Central and peripheral sites for cardiovascular actions of dynorphin-(1-13) in rats.

Dynorphin-(1-13) (i.v.) induced bradycardia and hypotension in artificially ventilated anaesthetized rats. These effects were prevented by MRZ 2266 BS. The bradycardia was inhibited by bilateral vagotomy whereas the fall in blood pressure was not sensitive to bilateral vagotomy and chlorpheniramine treatment. In pithed rats, dynorphin-(1-13) reduced heart rate. This bradycardia was prevented by MRZ 2266 BS but not by tertatolol and cimetidine. It is suggested that the dynorphin-(1-13)-induced effects result from the stimulation of central and cardiac kappa-opiate receptors.