Stress, marijuana and addiction in an animal model [abstract]

ABSTRACT

OBJECTIVE: Acute stress has been shown in rats to increase self-administration for drugs such as cocaine, morphine and amphetamine. We aimed to explore this phenomenon for marijuana extract (ME) and its psychoactive component, 9-tetra-hydrocannabinol ( 9 THC). METHODS: Six female Sprague Dawley rats were followed free access to a black grid-floored chamber and a white one with a floor strewn with wood shavings. The time spent in each chamber indicated a preference for the black chamber. On alternate days of an 8-day conditioning period, six Sprague Dawley rats were first subjected to an acute stress for 10 minutes followed by an intraperitoneal administration of ME (saline vehicle) or 2m/kg 9 THC (oil vehicle). The doses used were those which had been previously shown to have neither aversive nor rewarding effects. The rats were then confined to the white chamber. On the other days, the rats were administered the respective vehicle and confined to the black chamber. After this conditioning period, the rats were once again allowed free access to the chambers and the pre-conditioning period times in each chamber were compared to the post-conditioning times. The stressors were restraint stress (RS), swimming stress (SS) or acute isolation stress (ACI). RESULTS: When ME was administered with RS, the mean time spent in the drug+stress chamber increased compared with the pre-conditioning time with a significance level of p= 0.07. This result was repeated with 2 mg/kg of 9-tetrahydrocannabinol (p= 0.07). The ACI + ME combination resulted in an increase, which was significant (p< 0.05). CONCLUSIONS: Our results provide some evidence to support a possible influence of acute stress on reward to marijuana. There is also some indication that different types of stressors have different effects on this stress and drug reward association. (AU)