[Paticipation of cannabinoid receptors in the regulation of cardiac rhythm and cardiac contractility].

It has been found that i. v. administration of cannabinoid receptor (CB) agonists (HU-210, ACPA, anandamide, methanandamide) induced a decrease in the heart rate (HR) in anesthetized rats. Pretreatment with CB1 receptor antagonist SR141716A completely abolished a negative chronotropic effect of CB receptor agonist HU-210. The CB2 receptor antagonist SRI 44528 did not prevent a HU-210-induced decrease in the HR. Pretreatment with the ganglion blocker hexamethonium had no effect on the negative chronotropic action of HU-210. Addition of HU-210 (100 nM) to perfusion solution induced a decrease in the HR, left ventricular development pressure, rate of contractility and relaxation of isolated perfused rate heart without change in end diastolic pressure. These data suggest that cardiac CBI receptor activation induces a decrease in the HR both in vivo and in vitro. An occupancy of the same receptors mediates a negative inotropic effects of cannabinoids.