Characterizing the Effects of Chronic Cannabis Vapour Exposure and Withdrawal on Cannabinoid Triad, Somatic Signs and Behavioural Network Reorganization Adult Male Rats
RationaleCannabis withdrawal contributes to relapse in individuals with cannabis use disorder, yet preclinical studies have largely focused on withdrawal induced by injected cannabinoids rather than inhaled cannabis, which remains the most common route in humans. The behavioural effects of chronic exposure to vapourized cannabis flower and resulting withdrawal after cessation of exposure remain poorly characterized. ObjectivesTo determine the behavioural effects of chronic vapourized high-THC cannabis flower exposure on cannabinoid tetrad, somatic withdrawal and behavioural transition networks in rats following both chronic vapour exposure and administration of the cannabinoid receptor 1 (CB1) receptor antagonist SR141716A (rimonabant). MethodsTwo studies were conducted using adult male Sprague Dawley rats. The first study (N = 16) exposed rats to either air or vapourized high-THC cannabis flower three times a day for seven days using a Volcano vapourizer, followed by intraperitoneal administration of the CB1 antagonist SR141716A (3 mg/kg). The second study (N = 24) included two air controls and two cannabis groups, with one of each receiving either saline or SR141716A. Behavioural assessments included triad measurements to confirm the cannabis effect, along with withdrawal assessment via a sucrose preference test and somatic signs 30 minutes following rimonabant administration. ResultsRepeated cannabis vapour exposure produced reduced locomotor activity, hypothermia, and increased tail-flick latency. Rimonabant administration precipitated withdrawal characterized by increased total withdrawal scores and somatic signs, including blinking, body shakes/tremors, and grooming-related behaviours. Behavioural network analyses revealed substantial reorganization of behavioural transition structure during both chronic cannabis exposure and withdrawal. Chronic cannabis exposure was associated with reduced network modularity, a condensed behavioural repertoire, and altered behavioural centrality measures. At the same time, precipitated withdrawal further increased the influence of exploratory behaviours, particularly sniffing, and reduced the network prominence of locomotor-associated behaviours, such as walking, beyond that detected using conventional behavioural measures alone. ConclusionChronic exposure to vapourized cannabis flower followed by CB1 receptor antagonism produces reliable withdrawal symptoms in rats. Behavioural network analyses further reveal that cannabis exposure and withdrawal are both associated with widespread reorganization of behavioural dynamics, suggesting that withdrawal alters not only individual behaviours but also the structure of behavioural transitions. These findings establish a translational model of cannabis withdrawal using inhaled cannabis flower vapour and identify behavioural network analysis as a sensitive approach for characterizing withdrawal-related behavioural states.