Effects of chronic administration of delta9-tetrahydrocannabinol on the heart rate of mongrel dogs.

Chronic administration of delta9-tetrahydrocannabinol (delta9-THC) 1 mg/kg, s.c. twice a day for 7 days failed to produce any significant alterations in the peripheral autonomic transmission to the heart of mongrel dogs anesthetized with sodium pentobarbital. Prior to anesthesia, heart rate of the treated dogs was slightly greater than that of the placebo group. However, under pentobarbital anesthesia, heart rate of the delta9-THC treated animals was significantly lower than that of the placebo group. The data suggested that chronic delta9-THC may have an inhibitory effect on the central vagal structures and in addition, this agent antagonizes the ability of pentobarbital to elevate heart rate in dogs.