ABSTRACT
The nucleus of the solitary tract, commonly known as the nucleus tractus solitarius (NTS), is the primary relay station for the baroreceptor reflex arc. It contains abundant stores of endogenous catecholamines and serotonin because A2 and C2 cell groups and nerve endings, along with fibers from serotonergic Bl and B2 groups, are located within its immediate vicinity. Injections into the NTS of neurotoxins capable of selective neural destruction have also been used for assessing aminergic involvement in baroreflex regulation, but the chemical lesions thus produced have been used to study only catecholaminergic pathways. By showing that baroreflex responses were altered differently in 3- or 14-month-old rats by 6-hydroxydopamine, the results suggest that the baroreflex changes normally occurring with age may be due, at least in part, to modified catecholaminergic mechanisms in the NTS. Reflex tachycardia was reduced in both age groups, but reflex bradycardia was reduced only in 3-month-old and not in 14-month-old rats.
