Clonidine improves central attenuation of the baroreflex in spontaneously hypertensive rats.

To determine whether clonidine can improve the central alteration of the baroreflex in SHR, the centrally cut end of the aortic depressor nerve was electrically stimulated in SHR with intravenously administered clonidine. Aortic depressor nerve (ADN) stimulation elicited depressor and sympatho-inhibitory responses in a frequency-dependent manner in WKY and SHR. These responses were significantly smaller in SHR than in WKY. The attenuated depressor and sympatho-inhibitory responses to ADN stimulation in SHR were restored following i.v. injections of clonidine, although the drug did not affect the responses to ADN stimulations in WKY. These findings suggest that clonidine can improve central attenuation of the baroreflex in hypertension.