Male rats were implanted subcutaneously with a pellet containg 75 milligrams of morphine base or placebo, and naloxone hydrochloride (4 milligrams per kilogram of body weight) was administered 72 hours later. Treatment with delta-9-tetrahydrocannabinol (2, 5, or 10 milligrams per kilogram) 1 hour before maloxone administration significantly reduced the intensity of abstinence; the two higher doses blocked the appearance of wet shakes and escapes, diarrhea, and increased defecation. delta-9-Tetrahydrocannabinol did not induce abstinence itself, and prior treatment with cannabidiol was ineffective in reducing naloxoneprecipitated abstinence in animals with morphine pellets. These data suggest that delta-9-tetrahydrocannabinol may be of value in facilitating narcotic detoxification.

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Acute and chronic effects of △⁸-THC on tail-flick, heart rate, and rectal temperature responses in conscious, unrestrained male rats were studied. In the acute experiment unidirectional, dose-dependent analgesic, hypothermic, and negative chronotropic cardiac effects were observed within the dose range employed. Of the three variables, heart-rate decreases were most sensitive to the effects of THC, reaching significance at 2 mg/kg. Rapid development of tolerance occurred for all three measures, with complete tolerance developing within 13 days only to the heart-rate decreases. The results are discussed in the context of previous data.

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