title: A transcranial magnetic stimulation study of the effects of cannabis use on motor cortical inhibition and excitability.
abstract: Active compounds in cannabis such as tetrahydrocannabinol (THC) interact with the inhibitory neurotransmitter delta-aminobutyric acid (GABA) but little is known about the functional effects of cannabis on human cortical brain processes. Therefore, the aim of the study was to investigate whether patients with chronic cannabis use demonstrate abnormalities in cortical inhibition or excitability. In all, 42 chronic cannabis using subjects (divided into heavy and light using subjects) and 19 controls were included in the study. Single and paired pulse transcranial magnetic stimulation were used to assess a number of parameters of cortical inhibition and cortical excitability. In addition, psychomotor function and THC plasma levels were measured. Both cannabis using groups (heavy and light use) demonstrated a reduction in short interval cortical inhibition compared with healthy controls, but there was no difference in other measures of cortical inhibition or cortical excitability. There was also no difference between the two groups on measures of psychomotor performance. Chronic cannabis use is associated with a reduction in cortical inhibition potentially related to activity at the GABA(A) receptors. Further research is required to explore whether this results from chronic cannabis use or reflects an underlying predisposition to developing chronic substance use problems.
authors: Alfred Psychiatry Research Centre, The Alfred and Monash University School of Psychology, Psychiatry and Psychological Medicine, Commercial Rd Melbourne, Victoria, Australia. paul.fitzgerald@med.monash.edu.au
authors: Paul B
authors: PB
authors: Fitzgerald
authors: Suzanne
authors: S
authors: Williams
authors: Zafiris J
authors: ZJ
authors: Daskalakis
mesh_terms: D000328:Adult; D000704:Analysis of Variance; D013759:Dronabinol / Q000097:blood; D004576:Electromyography; D019054:Evoked Potentials, Motor; D005260:Female; D006225:Hand; D006801:Humans; D008297:Male; D002189:Marijuana Abuse / Q000097:blood / Q000503:physiopathology*; D009044:Motor Cortex / Q000187:drug effects / Q000503:physiopathology*; D009433:Neural Inhibition / Q000187:drug effects / Q000502:physiology*; D009483:Neuropsychological Tests; D011597:Psychomotor Performance / Q000187:drug effects / Q000502:physiology; D011795:Surveys and Questionnaires; D013997:Time Factors; D050781:Transcranial Magnetic Stimulation
chemical_list: D013759:Dronabinol