Clonidine microinjection into the mediocaudal region of the nucleus tractus solitarii (NTS) of the rat elicited dose-related (1.25–40.0 nmol) hypotension and bradycardia following NTS application. Cardiovascular effects produced by NTS injection of 5 nmol clonidine could be abolished by NTS pretreatment with the α2-adrenoceptor blocker, yohimbine (10 nmol). Dorsal medullary areas surrounding the NTS responded to clonidine microinjection with blood pressure falls similar to that seen after NTS microinjection. Bradycardic responses, however, were elicited more selectively from areas within anatomic boundaries of the NTS. These data suggest that, while blood pressure decreases can be demonstrated following direct application of clonidine into the medio-caudal NTS, the major interaction of clonidine with the NTS in the rat is to produce a decrease in heart rate.
ASJC Scopus subject areas
- Cellular and Molecular Neuroscience