Biology subjects

Khokhar, J.

Publications and source records attributed to Khokhar, J..

5 recordsLinked to original sources

bioRxiv2026

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.

neuroscience↗

bioRxiv2025

A simple, open-source restraint system for magnetic resonance imaging in awake rats

Magnetic resonance imaging (MRI) is a critical tool for translational neuroscience, offering cross-species insights into brain structure and function; however, its application in preclinical research is constrained by routine anesthesia use or sedation, which alters neural activity and limits comparisons to awake human imaging. Awake rodent functional MRI (fMRI) provides a powerful platform for investigating brain function under physiologically relevant conditions, but implementation is limited by technical challenges, particularly head motion and stress during scanning. Most restraint systems employ initial anesthesia, compromising translatability of findings, and highlighting the need for improved designs. We developed a novel restraint system optimized for awake rat fMRI. The system consists of modular 3D-printed components and can be assembled in under five minutes. It is accompanied by a protocol that includes head-post implantation followed by an 11-day habituation period post-surgical recovery. The system eliminates the need for isoflurane anesthesia, ear bars, and bite bars, reducing stress and improving animal comfort. It supports integration with behavioral paradigms such as pupil tracking and licking responses. High-resolution T2-weighted anatomical images and functional scans obtained using the system showed excellent spatial clarity and minimal motion artifacts. Quality control metrics, including head motion parameters and temporal signal-to-noise ratio, confirmed the systems stability and suitability for awake imaging. Functional connectivity analysis revealed robust positive correlations between functionally relevant regions. This system offers a scalable, reproducible, and animal-friendly solution for awake rat fMRI. While the current design limits direct cranial access for multimodal recordings, it enables high-quality, behaviorally enriched imaging without anesthesia. Significance Statement: Most rodent fMRI studies, including awake studies, rely on anesthesia, which profoundly alters brain activity and limits the interpretation of the data. This study presents a novel restraint system that enables high-quality fMRI in fully awake rats, eliminating the need for anesthesia, ear bars, and bite bars. By reducing stress and motion, this simple restraint system allows for investigation of neural activity and connectivity without confounds from sedation or anesthesia. Its open-source, modular design supports behavioral tasks and broad accessibility, making it a valuable tool for neuroscience research seeking to bridge the gap between preclinical imaging and real-world brain function.

neuroscience↗

bioRxiv2022

Maternal immune activation and adolescent alcohol exposure increases alcohol drinking and disrupts cortical-striatal-hippocampal oscillations in adult offspring

Maternal immune activation (MIA) is strongly associated with an increased risk of developing mental illness in adulthood, which often co-occurs with alcohol misuse. The current study aimed to begin to determine whether MIA, combined with adolescent alcohol exposure (AE), could be used as a model with which we could study the neurobiological mechanisms behind such co-occurring disorders. Pregnant Sprague-Dawley rats were treated with PolyI:C or saline on gestational day 15. Half of the offspring were given continuous access to alcohol during adolescence, leading to four experimental groups: controls, MIA, AE, and Dual (MIA + AE). We then evaluated whether MIA and/or AE alters: 1) alcohol consumption; and 2) cortical-striatal-hippocampal oscillations in adult offspring. Dual rats, particularly females, drank significantly more alcohol in adulthood compared to all other groups. Using machine learning to build predictive models from oscillations, we were able to differentiate Dual rats from control rats and AE rats in both sexes, and Dual rats from MIA rats in females. The current data suggest that MIA+AE (Dual "hits") is a valuable model that we can use to study the neurobiological underpinnings of co-occurring disorders. Our future work aims to extend these findings to other addictive substances to enhance the translational relevance of this model.

neuroscience↗

bioRxiv2022

Interference of Neuronal TrkB Signaling by the Cannabis-Derived Flavonoids Cannflavins A and B

Cannflavins A and B are flavonoids that accumulate in the Cannabis sativa plant. These specialized metabolites are uniquely prenylated and highly lipophilic, which, a priori, may permit their interaction with membrane-bound enzymes and receptors. Although previous studies found that cannflavins can produce anti-inflammatory responses by inhibiting the biosynthesis of pro- inflammatory mediators, the full extent of their cellular influence remains to be understood. Here, we studied these flavonoids in relation to the Tropomyosin receptor kinase B (TrkB), a receptor tyrosine kinase that is activated by the growth factor brain-derived neurotrophic factor (BDNF). Using mouse primary cortical neurons, we first collected evidence that cannflavins prevent the accumulation of Activity-regulated cytoskeleton-associated (Arc, also known as Arg3.1) protein upon TrkB stimulation by exogenous BDNF in these cells. Consistent with this effect, we also observed a reduced activation of TrkB and downstream signaling effectors that mediate Arc mRNA transcription when BDNF was co-applied with the cannflavins. Of note, we also performed a high-throughput screen that demonstrated a lack of agonist action of cannflavins towards 320 different G protein-coupled receptors, a result that specifically limit the possibility of a TrkB transinactivation scenario via G protein signaling to explain our results with dissociated neurons. Finally, we used Neuro2a cells overexpressing TrkB to show that cannflavins can block the growth of neurites and increased survival rate produced by the higher abundance of the receptor in this model. Taken together, our study offers a new path to understand the reported effects of cannflavins and other closely related compounds in different cellular contexts.

pharmacology and toxicology↗

bioRxiv2021

Alcohol and Vapourized Nicotine Co-Exposure During Adolescence Contribute Differentially to Sex-Specific Behavioural Effects in Adulthood

IntroductionCo-occurrence of e-cigarette use and alcohol consumption during adolescence is frequent. However, little is known about their long-lasting effects when combined. Here, we examined whether adolescent co-exposure to alcohol drinking and vapourized nicotine would impact reward- and cognition-related behaviours in adult male and female rats during adulthood. MethodsFour groups of male and female Sprague Dawley rats (n=8-11/group/sex) received either nicotine (JUUL 5% nicotine pods) or vehicle vapour daily between postnatal days 30-46, while having continuous voluntary access to ethanol and water during this time in a two-bottle preference design. Upon reaching adulthood, rats underwent behavioural testing utilizing Pavlovian conditioned approach testing, fear conditioning and a two-bottle alcohol preference test. ResultsA sex-dependent effect was found in the two-bottle preference test in adulthood such that females had a higher intake and preference for alcohol compared to males regardless of adolescent exposure; both male and female adult rats had greater alcohol preference compared to adolescents. Male rats exposed to vapourized nicotine with or without alcohol drinking during adolescence exhibited altered reward-related learning in adulthood, evidenced by enhanced levels of sign-tracking behaviour. Male rats that drank alcohol with or without nicotine vapour in adolescence showed deficits in associative fear learning and memory as adults. In contrast, these effects were not seen in female rats exposed to alcohol and nicotine vapour during adolescence. ConclusionsThe present study provides evidence that co-exposure to alcohol and vapourized nicotine during adolescence in male, but not female, rats produces longterm changes in reward- and cognition-related behaviours. ImplicationsThese findings enhance our understanding of the effects of alcohol drinking and nicotine vapour exposure in adolescence. Moreover, they highlight potential sex differences that exist in the response to alcohol and nicotine vapour, underscoring the need for follow-up studies elucidating the neurobiological mechanisms that drive these sex differences, as well as the long-term effects of alcohol and nicotine vapour use.

neuroscience↗