No abstract

Despite widespread cannabis use in humans, few rodent models exist demonstrating significant Δ⁹-tetrahydrocannabinol (THC) self-administration, possibly due to THC's co-occurring aversive effects, which impact drug reinforcement. Cannabis contains a number of phytocannabinoids in addition to THC, one of which, cannabidiol (CBD), has been reported to antagonize some of the aversive effects of THC. Given such effects of CBD, it is possible that it might influence THC intravenous self-administration in rodents. Accordingly, male and female Long-Evans rats were trained to self-administer THC over a 3-week period and then were assessed for the effects of CBD on responding for THC at 1:1 and 1:10 dose ratios or for the establishment of cocaine self-administration (as a positive control for drug self-administration). Consistent with previous research, THC self-administration was modest and only evident in a subset of animals (and unaffected by sex). Cocaine self-administration was high and evident in the majority of animals tested, indicating that the design was sensitive to drug reinforcement. There was no effect of CBD pretreatment on THC intravenous self-administration at any CBD:THC dose ratio. Future developments of animal models of THC self-administration and the examination of factors that affect its display remain important to establish procedures designed to assess the basis for and treatment of cannabis use and abuse. (PsycINFO Database Record

No abstract

No abstract

These studies examined adolescent nicotine preexposure effects on the rewarding and aversive effects of adult cocaine use and the relationship of these changes to self‐administration. In Experiment 1, rats on postnatal day (PND) 28 were divided into two groups and given daily 0.6 mg/kg injections of nicotine or vehicle until PND 42. Rats were given locomotor tests to examine nicotine‐induced sensitization. They were allowed to age untreated to PND 76, implanted with jugular catheters and allowed to recover for at least 5 days. On PND 90, cocaine self‐administration (0.25 or 0.75 mg/kg), progressive ratio (PR) responding, extinction and cue‐induced reinstatement testing began. Experiment 2 explored nicotine's impact on the balance of cocaine's affective properties. Rats (PND 28‐ 75) were treated as described above. On PND 76, they were tested for the aversive and rewarding effects of cocaine in a combined conditioned taste avoidance (CTA)/place preference (CPP) procedure. Rats were given access to a novel saccharin solution, injected with cocaine (5.6, 10 or 18 mg/kg) then placed in CPP chambers. In Experiment 1, the nicotine group showed sensitized locomotor activity over trials compared to controls, showing that the nicotine was behaviorally active. All rats in Experiment 1 showed clear, dose dependent responding during acquisition, PR, extinction and reinstatement, with no nicotine preexposure effect. In Experiment 2, rats showed a significant CTA trial x Drug effect (p = .012) with cocaine groups consuming less saccharin over trials with no preexposure or dose group differences. There was no significant CPP or interaction with preexposure. These studies suggest that adolescent nicotine preexposure does not have an impact on adult cocaine self‐administration or its affective properties under these parametric conditions.