Title:Abstinence from Chronic Methylphenidate Exposure Modifies Cannabinoid
Receptor 1 Levels in the Brain in a Dose-dependent Manner
Volume: 28
Issue: 4
Author(s): Carly Connor, John Hamilton, Lisa Robison, Michael Hadjiargyrou, David Komatsu and Panayotis Thanos*
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,United States
Keywords:
Methylphenidate, ritalin, psychostimulant, endocannabinoid system, cannabinoid receptor 1, attention deficit hyperactivity disorder.
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 measures, 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, with 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
CB1 binding in several cortical and basal ganglia regions of the brain compared to rats with no abstinence period.
In contrast to this, rats who underwent a 4-week abstinence period after exposure to chronic LD MP
showed lower CB1 binding mainly in the basal ganglia regions and the hindlimb region of the somatosensory
cortex compared to rats with no abstinence period. Following 4 weeks of drug abstinence, rats who were previously
given HD MP showed higher [3H] SR141716A binding in many of the cortical and basal ganglia regions
examined than rats given LD MP. These results highlight the 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.