurons as a major relay for nociceptive information.
Assuntos
Dor Crônica/metabolismo , Substância P/metabolismo , Animais , Humanos , Memória , Modelos Biológicos , Rede Nervosa/metabolismo , NociceptividadeRESUMO
In a direct approach to elucidate the origin of long-term depression (LTD), glutamate was applied onto dendrites of neurons in rat neocortical slices. An infrared-guided laser stimulation was used to release glutamate from caged glutamate in the focal spot of an ultraviolet laser. A burst of light flashes caused an LTD-like depression of glutamate receptor responses, which was highly confined to the region of "tetanic" stimulation (<10 micrometers). A similar depression of glutamate receptor responses was observed during LTD of synaptic transmission. A spatially highly specific postsynaptic mechanism can account for the LTD induced by glutamate release.
Assuntos
Neocórtex/fisiologia , Plasticidade Neuronal , Células Piramidais/fisiologia , Receptores de Glutamato/metabolismo , Sinapses/fisiologia , Transmissão Sináptica , Animais , Maleato de Dizocilpina/farmacologia , Estimulação Elétrica , Antagonistas de Aminoácidos Excitatórios/farmacologia , Potenciais Pós-Sinápticos Excitadores , Glutamatos/farmacologia , Ácido Glutâmico/metabolismo , Técnicas In Vitro , Raios Infravermelhos , Lasers , Microscopia de Vídeo , Neocórtex/citologia , Técnicas de Patch-Clamp , Fotólise , Ratos , Ratos Sprague-Dawley , Receptores de N-Metil-D-Aspartato/antagonistas & inibidores , Receptores de N-Metil-D-Aspartato/metabolismoRESUMO
The atypical excitation by opiates and opioid peptides of hippocampal pyramidal cells can be antagonized by iontophoresis of naloxone, the gamma-aminobutyric acid antagonists bicuculline, or magnesium ion. The recurrent inhibition of these cells evoked by transcallosal stimulation of the contralateral hippocampus is blocked by enkephalin but only shortened by acetylcholine. The results suggest that the opioids excite pyramidal neurons indirectly by inhibition of neighboring inhibitory interneurons (probably containing gamma-aminobutyric acid). This mechanism may be pertinent to the electrographic signs of addictive drugs.
Assuntos
Endorfinas/farmacologia , Encefalinas/farmacologia , Hipocampo/fisiologia , Neurônios/fisiologia , Animais , Bicuculina/farmacologia , Hipocampo/efeitos dos fármacos , Magnésio/farmacologia , Neurônios/efeitos dos fármacos , RatosRESUMO
BACKGROUND: Visual analgesia refers to the phenomena where people report decreased pain intensity when they see the painful or painfully stimulated body part. Alongside pain, sensorimotor impairment (i.e., disturbed proprioception) is also evident in chronic pain. This study aims to investigate whether real-time visual feedback offers additional pain relief and proprioceptive improvement when used in combination with recommended therapies in neck pain patients who received manual therapy with or without real-time visual feedback. METHODS: A total of 29 neck pain patients were recruited in an outpatient physical therapy practice. Patients were randomly allocated to receive manual therapy of the cervical spine with real-time visual feedback or to a control group where patients received manual therapy without real-time visual feedback. Habitual pain intensity, the pressure pain threshold at the zygapophyseal joint of C2-C3 and the superior angle of the scapulae and cervical proprioception were assessed before and immediately after the intervention by a blinded assessor. RESULTS: A between-group comparison revealed a significant reduction in habitual pain in the real-time visual feedback group. No differences were found for the pressure pain threshold or proprioceptive performance. CONCLUSIONS: Real-time visual feedback combined with manual therapy enhanced the analgesic effect of manual therapy in neck pain patients, but had no positive effect on the pressure pain threshold and cervical joint position sense. The technical demands for integrating real-time visual feedback into daily practice to reduce habitual pain are low, have low costs and are easy to apply. SIGNIFICANCE: Real-time visual feedback reduces habitual pain immediately after the intervention. Due to its easy integration, it may be an effective adjunct to recommended interventions (i.e., manual therapy) in patients with neck pain.
Assuntos
Dor Crônica/terapia , Retroalimentação Sensorial , Manipulações Musculoesqueléticas , Cervicalgia/terapia , Pescoço , Propriocepção , Adulto , Dor Crônica/fisiopatologia , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Cervicalgia/fisiopatologia , Manejo da Dor , Medição da Dor , Limiar da Dor , Modalidades de Fisioterapia , Articulação ZigapofisáriaRESUMO
Several 3 alpha-hydroxysteroids accumulate in the brain after local synthesis or after metabolization of steroids that are provided by the adrenals. The 3 alpha-hydroxy ring A-reduced pregnane steroids allopregnanolone and tetrahydrodeoxycorticosterone are believed not to interact with intracellular receptors, but enhance GABA-mediated chloride currents. The present study shows that these neuroactive steroids can regulate gene expression via the progesterone receptor. The induction of DNA binding and transcriptional activation of the progesterone receptor requires intracellular oxidation of the neuroactive steroids into progesterone receptor active 5 alpha-pregnane steroids. Thus, at physiological concentrations, these neuroactive steroids regulate neuronal function through their effects on both transmitter-gated ion channels and steroid receptor-regulated gene expression.
Assuntos
Desoxicorticosterona/análogos & derivados , Pregnanolona/farmacologia , Receptores de Progesterona/fisiologia , Sequência de Bases , DNA/metabolismo , Desoxicorticosterona/metabolismo , Desoxicorticosterona/farmacologia , Regulação da Expressão Gênica/efeitos dos fármacos , Humanos , Membranas Intracelulares/metabolismo , Dados de Sequência Molecular , Neurônios/fisiologia , Oxirredução , Pregnanolona/metabolismo , Receptores de Progesterona/efeitos dos fármacos , Receptores de Progesterona/metabolismo , Esteroides/química , Esteroides/metabolismo , Células Tumorais CultivadasRESUMO
BACKGROUND: Previous findings suggest that watching sites of experimental and chronic pain can exert an analgesic effect. Our present study investigates whether watching one's back during massage increases the analgesic effect of this treatment in chronic back pain patients. METHODS: Twenty patients with chronic back pain were treated with a conventional massage therapy. During this treatment, patients received a real-time video feedback of their own back. Watching a neutral object, a video of another person of the same sex being massaged, a picture of the own back, and keeping one's eyes closed were used as controls. These conditions were presented in randomized order on five separate days. RESULTS: All conditions yielded significant decreases in habitual pain intensity. The effect of real-time video feedback of the own back on massage treatment was the strongest and differed significantly from the effect of watching a neutral object, but not from the other control conditions, which may have induced slight effects of their own. CONCLUSIONS: Repeated real-time video feedback may be useful during massage treatment of chronic pain. SIGNIFICANCE: This study shows that inducing visual induced analgesia during massage treatment can be helpful in alleviating chronic pain.
Assuntos
Analgesia/métodos , Dor Crônica/terapia , Retroalimentação Sensorial , Dor Lombar/terapia , Massagem/métodos , Adulto , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Medição da Dor , Resultado do TratamentoRESUMO
Brain slices were introduced as a standard preparation for neurophysiological experiments some 20 years ago. A drawback of this preparation compared with cell culture has been the difficulty to visualize individual neurones in standard thick slices. This problem has been overcome by the use of infrared videomicroscopy. Neurones in slices can now be visualized in great detail, and neuronal processes can be patch-clamped under direct visual control. Infrared video-microscopy has also been applied successfully to other fields of neuroscience such as neuronal development and neurotoxicity. A further development of infrared videomicroscopy enables one to visualize the spread of excitation in slices making the technique a tool for the direct investigation of neuronal function.
Assuntos
Raios Infravermelhos , Microscopia de Vídeo/métodos , Neurônios/fisiologia , Neurônios/ultraestrutura , Animais , Encéfalo/citologia , Encéfalo/fisiologia , Morte Celular , Movimento Celular , Eletrofisiologia/métodos , Previsões , Humanos , Técnicas In Vitro , Neurônios/efeitos dos fármacos , Neurotoxinas/farmacologiaRESUMO
Recent advances in pain research illustrate the analytical power of modern neurosciences in a field previously accessible only to methods of systems biology. Novel molecular and cellular biological techniques have changed the face of pain research by detailing the multiplicity of pain transducing and pain suppressive systems which involve neuronal and hormonal systems acting in concert to help the individual to cope with pain. The introduction of concepts of neuronal plasticity in this field has led to important therapeutical consequences. Novel compounds and new regimens for drug treatment to prevent activity-dependent long-term changes or to facilitate extinction in pain-related systems are emerging.
Assuntos
Neurônios/fisiologia , Dor/fisiopatologia , Transdução de Sinais , Medula Espinal/fisiologia , Analgésicos/farmacologia , Animais , Endorfinas/fisiologia , Humanos , Modelos Biológicos , Neurônios/efeitos dos fármacos , Neuropeptídeos/fisiologia , Nociceptores/fisiologia , Receptores de Glutamato/fisiologia , Receptores de N-Metil-D-Aspartato/fisiologia , Medula Espinal/fisiopatologiaRESUMO
BACKGROUND: Chronic back pain (CBP) is a frequent debilitating and often treatment-resistant disorder. The awareness of one's own body seems to be essential in pain reduction through visual input. Visual feedback of the back reduces experimental pain perception in CBP at this site and watching the back during repeated lumbar spine movements reduces movement-evoked pain. In this study, we tested whether visual feedback alone can reduce habitual pain in CBP. METHODS: In a within-subject design, 19 CBP patients participated in an online visual feedback condition, watching one's own back. This was compared to several control conditions, such as watching a neutral object (book), a video of another person of the same sex, a picture of the own back, and keeping one's eyes closed in randomized order on five separate days. In each experimental session, participants rated habitual pain intensity and unpleasantness before and after the experimental manipulation. RESULTS: We present evidence that visual feedback by watching the site of chronic pain on a video screen alone is sufficient to reduce habitual chronic pain. No additional manipulation or movement was necessary. CONCLUSIONS: These results suggest that online video feedback may be helpful in alleviating chronic pain.
Assuntos
Dor nas Costas/psicologia , Dor nas Costas/terapia , Dor Crônica/psicologia , Dor Crônica/terapia , Retroalimentação Sensorial , Adulto , Feminino , Humanos , Vértebras Lombares , Masculino , Pessoa de Meia-Idade , Movimento , Medição da Dor , Resultado do TratamentoRESUMO
Anti-craving compounds have recently been registered for relapse prophylaxis in weaned alcoholics in various European countries (acamprosate), and in the United States (naltrexone). Acamprosate, the Ca(2+)-salt of N-acetyl-homotaurinate, interacts with NMDA receptor-mediated glutamatergic neurotransmission in various brain regions and reduces Ca2+ fluxes through voltage-operated channels. The opioid receptor antagonist naltrexone most likely interferes with alcohol-induced reinforcement via the block of opioid receptors. In this article Rainer Spanagel and Walter Zieglgänsberger discuss the pivotal role of incremental neuroadaptation to alcohol and alcohol-associated stimuli for craving, and the possible mechanisms of action underlying the anti-craving properties of acamprosate and naltrexone.
Assuntos
Alcoolismo/tratamento farmacológico , Naltrexona/uso terapêutico , Antagonistas de Entorpecentes/uso terapêutico , Taurina/análogos & derivados , Acamprosato , Animais , Comportamento Animal/efeitos dos fármacos , Canais de Cálcio/efeitos dos fármacos , Modelos Animais de Doenças , Humanos , Naltrexona/administração & dosagem , Naltrexona/farmacologia , Antagonistas de Entorpecentes/administração & dosagem , Antagonistas de Entorpecentes/farmacologia , Neurônios/citologia , Neurônios/efeitos dos fármacos , Ratos , Receptores de N-Metil-D-Aspartato/antagonistas & inibidores , Receptores Opioides/efeitos dos fármacos , Recidiva , Síndrome de Abstinência a Substâncias/tratamento farmacológico , Transmissão Sináptica/efeitos dos fármacos , Taurina/administração & dosagem , Taurina/farmacologia , Taurina/uso terapêuticoRESUMO
BACKGROUND: The effectiveness of acamprosate (calcium bisacetylhomotaurinate) as a treatment to maintain abstinence in alcohol-dependent patients was assessed for 1 year. METHODS: After short-term detoxification, 272 patients participated in a randomized, double-blind, placebo-controlled study. Patients received routine counseling and either the study medication or placebo for 48 weeks; they were followed up for another 48 weeks without medication. Statistical analysis was performed according to the intention-to-treat principle. RESULTS: Patients who were receiving acamprosate showed a significantly higher continuous abstinence rate within the first 60 days of treatment compared with patients who were assigned to placebo treatment (67% vs 50%) until completion of the treatment period (43% vs 21%, log rank P = .005), and they had a significantly longer mean abstinence duration of 224 vs 163 days, or 62% vs 45% days abstinent (P < .001); however, there was no difference in psychiatric symptoms. Of the patients who were receiving acamprosate, 41% had dropped out, whereas 60% of the placebo-treated patients dropped out of the study. Few side effects (mainly diarrhea and headache) were recorded. At the end of a further 48 weeks without receiving study medication, 39% and 17% of the acamprosate- and placebo-treated patients, respectively, had remained abstinent (P = .003). CONCLUSION: Acamprosate proved to be a safe and effective aid in treating alcohol-dependent patients and in maintaining the abstinence of patients during 2 years.
Assuntos
Alcoolismo/prevenção & controle , Taurina/análogos & derivados , Acamprosato , Adulto , Idoso , Consumo de Bebidas Alcoólicas/prevenção & controle , Método Duplo-Cego , Feminino , Seguimentos , Humanos , Masculino , Pessoa de Meia-Idade , Pacientes Desistentes do Tratamento , Placebos , Recidiva , Análise de Sobrevida , Taurina/uso terapêutico , Temperança , Resultado do TratamentoRESUMO
Steroid hormone action involves binding to cognate intracellular receptors that, in turn, bind to respective response elements and thus modulate gene expression. The present study shows that the gonadal steroids, 17beta-estradiol and progesterone, may also act as functional antagonists at the 5-hydroxytryptamine type 3 (5-HT3) receptor in whole-cell voltage-clamp recordings of HEK 293 cells stably expressing the 5-HT3 receptor. Functional antagonistic properties at this ligand-gated ion channel could also be shown for 17alpha-estradiol, 17alpha-ethinyl-17beta-estradiol, mestranol, R 5020, testosterone, and allopregnanolone but not for pregnenolone sulfate and cholesterol. An antagonism at the 5-HT3 receptor could further be observed with the aromatic alcohol 4-dodecylphenol but not with phenol or ethanol. Thus, the modulation of 5-HT3 receptor function by steroids or alcohols is dependent on their respective molecule structure. The antagonistic action of steroids at the 5-HT3 receptor is not mediated via the serotonin binding site because the steroids did not alter the binding affinity of [3H]GR65630 to the 5-HT3 receptor, and kinetic experiments revealed a quite different response pattern to 17beta-estradiol when compared with the competitive antagonist metoclopramide. BSA-conjugated gonadal steroids labeled with fluorescein isothiocyanate bound to membranes of HEK 293 cells expressing the 5-HT3 receptor in contrast to native HEK 293 cells. However, there was no dose-dependent displacement of the binding of gonadal steroids to membranes of cells expressing the 5-HT3 receptor in binding experiments or fluorescence studies. Thus, gonadal steroids probably interact allosterically with the 5-HT3 receptor at the receptor-membrane interface. The functional antagonism of gonadal steroids at the 5-HT3 receptor may play a role for the development and course of nausea during pregnancy and of psychiatric disorders.
Assuntos
Estradiol/fisiologia , Progesterona/fisiologia , Receptores de Serotonina/metabolismo , Antagonistas da Serotonina/metabolismo , Linhagem Celular , Potenciais Evocados , Feminino , Humanos , Imidazóis/metabolismo , Indóis/metabolismo , Rim/embriologia , Rim/fisiologia , Gravidez , Receptores 5-HT3 de Serotonina , TransfecçãoRESUMO
In recent years great progress has been made in understanding the function of ionotropic and metabotropic glutamate receptors; their pharmacology and potential therapeutic applications. It should be stressed that there are already N-methyl-D-aspartate (NMDA) antagonists in clinical use, such as memantine, which proves the feasibility of their therapeutic potential. It seems unlikely that competitive NMDA receptor antagonists and high-affinity channel blockers will find therapeutic use due to limiting side-effects, whereas agents acting at the glycineB site, NMDA receptor subtype-selective agents and moderate-affinity channel blockers are far more promising. This is supported by the fact that there are several glycineB antagonists, NMDA moderate-affinity channel blockers and NR2B-selective agents under development. Positive and negative modulators of AMPA receptors such as the AMPAkines and 2,3-benzodiazepines also show more promise than e.g. competitive antagonists. Great progress has also been made in the field of metabotropic glutamate receptors since the discovery of novel, allosteric modulatory sites for these receptors. Selective agents acting at these transmembrane sites have been developed that are more drug-like and have a much better access to the central nervous system than their competitive counterparts. The chapter will critically review preclinical and scarce clinical experience in the development of new ionotropic and metabotropic glutamate receptor modulators according to the following scheme: rational, preclinical findings in animal models and finally clinical experience, where available.
Assuntos
Aminoácidos Excitatórios/fisiologia , Receptores de Glutamato/fisiologia , Transmissão Sináptica/fisiologia , Animais , Humanos , Doenças do Sistema Nervoso/fisiopatologia , Plasticidade NeuronalRESUMO
The effects of somatostatin (SS14) on neocortical neurons of the rat were investigated in an in vitro slice preparation. Intracellular recordings were performed in neurons (n=30) in layers 2 and 3 of the frontal cortex. Iontophoretically applied SS14 reduced the responses evoked by iontophoretically applied L-glutamate (GLU) and gamma-aminobutyric acid (GABA). The blocking effect of SS14 was apparent 1 - 2 min after onset of SS14 application and recovery required 2 - 3 min. The conductance increase evoked by GLU or GABA was reduced by SS14. In the majority of neurons, SS14 did not produce any measurable changes in passive membrane properties, spike threshold or on orthodromically evoked synaptic potentials. In 5 cells, SS14 induced a slight hyperpolarization (<3 mV). These results lend further support to claims that SS14 plays a neuromodulatory role in the neocortex.
RESUMO
Extracellular recordings were obtained of 177 neurons throughout the lumbar spinal dorsal horn of urethane- or halothane-anesthetized rats. These neurons all responded to iontophoretically applied L-glutamate and their responses to natural stimulation of the ipsilateral hindlimb were characterized. Iontophoretically applied norepinephrine was tested on 94 of these neurons. Fifty-one neurons were inhibited and 22 were excited. Norepinephrine produced a biphasic inhibitory/excitatory effect on nine neurons. Norepinephrine was exclusively inhibitory on superficial dorsal horn neurons that responded only to innocuous brush and touch and on neurons in the nucleus proprius that responded to brush, touch, and noxious skin pinch. Norepinephrine excited some superficial brush/touch/pinch neurons and produced short inhibitions that were followed by prolonged excitations of some nucleus proprius neurons that responded only to noxious skin pinch. Neurons in the base of the dorsal horn that responded to low-threshold proprioceptive stimulation were excited by norepinephrine. Both the inhibitory and excitatory effects of norepinephrine were stereoselective, but they were not blocked by receptor subtype-selective antagonists. Desensitization to norepinephrine occurred for 30% of the neurons. This study demonstrates that the inhibitory effects of norepinephrine on rat dorsal horn neurons are not restricted to neurons that are responsive to noxious stimuli and that some of these neurons are primarily excited by norepinephrine. The excitatory effects of norepinephrine on low-threshold proprioceptive neurons may contribute to norepinephrine's known enhancement of spinal flexor reflex activity.
Assuntos
Potenciais Somatossensoriais Evocados , Norepinefrina/farmacologia , Medula Espinal/fisiologia , Potenciais de Ação/efeitos dos fármacos , Animais , Potenciais Somatossensoriais Evocados/efeitos dos fármacos , Interneurônios/efeitos dos fármacos , Interneurônios/fisiologia , Fentolamina/farmacologia , Propriocepção/fisiologia , Ratos , Medula Espinal/citologia , Estereoisomerismo , Relação Estrutura-Atividade , Ioimbina/farmacologiaRESUMO
The fine structure and synaptic architecture of the afferent terminations in dorsal horn lamina II are studied using a combined light and electron microscopic procedure after anterograde labelling with horseradish peroxidase. Vibratome parasagittal sections, stained with heavy metal intensified diaminobenzidine after tracer application to the dorsal roots, were flat-embedded in Epon. The five types of labelled terminal arbors occurring in lamina IIi (Cruz et al., '87: J. Comp. Neurol. 261:221-236) were drawn and relocated in 5-microns sections cut serially from the thick sections. Ultrathin sections were then cut from the 5-microns sections so that the terminal fibers and swellings observed in the light microscope could be traced in the electron microscope. The flame-shaped arbors arose from fine myelinated stem fibers. Terminal strands generated large oval central terminals of type II synaptic glomeruli (CII), which established frequent axoaxonal contacts. Similar terminals have been labelled in the cat after tracer injections into hair-follicle fibers (Réthelyi et al., '82: J. Comp. Neurol. 207:381-393). The other four plexuses arose from unmyelinated stem fibers. The swarms of ultrafine boutons consisted of extremely thin terminal fibers generating very small, round, or polygonal glomerular terminals containing tightly packed agranular synaptic vesicles of variable size and one mitochondrion at best. The terminal strands of the bouquet plexus bore long and scalloped central varicosities of type I synaptic glomeruli (CI) with pleomorphic agranular vesicles and a relative abundance of dendroaxonal contacts. These features, together with the location in dorsal lamina IIi, suggest their belonging to the fluoride resistant acid phosphatase (FRAP)-reactive population. The boutons of the undulating fibers and those of the lateral plexus were, like those of the bouquets, scalloped and elongated rostrocaudally (CI), but contained a few large granular vesicles. The occurrence of the swarm, undulating, and lateral plexuses in ventral lamina IIi, which seems to lack FRAP or peptidergic terminals, suggests an origin from other, still unidentified neurochemical populations of fine primary afferents.
Assuntos
Neurônios Aferentes/ultraestrutura , Medula Espinal/citologia , Sinapses/ultraestrutura , Animais , Peroxidase do Rábano Silvestre , Microscopia Eletrônica , Terminações Nervosas/ultraestrutura , Ratos , Ratos Endogâmicos , Medula Espinal/ultraestruturaRESUMO
The convulsant effects of alpha-thujone, the psychotropic component of absinthe, were attributed to inhibitory actions at the GABAA receptor. Here, we investigated for the first time the 5-HT3 receptor as a potential site of the psychotropic actions of alpha-thujone. This cation permeable ligand-gated ion channel shows considerable homology to the GABAA receptor. We previously demonstrated that in homomeric assemblies of cloned human 5-HT,A receptor subunits. the endogenous agonist 5-HT induced desensitization via channel blockade. When the 5-HT3 B receptor subunit was co-expressed, the resulting heteromeric assemblies desensitized independent from channel blockade. In the present study, patch-clamp experiments revealed an inhibitory action of alpha-thujone on both homomeric and heteromeric 5-HT3 receptors. This inhibitory action was mediated via channel blockade. However, it was not alpha-thujone itself which blocked the channel. The present experiments suggested that, in homomeric receptors, alpha-thujone enhanced the inherent channel-blocking potency of the natural ligand. 5-HT. In heteromeric receptors, alpha-thujonerecruited an additional channel-blocking component of the agonist. By means of kinetic modeling, we simulated possible mechanisms by which alpha-thuljone decreased the 5-HT-induced responses. It is suggested that alpha-thujone reduced 5-HT3 receptor activity by an effect on mechanisms involved in receptor desensitization, which depend on receptor subunit composition. It remains to be shown if this inhibitory action on serotonergic responses contributes to behavioral effects of alpha-thujone.
Assuntos
Monoterpenos/farmacologia , Receptores 5-HT3 de Serotonina/metabolismo , Agonistas do Receptor 5-HT3 de Serotonina , Agonistas do Receptor de Serotonina/farmacologia , Monoterpenos Bicíclicos , Linhagem Celular , Relação Dose-Resposta a Droga , Humanos , Imidazóis/farmacologia , Indóis/farmacologia , Monoterpenos/químicaRESUMO
NMDA-receptor-mediated mechanisms may be crucial in addictive states, e.g. alcoholism, and provide a target for the novel anti-craving compound acamprosate. Here, the pharmacological effects of acamprosate on NMDA-receptors were studied using electrophysiological techniques in different cell lines in vitro. Additionally, a possible modulation of brain NMDA-receptor subunit expression was examined in vivo in rats, and compared to two effective non-competitive NMDA-receptor antagonists, memantine and MK-801. Electrophysiology in cultured hippocampal neurons (IC(50) approx. 5.5mM) and Xenopus oocytes (NR1-1a/NR2A assemblies: IC(50) approx. 350 microM, NR1-1a/NR2B: IC(50) approx. 250 microM) consistently revealed only a weak antagonism of acamprosate on native or recombinant NMDA-receptors. In HEK-293 cells, acamprosate showed almost no effect on NR1-1a/NR2A or NR1-1a/NR2B recombinants (IC(50)s not calculated). Protein blotting demonstrated an up-regulation of NMDA-receptor subunits after acamprosate as well as after memantine or MK-801, in comparison to controls. After acamprosate, protein levels were increased in the cortex (NR1-3/1-4: 190+/-11% of controls) and hippocampus (NR1-1/1-2: 163+/-11%). The up-regulations observed after memantine (cortex, NR2B: 172+/-17%; hippocampus, NR1-1/1-2: 156+/-8%) or MK-801 (cortex, NR2B: 174+/-22%; hippocampus, NR1-1/1-2: 140+/-3%) were almost identical. No changes were detected in the brainstem. The present data indicate an extremely weak antagonism of NMDA-receptors by acamprosate. However, its ability to modulate the expression of NMDA-receptor subunits in specific brain regions - shared with the well established NMDA-antagonists memantine and MK-801 - may be of relevance for its therapeutic profile, especially considering the growing importance of NMDA-receptor plasticity in the research of ethanol addiction.
Assuntos
Dissuasores de Álcool/farmacologia , Encéfalo/efeitos dos fármacos , Antagonistas de Aminoácidos Excitatórios/farmacologia , Neurônios/efeitos dos fármacos , Receptores de N-Metil-D-Aspartato/efeitos dos fármacos , Taurina/farmacologia , Acamprosato , Animais , Encéfalo/metabolismo , Linhagem Celular , Maleato de Dizocilpina/farmacologia , Relação Dose-Resposta a Droga , Agonistas de Aminoácidos Excitatórios/farmacologia , Feminino , Humanos , Masculino , Memantina/farmacologia , N-Metilaspartato/farmacologia , Neurônios/metabolismo , Ratos , Ratos Wistar , Receptores de N-Metil-D-Aspartato/antagonistas & inibidores , Receptores de N-Metil-D-Aspartato/metabolismo , Taurina/análogos & derivados , XenopusRESUMO
Long-term depression (LTD) in the basolateral amygdala, following low frequency stimulation (1 Hz/900 pulses) of the lateral amygdala, was studied in an in vitro slice preparation of 2-3 weeks and 2-4 months old mice. Whole-cell patch-clamp recordings of neurons, visualized by means of infrared videomicroscopy, and extracellular field potential recordings were performed. Loading single neurons with the calcium chelator BAPTA (30 mM) did not reduce the excitatory postsynaptic currents following low frequency stimulation. However, buffering presynaptic calcium with BAPTA-AM, and application of the specific Ca2+/calmodulin-stimulated protein kinase II antagonist KN-62 (1-[N,O-bis(5-isoquinoline sulfonyl)-N-methyl-L-tyrosyl]-4-phenylpiperizine), blocked low frequency stimulation-induced LTD. The induction of LTD was reduced by the competitive N-methyl-D-aspartate receptor antagonist D-(-)-2-amino-5-phosphonopentanoic acid (50 microM), and blocked by the metabotropic glutamate receptor antagonist (-)-amino-4-carboxy-methyl-phenylacetic acid (1 mM), and by 5-hydroxytryptamine (5-HT; 30 microM) via the activation of 5-HT(1A) receptors. Also blocking GABA(A) receptor-mediated synaptic transmission with bicuculline (10 microM) or picrotoxin (20 microM) reduced the induction of LTD. Visually and electrophysiologically identified interneurons in slices from 2 weeks old mice, expressed in contrast to adult mice (2-4 months), pronounced LTD. Principal neurons showed only weak LTD after low frequency stimulation.A synopsis of these findings suggests a pivotal role of GABAergic interneurons and serotonergic afferents in the induction of LTD in the basolateral nucleus of the amygdala.
Assuntos
Tonsila do Cerebelo/fisiologia , Ácido Egtázico/análogos & derivados , Ácido Glutâmico/metabolismo , Interneurônios/fisiologia , Inibição Neural/fisiologia , Plasticidade Neuronal/fisiologia , Serotonina/metabolismo , Transmissão Sináptica/fisiologia , Ácido gama-Aminobutírico/metabolismo , Envelhecimento/efeitos dos fármacos , Envelhecimento/fisiologia , Tonsila do Cerebelo/citologia , Tonsila do Cerebelo/efeitos dos fármacos , Animais , Sinalização do Cálcio/efeitos dos fármacos , Sinalização do Cálcio/fisiologia , Proteína Quinase Tipo 2 Dependente de Cálcio-Calmodulina , Proteínas Quinases Dependentes de Cálcio-Calmodulina/antagonistas & inibidores , Proteínas Quinases Dependentes de Cálcio-Calmodulina/metabolismo , Quelantes/farmacologia , Ácido Egtázico/farmacologia , Estimulação Elétrica , Inibidores Enzimáticos/farmacologia , Antagonistas de Aminoácidos Excitatórios/farmacologia , Potenciais Pós-Sinápticos Excitadores/efeitos dos fármacos , Potenciais Pós-Sinápticos Excitadores/fisiologia , Antagonistas GABAérgicos/farmacologia , Interneurônios/citologia , Interneurônios/efeitos dos fármacos , Camundongos , Inibição Neural/efeitos dos fármacos , Plasticidade Neuronal/efeitos dos fármacos , Receptores de AMPA/antagonistas & inibidores , Receptores de AMPA/metabolismo , Receptores de N-Metil-D-Aspartato/antagonistas & inibidores , Receptores de N-Metil-D-Aspartato/metabolismo , Receptores de Serotonina/efeitos dos fármacos , Receptores de Serotonina/metabolismo , Serotonina/farmacologia , Antagonistas da Serotonina/farmacologia , Transmissão Sináptica/efeitos dos fármacosRESUMO
Laminins form a family of large multidomain glycoproteins of the extracellular matrix. The cellular distribution of laminin immunoreactivity in the adult mammalian central nervous system suggests an important role for laminins in mature brain function in addition to their role during brain development. To characterize the effects of this group of extracellular matrix molecules on mature brain function, intracellular recording techniques were applied to in vitro slice preparations of the rat neocortex. The experiments show that a peptide homologous to the C-terminal part of the gamma 1 chain of laminin modulates the electrical activity of pyramidal neurons in the adult neocortex of the rat. The peptide is part of the neurite outgrowth-promoting domain of the gamma 1 chain on the E8 fragment of laminin and it displays the neurite outgrowth-promoting activity of the native laminin molecule. Perfusion of in vitro brain slices with the peptide increased the input resistance of the neuronal membrane. In addition, a rise in inward rectification could be observed. These events were accompanied by a strong increase in direct excitability of the treated neurons. Immunohistochemistry techniques were applied to sections of the adult rat neocortex and hippocampus to demonstrate the presence of both the neurite outgrowth-promoting domain and the native laminin in the adult brain. An antiserum raised against the neurite outgrowth-promoting domain on the gamma 1 chain of laminin, which also recognized the free synthetic peptide, showed immunoreactivity on neurons. In addition, a population of glial fibrillary acidic protein-positive astrocytes in the hippocampus displayed immunoreactivity for this antibody. These results were confirmed by using several antibodies directed against the whole laminin-1 molecule. Neurons in the neocortex and hippocampus, as well as astrocytes in the hippocampus, demonstrated immunoreactivity for antibodies directed against the whole laminin-1 molecule. The results suggest that laminins containing the gamma 1 chain have the potential to modulate neuronal activity. This effect may be mediated either by direct cell-cell contact from surrounding cells, or through the neuronal expression of laminin or laminin-like molecules which are inserted into the neuronal cell membrane.