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Abstinence from chronic methylphenidate exposure modifies cannabinoid receptor 1 levels in the brain in a dose-dependent manner

Author(s):

Carly Connor, John Hamilton, Lisa Robison, Michael Hadjiargyrou, David Komatsu and Panayotis Thanos*  

Abstract:


Introduction: Methylphenidate (MP) is a widely used psychostimulant prescribed for Attention Deficit Hyperactivity Disorder, and is also used illicitly by healthy individuals. Chronic exposure to MP has been shown to affect physiology, behavior, and neurochemistry.

Methods: The present study examined its effect on the endocannabinoid system. Adolescent rats had daily oral access to either water (control), low dose MP (4/10 mg/kg), or high dose MP (30/60 mg/kg). After 13 weeks of exposure, half of the rats in each group were euthanized, however the remaining rats underwent a four-week long abstinence period. Cannabinoid receptor 1 binding (CB1) was measured with in vitro autoradiography using [3H] SR141716A.

Results: Rats who underwent a 4-week abstinence period after exposure to chronic HD MP showed increased binding compared to rats with no abstinence period in several cortical and basal ganglia regions of the brain. In contrast to this, rats who underwent a 4-week abstinence period after exposure to chronic LD MP showed lower binding compared to rats with no abstinence period in mainly the basal ganglia regions and in the hindlimb region of the somatosensory cortex. Following 4 weeks of drug abstinence, rats who were previously given HD MP showed higher [ 3H] SR141716A binding than rats given LD MP in many of the cortical and basal ganglia regions examined. These results highlight biphasic effects of MP treatment on cannabinoid receptor levels. Abstinence from HD MP seemed to increase CB1 receptor levels while abstinence from LD MP seemed to decrease CB1 levels.

Conclusion: Given the prolific expression of cannabinoid receptors throughout the brain, many types of behaviors may be affected as a result of MP abstinence. Further research will be needed to help identify these behavioral changes.

Keywords:

methylphenidate, Ritalin, psychostimulant, endocannabinoid system, cannabinoid receptor 1, Attention Deficit Hyperactivity Disorder

Affiliation:

Behavioral Neuropharmacology and Neuroimaging Laboratory on Addictions, Clinical Research Institute on Addictions, Department of Pharmacology and Toxicology, Jacobs School of Medicine and Biosciences, University at Buffalo, Buffalo, NY, Behavioral Neuropharmacology and Neuroimaging Laboratory on Addictions, Clinical Research Institute on Addictions, Department of Pharmacology and Toxicology, Jacobs School of Medicine and Biosciences, University at Buffalo, Buffalo, NY, Department of Neuroscience and Experimental Techniques, Albany Medical College, Albany, NY, Department of Life Sciences, New York Institute of Technology, Old Westbury, NY, Department of Orthopedics, Stony Brook University, Stony Brook, NY, Behavioral Neuropharmacology and Neuroimaging Laboratory on Addictions, Clinical Research Institute on Addictions, Department of Pharmacology and Toxicology, Jacobs School of Medicine and Biosciences, University at Buffalo, Buffalo, NY



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