CARDIOVASCULAR EFFECTS OF CENTRALLY ACTIVE CHOLINOMIMETICS IN CONSCIOUS AND ANESTHETIZED RATS - THE ROLE OF AMYGDALA

Central cardiovascular effects of cholinergic agonists depend on the d ose, site and mode of administration, species, and to the state of the animal. Intravenous injection of physostigmine and intracerebroventri cular injection of carbachol produced presser and tachycardic response s in urethane-anesthetized rats. Both agents also elicited presser res ponses in conscious rats, but bradycardia occurred in the presence of anesthesia, Additionally, presser responses to physostigmine, but not to carbachol, were significantly exaggerated by urethane anesthesia. T hese results demonstrate that anesthesia depresses cardiovascular refl exes and the inhibitory control mechanisms on acetylcholine release fr om the nerve endings involved in cardiovascular regulation. The role o f the central nucleus of the amygdala (CNA) was also investigated in t his study. The presser effects of intracerebroventricular injection of carbachol were significantly attenuated by electrolytic ablation of t he CNA, but heart rate changes were not altered both in anesthetized a nd conscious rats. These results indicate that the CNA plays a role in cholinergic control of blood pressure, but not in the regulation of h eart rate.