RESUMO
c-fos immunoreactivity was used to map brain areas in which neurons reacted either to electrical stimulation or to microinjection of the excitatory amino acid kainate and of the GABAA antagonist, SR-95531, applied to the medial hypothalamus of freely moving rats. All these stimulations induced flight behavior of moderate intensity. Immunoreactive cells were found within a radius of 0.5 mm around the stimulated area. Distally, clusters of labeled cells were found ipsilaterally in the piriform and entorhinal cortices, in several amygdaloid nuclei, in the bed nucleus of the stria terminalis, in the septo-hypothalamic nucleus, in the paraventricular, anterior and dorsomedial hypothalamic nuclei, the the paraventricular thalamic nucleus, in the dorsal periaqueductal gray extending to the cuneiform nucleus, and bilaterally in the supramammillary decussation and the locus coeruleus. The specificity of the brain areas thus labeled was indicated by the unilateral pattern of activation as well as by the different pattern obtained after control microinjection of saline. Therefore, these results are likely to provide sound information about the brain structures involved in defensive-aversive behavior evoked from the medial hypothalamus.
Assuntos
Química Encefálica/efeitos dos fármacos , Química Encefálica/fisiologia , Hipotálamo Médio/efeitos dos fármacos , Hipotálamo Médio/fisiologia , Proteínas Proto-Oncogênicas c-fos/metabolismo , Animais , Comportamento Animal/efeitos dos fármacos , Comportamento Animal/fisiologia , Mapeamento Encefálico , Estimulação Elétrica , Antagonistas de Receptores de GABA-A , Hipotálamo Médio/citologia , Imuno-Histoquímica , Ácido Caínico/farmacologia , Masculino , Piridazinas/farmacologia , Ratos , Estimulação QuímicaRESUMO
The effects of bilateral infusions of GABA into the medial frontal cortex of the rat were studied in a delayed spatial alternation task. It was found that GABA (500 mM, 1 microliter/h during 7 days) impaired the performance of the rats in the previously learned task. Upon interruption of the treatment, the animals rapidly recovered normal performance scores. The results show that GABA infusions produce functional deficits similar to those produced by lesions of the frontal cortex. Moreover, the deficits are reversible upon interruption of the treatment. This technique may therefore be a useful tool for studying frontal lobe functions and the involvement of GABAergic mechanisms in cognitive processes.