THC induced similar physiological effects on HIV transgenic rats and their controls without affecting HIV-induced deficits in effortful motivation.

Delta-9-tetrahydrocannabinol (THC), the main psychoactive component of cannabis, reduced pain sensitivity, body temperature, and movement in HIV-1 transgenic rats and their controls, with some differences between males and females. A higher dose (3 mg/kg) also temporarily lowered motivation to work for a reward, but this effect disappeared after 16 days of daily treatment. HIV-1 transgenic rats showed lower motivation than one control strain (Fischer344) but not another (wildtype littermates), highlighting the importance of choosing appropriate control groups in research.

Study at a glance

Abstract

Cannabinoids have proven to useful for attenuating adverse effects of HIV. People living with HIV use cannabis at higher rates, with evidence suggesting it alleviates physiological symptoms such as nausea, loss of appetite, etc.. Cannabis can alter physiology as well as essential behavioral functions such as motivation. This study investigated the effect of delta-9-tetrahydrocannabinol (THC), the main psychoactive component of cannabis, on physiological responses and motivation in HIV-1 transgenic (tg) rats and their controls. In Experiment 1, adult female and male HIV-1tg (n = 46) rats and their controls (wildtype littermates [WT] and Fischer344 [F344] rats; n = 87) were tested for acute THC-induced (0, 0.3, 3 mg/kg) physiological effects using the cannabinoid tetrad assay: 1) nociception, 2) body temperature, and 3) locomotor and exploratory behavior. In Experiment 2, adult female and male HIV-1tg (n = 58) rats and controls (n = 84) were tested in the Progressive Ratio Breakpoint Task (PRBT) to assess effortful motivation at baseline, after acute THC, then chronic (16 days) THC treatment (0, 0.3, 3 mg/kg). Data collected was analyzed using separate univariate ANOVA test with group (HIV-1tg, WT, F344), drug (0, 0.3, 3 mg/kg THC) and sex (female and male) as fixed factors. Bonferroni adjustments were used to correct for multiple comparisons. THC (3 mg/kg) reduced nociception, temperature, and locomotor and exploratory activity across genotypes with some sex-dependent effects. Further, HIV-1tg and WT rats showed reduced motivation compared to F344 controls across PRBT testing timepoints. Acute 3 mg/kg THC reduced breakpoints but with no effects after chronic treatment. Hence, THC produces consistent physiological and motivational across HIV-1tg rats and their controls. Additionally, the HIV-1tg rat exhibited motivational deficits only when compared to the F344 but not WT controls, suggesting careful selections of control groups in future studies.