Aortic baroreceptor reflex pathway: a functional mapping using [3H]2-deoxyglucose autoradiography in the rat

The organization of pathways within the central nervous system which are activated by aortic baroreceptor input was studied in the urethane anesthetized rat using the 2-deoxyglucose method. [3H]2-deoxyglucose was administered i.v. while either the aortic nerve was electrically stimulated or aortic baroreceptors were physiologically activated by pulse increases in arterial pressure in animals with bilateral denervation of the carotid sinus. Autoradiographs of transverse sections of the central nervous system were developed and analyzed for changes in metabolic activity in discrete regions compared to control animals, as indicated by the density of the photographic emulsion. Electrical stimulation of the aortic nerve resulted in all animals in an increase in the uptake of deoxyglucose in a number of sites throughout the central nervous system, primarily ipsilateral to the site of stimulation. In the brainstem, structures previously implicated in cardiovascular reflexes were labeled. These included the nucleus of the solitary tract, the solitary tract, the dorsal motor nucleus of the vagus, and the nucleus ambiguus. In addition, the inferior olivary nucleus, the parabrachial nuclei and the ventrolateral reticular formation showed increased labeling. In the hypothalamus, increased labeling was observed only in the paraventricular and supraoptic nuclei.