NO-Dependent mechanisms of amygdalofugal modulation of hypothalamic autonomic neurons

Neurophysiological and histochemical experiments on rats were performed to study the effects of the central nucleus of the amygdala on the activity of cells in various areas of the hypothalamus. Electrical stimulation of the medial part of the nucleus evoked marked excitatory reactions in neurons in the medial part of the paraventricular nucleus of the hypothalamus and the rostral part of the lateral hypothalamic area. Intravenous administration of N(G)-nitro-L-arginine methyl ester (L-NAME, 10 mg/kg) led to increases in evoked neuron responses. A series of histochemical studies following activation of the central nucleus demonstrated increases in the quantity and optical densities of NADP diaphorase (NADP-d)-positive neurons in the parvocellular zone of the paraventricular nucleus of the hypothalamus and the medial part of the lateral hypothalamic area. The activity of nitroergic cells in the ventrolateral part of the lateral hypothalamic area was suppressed in these conditions. These mechanisms may underlie the amygdalofugal modulation of the autonomic functions of the hypothalamus.