Biology subjects

Quansah Amissah, R.

Publications and source records attributed to Quansah Amissah, R..

3 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↗

bioRxiv2019

Differential expression of deltaFosB in reward processing regions between binge eating prone and resistant female rats

Binge eating disorder (BED) is characterized by bingeing and compulsivity. Even though BED is the most prevalent eating disorder, little is known about its pathophysiology. We aimed to identify brain regions and neuron subtypes implicated in the development of binge-like eating in a female rat model. We separated rats into binge eating prone (BEP) and binge eating resistant (BER) phenotypes based on the amount of sucrose they consumed following foot-shock stress. We quantified deltaFosB ({Delta}FosB) expression to assess chronic neuronal activation during phenotyping. The number of {Delta}FosB-expressing neurons was: 1) higher in BEP than BER rats in reward processing areas (medial prefrontal cortex (mPFC), nucleus accumbens (Acb), and ventral tegmental area (VTA)); 2) similar in taste processing areas (insular cortex and parabrachial nucleus); 3) higher in the paraventricular nucleus of BEP than BER rats, but not different in the locus coeruleus, which are stress processing structures. To study subtypes of {Delta}FosB-expressing neurons in the reward system, we performed in situ hybridization for glutamate decarboxylase 65 and tyrosine hydroxylase mRNA after {Delta}FosB immunohistochemistry. In the mPFC and Acb, the proportions of gamma-aminobutyric acidergic (GABAergic) and non-GABAergic {Delta}FosB-expressing neurons were similar in BER and BEP rats. In the VTA, while the proportion of dopaminergic {Delta}FosB-expressing neurons was similar in both phenotypes, the proportion of GABAergic {Delta}FosB-expressing neurons was higher in BER than BEP rats. Our results suggest that reward processing brain regions, particularly the VTA, are important for the development of binge-like eating.\n\nSignificanceBecause {Delta}FosB expression is associated with a reduction of activity in neurons, a higher expression of {Delta}FosB in the mPFC, Acb, and VTA of binge eating prone rats compared to binge eating resistant rats suggests a decrease in neuronal activity in these regions, which is consistent with results observed in neuroimaging studies in binge eating disorder patients. This decrease in activity due to {Delta}FosB expression may underlie the compulsivity and overconsumption of palatable food observed in both our rat model of binge-like eating and binge eating disorder patients.

neuroscience↗