EXPRESSION OF C-FOS PROTEIN IN THE NUCLEUS-TRACTUS-SOLITARIUS IN RESPONSE TO PHYSIOLOGICAL ACTIVATION OF CAROTID BARORECEPTORS

This study has utilized unilateral physiological pressure stimulation of a vascularly isolated carotid sinus combined with c-fos immunohisto chemistry to locate neurons of the nucleus tractus solitarius which ar e activated by carotid baroreceptors in the anesthetized, vagotomized dog. Carotid baroreceptor stimulation primarily activated neurons in t he ipsilateral commissural and medial subnuclei of the caudal nucleus tractus solitarius. In the intermediate and rostral nucleus tractus so litarius, carotid baroreceptor stimulation activated neurons in the do rsal and medial subnuclei. Results from this study also suggested that different subgroups of nucleus tractus solitarius neurons may be acti vated by baroreceptors with different pressure thresholds. The use of c-fos immunohistochemistry in this study has enabled the definition of populations of dorsal medullary neurons in the carotid baroreflex pat hway. The results also suggest a different projection of carotid baror eceptors with different pressure thresholds.