SEPTAL-LESIONS BLOCK SYMPATHETIC ACTIVATION FOLLOWING FRONTAL-CORTEX STIMULATION IN THE RAT

The rates of oxygen consumption, colonic and interscapular brown adipo se tissue temperature, and discharge of sympathetic nerves innervating the same tissue were recorded before and after orbital frontal cortex stimulation in three groups of rats. These groups consisted of animal s with electrolytic lesions of the nucleus medialis septi, with lesion s of nucleus lateralis septi or with sham lesions. The values of all t he variables considered were similar during the pre-stimulation time i n the three groups of rats. There was an increase in all the parameter s in sham-lesioned animals after electrical stimulation, while no chan ges were found in the two groups of injured rats. The results showed t hat the frontal cortex is involved in the control of thermogenesis thr ough the activation of the sympathetic nervous system. Medial and late ral septal nuclei, in spite of their neurochemical and pharmacological differences, share a common role in the pathway from the frontal cort ex to the hypothalamic area and the amygdala, which in turn drive the sympathetic nervous system.