Investigating the role of Prefrontal Neurons in cognitive tasks through Fiber Photometry and Adapted Barnes Maze Protocols

The medial prefrontal cortex (mPFC) is essential in the execution of cognitive tasks, however very little is known on how these neurons are modulated during specific tasks and which subtype of neurons are responsible for so. Therego, with the intention of addressing this issue, we recorded mPFC gabaergic and glutamatergic activation patterns through fiber photometry (FIP) in mice, while simultaneously performing the Barnes Maze (BM) cognitive task (4 day behavioral trial). In addition, an altered structural and procedural protocol for BM was validated in this study due to necessary modifications allowing FIP and BM to happen simultaneously. A successful protocol validation was followed by our preliminary results, which showed that both glutamatergic and gabaergic neurons presented significant change in activation intensity and number of events in specific contexts throughout the task days. In addition, when stratified and crossed with BM performance parameters, such as latency to complete tasks and adopted strategy, glutamatergic and gabaergic neurons presented a significant decline in both activation patterns and number of activation events throughout the days. This data suggest not only an important role of glutamatergic and gabaergic mPFC neurons in learning, memory and decision making, but also that activation patterns of each of these groups may serve as markers for cognitive progression and/or dysfunction. KEY-WORDS: Memory, Learning, Decision Making, Medial Prefrontal Cortex (mPFC), Fiber Photometry (FIP), Barnes Maze (BM), Glutamatergic, Gabaergic, Neuronal Activity, Neuronal Activation Patterns, Neuronal Dynamics.

O córtex pré-frontal medial (mPFC) é essencial na execução de tarefas cognitivas, no entanto, pouco se sabe sobre como esses neurônios são modulados durante tarefas específicas e qual subtipo de neurônios é responsável por isso. Portanto, com a intenção de abordar essa questão, registramos os padrões de ativação de neurônios gabaérgicos e glutamatérgicos do mPFC por meio de fotometria de fibra (FIP) em camundongos, enquanto realizávamos simultaneamente a tarefa cognitiva do Labirinto de Barnes (BM) (ensaio comportamental de 4 dias). Além disso, um protocolo estrutural e procedimental alterado para o BM foi validado neste estudo devido a modificações necessárias que permitiram a realização simultânea de FIP e BM. Uma validação bem-sucedida do protocolo foi seguida pelos nossos resultados preliminares, que mostraram que tanto os neurônios glutamatérgicos quanto os gabaérgicos apresentaram mudanças significativas na intensidade de ativação e no número de eventos em contextos específicos ao longo dos dias da tarefa. Além disso, quando estratificados e cruzados com parâmetros de desempenho do BM, como latência para completar as tarefas e estratégia adotada, os neurônios glutamatérgicos e gabaérgicos apresentaram uma diminuição significativa nos padrões de ativação e no número de eventos de ativação ao longo dos dias. Esses dados sugerem não apenas um papel importante dos neurônios glutamatérgicos e gabaérgicos do mPFC na aprendizagem, memória e tomada de decisões, mas também que os padrões de ativação de cada um desses grupos podem servir como marcadores de progressão e/ou disfunção cognitiva. PALAVRAS-CHAVE: Memória, Aprendizagem, Tomada de Decisões, Córtex Pré-Frontal Medial (mPFC), Fotometria de Fibra (FIP), Labirinto de Barnes (BM), Glutamatérgico, Gabaérgico, Atividade Neuronal, Padrões de Ativação Neuronal, Dinâmica Neuronal.

Efficacy of gabapentin in the improvement of pruritus and quality of life of patients with notalgia paresthetica

BACKGROUND: notalgia paresthetica is a subdiagnosed sensory neuropathy presenting as a condition of intense itching and hyperchromic macule on the back that interferes with daily habits. OBJECTIVES: To determine the efficacy of treatment of notalgia paresthetica using oral gabapentin, assessing the degree of improvement in itching and influence on quality of life. Moreover, to evaluate the signs and symptoms associated with notalgia paresthetica. METHODS: We conducted an experimental, non-randomized, parallel, non-blinded study including 20 patients with clinical and histopathological diagnosis of notalgia paresthetica. After application of the visual analogue scale of pain adapted for pruritus and of the questionnaire of dermatology life quality index (DLQI), ten patients with visual analogue scale > 5 were given treatment with gabapentin at the dose of 300 mg/day for four weeks. The other ten were treated with topical capsaicin 0.025% daily for four weeks. After the treatment period, patients answered again the scale of itching. RESULTS: The use of gabapentin was responsible for a significant improvement in pruritus (p=0.0020). Besides itching and hyperchromic stain on the back, patients reported paresthesia and back pain. It was observed that the main factor in the worsening of the rash is heat. CONCLUSION: Gabapentin is a good option for the treatment of severe itching caused by nostalgia paresthetica. .

Sedative and anesthetic activities of the essential oils of Hyptis mutabilis (Rich.) Briq. and their isolated components in silver catfish (Rhamdia quelen)

This study evaluated the sedative and anesthetic effects of the essential oils (EO) of Hyptis mutabilis (Rich.) Briq. and their isolated components on silver catfish (Rhamdia quelen). Quantitative chemical differences between the EOs obtained from leaves and inflorescences were verified, and a new chemotype rich in globulol was described. Although there were no significant differences in the time of induction for sedation and anesthesia between the EOs, only the leaf EO at 344 mg/L anesthetized all fish without side effects. Fractionation of the leaf EO was carried out by column chromatography. The isolated compounds [(+)-1-terpinen-4-ol and (-)-globulol] showed different activity from that detected for the leaf EO in proportional concentrations and similar sedation to a eugenol control at 10 mg/L. However, fish exposed to 1-terpinen-4-ol (3 and 10 mg/L) did not remain sedated for 30 min. Anesthesia was obtained with 83-190 mg/L globulol, but animals showed loss of mucus during induction and mortality at these concentrations. Synergism of the depressor effects was detected with the association of globulol and benzodiazepine (BDZ), compared with either drug alone. Fish exposed to BDZ or globulol+BDZ association showed faster recovery from anesthesia in water containing flumazenil, but the same did not occur with globulol. In conclusion, the use of globulol in aquaculture procedures should be considered only at sedative concentrations of 10 and 20 mg/L, and its mechanism of action seems not to involve the GABAA-BDZ system.

GABA-induced inactivation of Cebus apella V2 neurons: effects on orientation tuning and direction selectivity

We investigated the GABA-induced inactivation of V2 neurons and terminals on the receptive field properties of this area in an anesthetized and paralyzed Cebus apella monkey. Extracellular single-unit activity was recorded using tungsten microelectrodes in a monkey before and after pressure-injection of a 0.25 or 0.5 M GABA solution. The visual stimulus consisted of a bar moving in 8 possible directions. In total, 24 V2 neurons were studied before and after blocker injections in 4 experimental sessions following GABA injection into area V2. A group of 10 neurons were studied over a short period. An additional 6 neurons were investigated over a long period after the GABA injection. A third group of 8 neurons were studied over a very long period. Overall, these 24 neurons displayed an early (1-20 min) significant general decrease in excitability with concomitant changes in orientation or direction selectivity. GABA inactivation in area V2 produced robust inhibition in 80% and a significant change in directional selectivity in 60% of the neurons examined. These GABA projections are capable of modulating not only levels of spontaneous and driven activity of V2 neurons but also receptive field properties such as direction selectivity.

Gabaergic mechanisms of anterior and ventromedial hypothalamic nuclei in the expression of freezing in response to a light-conditioned stimulus

The amygdala, dorsal periaqueductal gray (dPAG), and medial hypothalamus have long been recognized to comprise a neural system responsible for the generation and elaboration of unconditioned fear in the brain. This neural substrate is well known to be under tonic inhibitory control exerted by ã-aminobutyric acid (GABA) mechanisms. Some evidence also suggests that these structures integrate conditioned fear. A recent study using the fear-potentiated startle paradigm showed that GABAergic mechanisms in the anterior hypothalamic nucleus (AHN) and dorsomedial part of the ventromedial hypothalamic nucleus (VMHDM) regulate conditioned fear. The present study examined the extent to which GABAergic mechanisms in these brain regions are involved in conditioned fear by measuring freezing in response to a light used as a conditioned stimulus (CS). The GABA A receptor agonist muscimol and the GABA-synthesizing enzyme glutamic acid decarboxylase inhibitor semicarbazide were used as an enhancer and inhibitor of GABA mechanisms, respectively. Muscimol and semicarbazide were injected into the AHN or VMHDM of rats before fear conditioning. Muscimol injections into the AHN and VMHDM significantly reduced conditioned freezing, whereas inhibition of GABA transmission increased this conditioned response in the AHN. The present study further supports the hypothesis that GABAergic mechanisms in the AHN and VMHDM exert inhibitory control on the neural substrates of conditioned fear in the hypothalamus.

Avances en las bases moleculares de la anestesiología / Advances in the molecular basis of anaesthesiology

Aunque la primera anestesia se dio hace más de 100 años, el posterior surgimiento de múltiples anestésicos permitió desarrollar todos los componentes implicados durante su administración. Solo hasta hace aproximadamente 30 años se han venido conociendo las bases moleculares de los mecanismos de acción de los anestésicos gracias a la biología molecular, con un vertiginoso desarrollo en los últimos 10 años. Es de vital importancia para el anestesiólogo conocer las bases moleculares de la anestesia, lo cual le permitirá entender efectos, interacciones y toxicidad de los anestésicos e impactará en la adecuada administración de los medicamentos disponibles, a la vez que influirá en el desarrollo de nuevos fármacos con acciones más específicas.

Although the first anaesthetic was given more than a century ago, the subsequent emergence of several anaesthetic drugs enabled several components involved in its administration to be identified. Only during the past 30 years has the molecular basis for anaesthetics’ mechanisms of action become known (especially undergoing vertiginous progress during the last decade). It is of vital importance for an anaesthesiologist to know the molecular basis of anaesthesia and ensure complete comprehension of anaesthetics’ effects, interactions and toxicity. Such knowledge will have an impact on the suitable administration of available drugs and the creation of new ones having more specific action.

Involvement of GABAergic mechanisms of the dorsal periaqueductal gray and inferior colliculus on unconditioned fear

The fact that the dorsal periaqueductal gray (dPAG) and inferior colliculus (IC), together with superior colliculus, medial hypothalamus and amygdala, constitute the brain aversion system has been well-established. Stepwise increases in the intensity of electrical stimulation of dPAG or IC cause freezing and escape responses, which are followed by a freezing behavior that lasts after the interruption of the stimulation. Freezing and escape are unconditioned defensive behaviors derived from the stimulation of the output centers for the defense reaction, whereas the post-stimulation freezing is the behavioral counterpart of the processing of aversive information. Although GABA-A mechanisms of the midbrain tectum exert a tonic inhibitory influence on the neural substrates of unconditioned fear, their influence on the processing of aversive information is not completely understood. Thus, the present study examines the effects of injections of the GABA-A receptor agonist muscimol (1 and 2 nmol/0.2 µL) or the glutamic acid decarboxylase blocker semicarbazide (5 and 7.5 µg/0.2 µL) into dPAG or IC of Wistar rats on freezing and escape thresholds determined by electrical stimulation of these same structures and on post-stimulation freezing. Intra-dPAG injections of muscimol increased and semicarbazide decreased the freezing and escape thresholds of electrical stimulation of the dPAG. Only semicarbazide enhanced the dPAG post-stimulation freezing. Intra-IC injections of muscimol significantly increased aversive thresholds, while having no effect on IC post-stimulation freezing. Intra-IC injections of semicarbazide had no significant effects. These findings suggest that GABAergic mechanisms are important regulators of the expression of unconditioned fear in dPAG and IC, whereas only in dPAG GABA appears to play a role on the sensory gating towards aversive information during post-stimulation freezing.

Hipótesis epigenética de la esquizofrenia: bases moleculares y modelos experimentales / Epigenetic Hypothesis for Schizophrenia: Molecular bases and Experimental Models

Si bien la predisposición a desarrollar esquizofrenia ha sido, en parte, atribuida a un componente genético, la evidencia experimental de los últimos años sugiere que este trastorno puede ser el resultado de una aberración epigenética. De ahí que a las hipótesis hiperdopaminérgica e hipoglutamatérgica, se le sume la hipótesis epigenética de la esquizofrenia. Esta última propone que la fisiopatología de la enfermedad se sostiene en cambios en la expresión génica por una estructura aberrante de la cromatina, más que por cambios en la secuencia del ADN. De los múltiples blancos moleculares propuestos en la etiología de la enfermedad, cobra particular importancia la enzima ácido glutámico descarboxilasa, encargada de sintetizar el ácido γ - amino butírico (GABA), en especial la isoforma de 67 kDa, y la reelina, cuyos genes codificantes parecen estar hipermetilados en pacientes con esquizofrenia cuando se los compara con individuos sanos. Esto determina un menor nivel de expresión de la enzima y niveles disminuidos de GABA, lo que involucra íntimamente a este neurotransmisor en el desarrollo de la esquizofrenia.

Although the tendency to develop shizophrenia has partly been ascribed to a genetic component, experimental evidence gathered in recent years suggests that this disorder may be the producto of an epigenetic aberration. Hence, the hyperdopaminergic and hupoglutamatergic hypotheses add on the epigenetic hypothesis for shizophrenial. The latter proposes that the physiopathology of schizophrenia stems from changes in the gene expression, into an aberrant structure of the chromatin, rather than from DNA sequence variations. Oif the multiple molecular targets proposed in the etiology of shizophrenia, one which acquires particular significance is the enzyme, glutamic acid decarboxylase, which synthesizes Y-aminobutyric acid (GABA), especially 67-kDa isoform and reelin, whose codifying genes seem to be hypermethylated in patients with schizophrenia, as compared with healthy individuals. This determines a lower level of expression of the enzyme, as well as rduced GABA levels, which evidences the close relationship betweeen this neurotransmissor and the development of schizophrenia.

Alteraciones de la Corteza Prefrontal en la esquizofrenia (Tercera parte) / Alterations in the Prefrontal Cortex in Schizophrenia (Third Part)

La Corteza Prefrontal (CPF) y específicamente la Corteza Prefrontal Dorso Lateral es una corteza de asociación heteromodal, particular y selectivamente alterada en la esquizofrenia. La CPFDL (Corteza Prefrontal Dorso Lateral) presenta disminución selectiva de su conectividad sináptica, con disminución del neuropilo y del tamaño de los somas neuronales, con aumento de la densidad neuronal. Hay disminución de las aferencias provenientes del ATV (área tegmental ventral) en las capas medias y de las provenientes del NDM (núcleo dorso medial) del Tálamo en las medias y profundas, con disminución del volumen del mismo. Las alteraciones se agravan con el podado fisiológico en la adolescencia, produciendo fallas en los circuitos córtico-talámicos, córtico-estrio-tálamo-corticales y córtico-tálamo-cerebelares, con fallas en la regulación del filtro talámico y estados de hiperdopaminergia subcortical secundaria, relacionados con los síntomas positivos de la enfermedad. Esta revisión será presentada en tres partes. En la primera y segunda parte del trabajo se desarrollaron las alteraciones cognitivas descriptas en la esquizofrenia, específicamente la Memoria de Trabajo y la circuitería de la Corteza Prefrontal. En la tercera parte se tratará la importancia de la neurotransmisión dopaminérgica y neurofisiopatología de la CPF en la esquizofrenia.

The Prefrontal Cortex (PFC), and specifically, the Dorsolateral Prefrontal Cortex is a heteromodal association cortex, which is particularly and selectively altered in schizophrenia. The DLPC (Dorsolateral Prefrontal Cortex) displays a selective decrease of its synaptic connectivity, with a reduction of the neuropile as well as the size of neural somas, with an increased neural density. There is a decrease in the afferents of the ventral tegmental area (VTA), in the medium layers and the layers of the MDN (medial dorsal nucleus) of the Thalamus, in the medium and deep layers, with a reduction of its volume. Alterations become worse with physiological crop in adolescence, leading to impairments of the corticothalamic, cortico-striatal-thalamic-cortical and cortico-thalamic-cerebellar circuits, with impairments in the regulation of the thalamic filter, and states of secondary subcortical hyperdopaminergia, associated with the pisitive symptoms of the disease. This review will be divided in three parts. The first and the second part consist in the cognitive alterations described in schizophrenia, specifically, the Working Memory as well as the Prefrontal Cortex circuitry. The Third part deals with the importance of dopaminergic neurotransmission and the neurophysiopathology of the PFC in schizophrenia.

Role of the caudal pressor area in the regulation of sympathetic vasomotor tone

It is well known that the ventrolateral medulla contains neurons involved in the tonic and reflex control of the cardiovascular system. Two regions within the ventrolateral medulla were initially identified: the rostral ventrolateral medulla (RVLM) and the caudal ventrolateral medulla (CVLM). Activation of the RVLM raises arterial blood pressure and sympathetic nerve activity, and activation of the CVLM causes opposite effects. The RVLM premotor neurons project directly to sympathetic preganglionic neurons and are involved in the maintenance of resting sympathetic vasomotor tone. A significant proportion of tonic activity in the RVLM sympathetic premotor neurons is driven by neurons located in a third region of the ventrolateral medulla denominated caudal pressor area (CPA). The CPA is a pressor region located at the extreme caudal part of the ventrolateral medulla that appears to have an important role controlling the activity of RVLM neurons. In this brief review, we will address the importance of the ventrolateral medulla neurons for the generation of resting sympathetic tone related to arterial blood pressure control focusing on two regions, the RVLM and the CPA.

Efeitos dos triterpenos a- e ß-amirina e de seus derivados acetilados no sistema nervoso central [manuscrito] / Effects of a- and ß-amyrin triterpenes and its acetylated derivatives in the central nervous system [manuscript]

A mistura triterpênica de α- e β-amirina (AMI) é obtida da planta Protium heptaphyllum Aubl March (Família Burseraceae), comum em vários estados brasileiros e conhecida popularmente como breu branco, também é utilizada na prática da medicina popular para tratar várias enfermidades. O acetato de α- e β-amirina (AcAMI) é a forma acetilada desta mistura triterpênica. Vários estudos experimentais já foram feitos utilizando estes triterpenos, mas estudos da ação destes no Sistema Nervoso Central (SNC) ainda são escassos. O objetivo deste trabalho foi avaliar o efeito da administração destes compostos naturais em camundongos e verificar uma possível atividade sedativa, ansiolítica, antidepressiva e anticonvulsivante, procurando ainda esclarecer por que mecanismos estes compostos agem. A metodologia utilizada foi utilizando testes farmacológicos já descritos na literatura e estudos de doseamento de monoaminas e aminoácidos através de HPLC. Os resultados mostraram que tanto a AMI como o AcAMI mostraram-se bastante ativos farmacologicamente. No teste da Campo Aberto ambas misturas (AMI e AcAMI) administradas por via aguda e sub-crônica demonstraram efeitos sedativos, nas doses de 10, 25 50 mg/kg, após a constatação da diminuição do movimento exploratório dos animais e do número de grooming e de rearing, utilizando o diazepam como controle positivo. No Teste do Plus Maze também ambas as misturas demonstraram atividade ansiolítica aumentando o número de entradas e o tempo de permanência nos braços abertos...

Monitorização dos níveis de consciência em anestesiologia / Consciousness level monitorization in anesthesia

A anestesia geral é o conjunto de vários estados fisiológicos, incluindo o estado de inconsciência. O receptor do ácido gama-aminobutírico, subtipo A, tem se revelado importante alvo de drogas anestésicas, na medida em que contribuiu para indução de sedação e inconsciência. O anestesiologista deve ter conhecimento dos mecanismos de ação dos fármacos na transmissão do sistema gabaérgico e saber utilizar os meios disponíveis para monitorizar a consciência do paciente anestesiado. Nesse contexto, os aparelhos que processam os sinais do eletroencefalograma têm se mostrado muito úteis na motorização da inconsciência.

Transtorno bipolar: tratando o episódio agudo e planejando a manutenção / Bipolar disorder: treating the acute episode and planning the maintenance

O transtorno bipolar do humor é considerado uma condição psiquiátrica grave e recorrente, tendo várias vezes um curso crônico e incapacitante. Levando-se em consideração sua natureza episódica, ao tratar o episódio agudo devemos sempre planejar a terapêutica de manutenção. Este artigo apresenta o caso de uma paciente com uma forma grave de transtorno bipolar, com uma longa história de doença, no momento hospitalizada por um episódio maníaco com sintomas disfóricos. A discussão que se segue é realizada no modelo de uma conferência clínica, com o comentário de dois experts na área, abordando vários aspectos relacionados a diagnóstico, evolução e tratamento do caso.

Avaliação da eficácia e tolerabilidade da vigabatrina na síndrome de West / Efficacy and tolerability of vigabatrin in West syndrome

A síndrome de West (SW) é uma epilepsia grave específica da infância, que se caracteriza pela tríade: espasmos em salvas, deterioração ou atraso neuropsicomotor e hipsarritmia ao eletrencefalograma. OBJETIVO: Avaliar a eficácia e segurança da vigabatrina (VGB) no tratamento da SW. MÉTODO: Foram sujeitos do estudo todos os pacientes com diagnóstico estabelecido de SW, que freqüentam ou freqüentaram o Ambulatório de Epilepsia Infantil do Hospital das Clínicas da UNICAMP, usam ou usaram VGB na tentativa de controlar as crises. Avaliamos sexo, idade, etiologia (sintomática ou criptogênica), doença(s) associada(s), idade do início dos espasmos, freqüência das crises antes e após o uso de VGB, achados de neuroimagem, EEG antes e depois do uso de VGB, medicações associadas, tempo para controle das crises, eletroretinograma, queixa visual após uso de VGB, efeitos adversos e história familial de epilepsia. RESULTADOS: Foram avaliados 23 pacientes, sendo 16 do sexo masculino. A idade variou entre 1ano e 3 meses a 11 anos e 5meses (média = 5anos e 3meses). Dezesseis (69,5 por cento) pacientes apresentaram controle completo das crises, 5 (22 por cento) tiveram controle parcial e em 2 (8,5 por cento) pacientes os espasmos não foram controlados. Apenas uma paciente teve retinopatia gabaérgica. Seis pacientes (26 por cento) apresentaram eventos adversos - sonolência, agressividade ou retinopatia. Os pacientes com o início da SW após 6 meses de idade apresentaram melhor resposta à VGB (p<0,05). Não houve diferença na resposta ao tratamento quanto ao tempo de introdução da VGB ou à etiologia (p>0,05). Após o tratamento com VGB, nenhum EEG apresentou hipsarritmia e 50 por cento normalizaram. CONCLUSÃO: Apesar do risco de retinopatia gabaérgica, os resultados acima mostram que o uso da VGB no controle dos espasmos infantis se justifica em pacientes com SW.

Inhibition of L-glutamate and GABA synaptosome uptake by crotoxin, the major neurotoxin from Crotalus durissus terrificus venom

This paper describes a brief study on the crotoxin mechanism of action, regarding the transport of GABA and L-glutamate in rats cortico-cerebral synaptosomes and in heterologous systems, such as COS-7 cells expressing gabaergic transporters, and C6 glioma cells and Xenopus oocytes expressing glutamatergic transporters. Crotoxin concentrations over 1 µM caused an inhibitory effect of ³H-L-glutamate and ³H-GABA, and reversibly inhibited L-glutamate uptake by C6 glioma cells. When COS-7 cells were assayed, no inhibition of the ³H-GABA transport could be evidenced. Crotoxin kept its inhibitory effect on neurotransmitters uptake even when Ca2+ ions were removed from the medium, therefore, independently of its PLA2 activity. In addition, high concentrations (2 mM) of BPB did not avoid the action of crotoxin on the neurotransmitters uptake. Crotoxin also inhibited ³H-L-glutamate, independently on Na+ channel blockade by TTX. In addition, an evaluation of the lactic dehydrogenase activity indicated that uptake inhibition does not involve a hydrolytic action of crotoxin upon the membrane. We may also suggest that crotoxin acts, at least partially, altering the electrogenic equilibrium, as evidenced by confocal microscopy, when a fluorescent probe was used to verify cell permeability on C6 glioma cells in presence of crotoxin.

Efecto de la activacion gabaergica sobre la maduracion sexual en ratas hembras peripuberales / Effect prologed gabaergic activation on the pubertal development of female rats

Evaluamos 1) efecto del tratamiento prolongado (días 23-29 postnatales) con ácido aminooxiacético (AAOA) sobre el desarrollo puberal en ratas hembra; este tratamiento aumentó el contenido de GABA (p< 0.002), disminuyendo el de GnRH y glutamato (p < 0.05 y < 0.02) en hipotálamo. La LH (p < 0.05) y el estradiol (p < 0.005) séricos cayeron. La apertura vaginal fue a los 30.8 + 0.6 días en los controles, y a los 36.7 + 0.98 días en las tratadas (p < 0.0001). 2) A los 30 días, el tratamiento agudo con AAOA redujo la liberación ex vivo de GnRH y de glutamato la de taurina. Este efecto fue similar al observado agregando al medio agonistas GABA-A y B. Conclusiones: la activación peripuberal del sistema GABAérgico frena el eje reprodutor, produciendo un retraso en el desarrollo. Esto podría atribuirse a la existencia, en esta etapa, de interrelaciones fisiológicas entre los aminoácidos que regulan la secreción de GnRH (GABA, glutamato, taurina).

Inhibitory effects of Diazepam in rat Vas Deferens: role of Calcium

Diazepam and Ro5-4864 effects on noradrenaline-induced rat vas deferend contractions were studied. We investigated whether central or peripheral type benzodiazepine receptors were involved, by studying the effects of the selective central or peripheral benzodiazepine receptor antagonists, flumazenil (Ro 151788) or PK 11195 respectively. Diazepam interactions with GABA, adenosine, theophylline, and hypercalcic medium (3.5mM) were studied. Also, we investigate diazepam effect on KC1 depolarized vas deferens. Results showed that diazepam (10(-4) to 1.7x10(-4) M)) and Ro 5-4864 (10(-5) to 5.5x10(-5)M) inhibited NA-induced vas deferens contractions and that neither flumazenil nor PK 11195 antagonized diazepam or Ro 5-4864 inhibitory effects respectively. GABA, adenosine and theophylline did not modify neither NA vas deferens response nor diazepam inhibitory action. Diazepam effect was significantly reduced in an 3.5 mM calcium medium and KC1 vas deferense was inhibited by diazepam 1.3x10(-5) and 1.3 x 10(-4) M. It is concluded that in rat vas deferens diazepam effect seems to be related with calcium mobilization.

Effect of manipulation of the GABA system on dopamine-related behaviors

The interaction between GABAergic and dopaminergic system within the central nervous system was investigated in rats using the open-field apparatus and apomorphine-induced stereotypy, and in mice using haloperidol-induced catalepsy. The single intraperitoneal adminsitration of baclofen 3.0 mg/kg, 4,5,6,7-tetrahydroisoxasolo-(5,4-c) piridin-3-ol (THIP) 10.0 mg/kg and picrotoxin 2.0 mg/kg decreased both ambulation and rearing frequencies of the rats in the open-field; only the GABA agonists increased the duration of animal immobility. THIP (10.0 mg/kg) increased the duration of haloperidol-induced catalepsy. For apomorphine-induced stereotypy, baclofen 3.0 mg/kg and picrotoxin 1.0 mg/kg induced a significant leftward displacement of the control dose-response curve constructed for apomorphine (0.1-10 mg/kg) in relation to the control. In addition, baclofen, THIP, picrotoxin and 3-mercaptopropionic acid (3-MPA) 10.0 mg/kg decreased both rearing and sniffing behaviors elicited by apomorphine and increased licking and/ or gnawing. Different mechanisms seem to be involved in the similar effects induced by GABA agonists and antagonists. Picrotoxin induced stereotyped movements per se with a dose-dependent effect, but baclofen and THIP did not. The present data suggest that GABA manipulation facilitates the progressive activation of the different dopaminergic pathways involved in stereotyped behaviors, thus increasing those stereotyped components (gnawing and licking) that appear after a high level of activation of dopaminergic pathways