Delta9-tetrahydrocannabinol induced inhibition of predatory aggression in the rat

Marijuana withdrawal and aggression among a representative sample of U.S. marijuana users

BACKGROUND

Previous laboratory-based research suggests that withdrawal from marijuana may cause increased aggression. It is unclear whether this finding extends beyond the laboratory setting to the general population of marijuana users. The purpose of this study was to test a cross-sectional association between marijuana withdrawal symptoms and aggression among a representative sample of U.S. adult marijuana users, and to test whether this association was moderated by previous history of aggression.

METHODS

Data were analyzed from the National Epidemiologic Survey on Alcohol and Related Conditions. Wave Two data (2004-2005) were used for all variables except for history of aggression, which was assessed during the Wave One interview (2001-2002). Two outcomes were examined: self-report general aggression and relationship aggression. Odds ratios for aggression based on withdrawal symptoms and the interaction between withdrawal symptoms and history of aggression were calculated using logistic regression, adjusting for covariates and accounting for the complex survey design.

RESULTS

Among marijuana users with a history of aggression, marijuana withdrawal was associated with approximately 60% higher odds of past year relationship aggression (p<0.05). There was no association between withdrawal symptoms and relationship aggression among those without a history of aggression, and no association with general aggression regardless of history of aggression.

CONCLUSIONS

The findings from this study support the notion that laboratory-based increases in aggression due to marijuana withdrawal extend to the general population of marijuana users who have a previous history of aggression.

Anticonvulsant action of cannabis in the rat: role of brain monoamines

The role of brain monoamines in the anticonvulsant action of Cannabis indica resin (CI), against maximal electroshock-induced seizures in albino rats, was investigated by using pharmacologic agents that influence brain monoamine activity. Delta-9-tetrahydrocannabinol content of cannabis resin was estimated to be 17%. The anticonvulsant action of CI (200 mg/kg, i.p.) was significantly inhibited after pretreatment with drugs that reduce brain serotonin activity but not by drugs that reduce brain catecholamine activity. Similarly, the anticonvulsant action of a subanticonvulsant dose (50 mg/kg, i.p.) of CI was potentiated by serotonin precursors but not by catecholamine precursors. Potentiation of the anticonvulsant action of CI by nialamide or by imipramine was inhibited after pretreatment with 5,6-dihydroxytryptamine. The results suggest that the anticonvulsant action of CI in the rat is serotonin- and not catecholamine-mediated.

Time course of delta9-tetrahydrocannabinol inhibition of predatory aggression

Three studies assessed the time course of inhibition of predatory aggression and changes in levels of brain serotonin following administration of delta9-THC. In Study One, six groups of six rats each were administered 1.25 mg/kg delta9-THC IV and frog-killing behavior was measured at six postinjection intervals: 30, 60, 90, 150, 210, and 270 minutes. In Study Two, four groups of six rats each were tested. Group One received a vehicle control injection and was tested immediately, i.e. zero-minutes, postinjection. The remaining groups received 1.25 mg/kg delta9-THC, and behavior was measured at 0, 15, and 30 min postinjection. In Study Three, two groups of six rats were treated with the vehicle or 1.25 mg/kg delta9-THC and sacrificed one minute postinjection. Additional drug groups were sacrificed at 30 and 210 min postinjection. Levels of 5-HT were determined in four brain sections: cortex, midbrain, medulla, and cerebellum. Significant inhibition of predatory aggression was found for groups tested at 0, 15, and 30 min postinjection. Brain levels of 5-HT in the midbrain and/or medulla were significantly increased over the same period.

Mouse-killing and motor activity: effects of chronic delta9-tetrahydrocannabinol and pilocarpine

Chronic administration of delta9-tetrahydrocannabinol (THC) for 5--8 weeks at 4 dose levels (2, 10, 20, 50mg/kg/day) or of pilocarpine (12.5, 25 mg/kg/day) for 3 weeks induced mouse-killing in 25--70% of previously "non-killer" rats of the Sprague-Dawley strain. The maximum percent of drug-induced mouse-killing depended on the daily dose and housing conditions, 20mg/kg/day THC and 25 mg/kg/day pilocarpine in single-housed rats being the most effective treatments. Drug-induced mouse-killing appeared to be a form of behavioral pathology, differing from the species-specific predatory response, when it first appeared. Concurrent assessment of locomotor and rearing activities showed dose-dependent depressant effects of THC and pilocarpine without evidence for tolerance. Different dose-dependencies and time courses suggest that changes in motor activities are not directly linked to the appearance of the killing behavior.