Abstract

Information regarding the cardiovascular and subcutaneous microcirculatory response of Δ⁹-tetrahydrocannabinol (THC) was obtained by direct observation of the microcirculation in the bat wing, and by blood pressure, heart rate and body temperature recordings. An LD50 determination (535 mg/kg i.p.) indicated that doses of 100 and 200 mg/kg of THC would be well tolerated. These doses produced significant reduction in heart rate and rectal temperature within 30 minutes of THC administration. Blood pressure remained essentially unchanged until 85 minutes after injection. At this time, a significant reduction in blood pressure was obtained with the 200 mg/kg dose. No statistically significant response was noted in the subcutaneous small artery diameter (30-45 µ) after THC administration. However, small veins (60-90 µ) exhibited significant dilatation within 1 hour after the high dose of THC and remained dilated throughout the experimental period. Early effects on heart rate and rectal temperature indicate rapid i.p. absorption of THC. Latent effects on vein diameter and blood pressure may represent a cause/effect relationship.