Reduction of predatory aggression of rats following administration of delta-9-tetrahydrocannabinol

Illicit drug use and violence

This chapter reviews evidence on the relationship between illicit drug use and violence, specifically cannabis, stimulant drugs, and opioids. It summarizes findings of systematic reviews of evidence on cannabis, stimulant drugs, and opioids. It also examines evidence from epidemiological studies of drug use among violent offenders and of violence among persons who use drugs, intervention studies, animal studies, human laboratory studies, and human neuroimaging studies. More studies have examined cannabis because of its higher prevalence of use. There is an association between cannabis use and violence, suggestive evidence of a dose-response relationship between the frequency of cannabis use and violence, and a stronger association in persons with psychoses. There is similar emerging evidence on stimulant use and violence, but evidence on opioids is very limited. There is limited and mixed evidence from intervention studies that reducing drug use reduces violence. Animal and human studies provide potential biological explanations for these associations. The association between cannabis use and violence is most consistent but limited by study heterogeneity and lack of control for potential confounders. It is unclear whether these associations are causal or reflect reverse causation or the effects of confounding.

The Relevance of Sex in the Association of Synthetic Cannabinoid Use With Psychosis and Agitation in an Inpatient Population

BACKGROUND

Current evidence suggests that women are more sensitive to the effects of cannabinoids. The aim of this study was to investigate the relevance of sex in the association of synthetic cannabinoid (SC) use with psychosis and agitation.

METHODS

A retrospective chart review was conducted for patients admitted to a psychiatric unit (2014-2016) to extract information on demographic factors, use of substances, clinical symptoms, and pharmacologic treatments. Study groups were defined as SC users (anyone who reported use of SCs over the past 3 months), cannabis users (positive toxicology screen for Δ⁹-tetrahydrocannabinol [THC]), and controls (those who denied use of SCs over the past 3 months and had negative toxicology for THC).

RESULTS

Digital charts of 983 patients were reviewed. A total of 162 subjects reported use of SCs over the past 3 months (76% male), and 292 subjects had positive toxicology screen for THC (67% male). A total of 38.9% of SC users (n = 63) had positive urine toxicology screen for THC. SC users had higher risks of psychotic presentations (adjusted odds ratio [AOR] = 3.390; 95% CI, 1.390-8.267) and agitation (AOR = 4.643; 95% CI, 1.974-10.918) compared to the controls. While women had lower rates of psychosis than men in the cannabis and control groups, the rates were markedly potentiated with SC use to high levels (79%) approximately equal to that seen in men (80%). There was also a significant interaction between SC use and sex for agitation (AOR = 0.308; 95% CI, 0.117-0.808). Female SC users were significantly more agitated than male SC users (73.7% vs 47.6%, respectively, P = .005).

CONCLUSIONS

SC users are more likely than nonusers to be psychotic or agitated in an inpatient setting. The potentiated rates of psychosis and agitation with SC use in women suggest that they may have a greater sensitivity to these synthetic compounds.​.

Chronic delta 9-tetrahydrocannabinol administration and schedule-induced aggression

The effects of 0.5 mg/kg and 1.0 mg/kg of delta 9-tetrahydrocannabinol (delta 9-THC) on key-pecking maintained by a response-initiated fixed interval (FI) schedule of food presentation and schedule-induced aggression in the pigeon were studied. Initially, following the administration of delta 9-THC both the rate of key-pecking and attack responding were markedly reduced. Over sessions, tolerance developed to the suppressant effect on key-pecking, with the rate returning to the predrug level. The suppressing effect of delta 9-THC on the rate of attack remained at or near zero throughout the series of delta 9-THC injections.

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.