Effects of acute administration of delta9-tetrahydrocannabinol on pulmonary hemodynamics of anesthetized dogs.

I.v. administration of delta9-THC (2.5 mg/kg) To anesthetized dogs resulted in a decrease in heart rate, pulmonary blood flow (PBF), and a significant increase in pulmonary artery pressure (PAP) and total pulmonary vascular resistance (PVR). The increase in PVR to delta9-THC was significantly reduced by cardiac pacing, and was virtually abolished either by bilateral vagotomy or by pretreatment with hexamethonium. The data indicated the delta9-THC induced elevation of PVR was mediated via reflexogenic mechanisms involving afferent vagi and efferent autonomic pathways.