Objective: To assess the addictive potential of cannabis by investigating the motivational responses of low dose delta-9-tetrahydrocannabinol (∆9-THC) and a marijuana tea extract (MTE); and to determine if the length of the conditioning period in the conditioned place preference (CPP) paradigm influences reward or aversion to these cannabinoid preparations.
Methods: Thirty-eight (38) Sprague-Dawley rats were taken through a biased CPP paradigm utilizing an eight-day schedule. The pre-conditioning phase consisted of three trials of 15 minutes each and the conditioning phase lasted either 40 or 18 minutes in the drug-paired, ‘non-preferred’, white chamber or the vehicle-paired, ‘preferred’ black chamber. Spontaneous motor activity (SMA) was used to determine the 18-minute conditioning period, dosage of a crude marijuana tea extract (MTE) and the oil-based vehicle for ∆9-THC (coconut oil), which did not alter the SMA of the rats. Differences in the mean times spent in the ‘non-preferred’ white chamber during the pre-conditioning and post-conditioning periods were compared using paired t-test.
Results: Significant place aversion (p < 0.0001) to the MTE occurred at the 40-min conditioning period, but not at the 18-min period. Also, significant CPP reward (p < 0.01) to 0.05 mg/kg ∆9-THC occurred with the reduced 18-min conditioning period, while a non-significant increase in post-conditioning time at the higher dose of 2.0 mg/kg ∆9-THC was obtained.
Conclusion: Drug-seeking, motivational reward to 0.05 mg/kg ∆9-THC confirms the addictive potential of this psychoactive agent. However, duration of the conditioning period in the CPP design is a determinant of outcome to CPP-reward or aversion to marijuana.
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