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At least 37 records · Page 2Linked to original sources
PubMed1979

Dose and physical dependence as factors in the self-administration of morphine by rats.

Groups of naive rats were offered morphine sulfate for self-admininstration in doses of 0.0032-10 mg/kg for 6 days. On day 7 saline was substituted for morphine. Loss of weight was taken as physiological evidence of dependence. Rats that did not lose weight formed a single population whose mean injection rate did not differ from control rats receiving only saline injections. Injection rates for rats losing weight were log-normally distributed, and the mean of the logarithms of the injection rates was linearly related to the logarithm of the dose. Mean daily injection rates averaged 12 for controls, 23 at 10 mg/kg, and 411 at 0.01 mg/kg. A transient increase in morphine intake after an injection of nalorphine was taken as behavioral evidence of dependence. Nalorphine increased morphine intake when rats were self-injecting 0.32 and 1.0 mg/kg of morphine, but not 0.032 or 0.1 mg/kg. The reinforcing property of morphine may occur without behavioral evidence of dependence.

Animals↗
PubMed1979

Self-administration of delta 9-tetrahydrocannabinol by rats.

The present study examines the dose-response pattern of delta 9-tetrahydrocannabinol self-injection in naive rats at 80% reduced body weight and 100% body weight, both conditions with a fixed-time 1 min (FT-1) food delivery schedule. The results indicated that food deprived animals tested on a FT-1 min schedule self-injected low doses of delta 9-THC at a higher rate than those animals at 100% body weight and on a FT-1 min schedule. Animals at 80% reduced body weight without a schedule did not differ from rats self-injecting delta 9-THC at free feeding situation. These findings suggest that rats without previous history of drug dependence self-administer low doses of delta 9-THC and that the interaction between the food deprivation state and the environmental contingencies introduced by a FT-1 min schedule is a critical variable in the acquisition period.

Animals↗
PubMed1979

Intraventricular self-administration of acetaldehyde, but not ethanol, in naive laboratory rats.

For 11 consecutive days, naive rats were maintained in operant chambers where they were given the opportunity to self-administer acetaldehyde (1,2, or 5% v/v), ethanol (2 or 10% v/v), or pH control solutions directly into the cerebral ventricles. Only the animals that had access to the 2 and 5% acetaldehyde solutions showed rates of lever pressing significantly higher than controls. It is suggested that acetaldehyde rather than ethanol itself may mediate the positive reinforcing effects of ethanol in the brain.

Acetaldehyde↗