Distribution of catecholamines and serotonin in 17 portions of rat ventromedial nucleus and effect of acute immobilization stress.

The distribution of catecholamines (i.e. adrenalin -- A, noradrenalin -- NA, dopamine -- DA) and serotonin (5-HT) in 17 portions of hypothalamic ventromedial nucleus (VMN) and the effect of acute immobilization stress on their levels were studied in rats using of a special dissection technique and a sensitive radioenzymatic microassay. In unstressed rats distinct differences of biogenic amine concentrations between individual portions within the hypothalamic ventromedial nucleus subdivisions were found. The concentration of all catecholamines investigated, i.e. NA, A and DA was lower in the lateral half of VMN, while in the distribution of 5-HT we did not find such apparent regional differences. After acute immobilization stress for 30 min significant changes in all measured neurotransmitters, in NA and A decreases and in DA and 5-HT increases, were detected in several subdivisions of the nucleus. On the basis of the present data we suppose that not all subdivisions of the VMN are equally engaged in neuroendocrine processes activated during acute stress.