Cortical inhibition and excitation in abstinent cocaine-dependent patients: a transcranial magnetic stimulation study.
Prior transcranial magnetic stimulation studies showed that resting motor threshold is elevated in abstinent cocaine-dependent patients, suggesting a decrease in axonal excitability. In contrast, the increased incidence of seizures and psychosis in this group suggests increased excitability or decreased inhibition. Here, we studied long-interval intracortical facilitation and long-interval intracortical inhibition, paired-pulse transcranial magnetic stimulation measures that are more directly linked to glutamatergic cortical facilitation and GABAergic inhibition, respectively. Ten cocaine-dependent and 10 healthy controls were examined. Resting motor threshold, long-interval intracortical facilitation and long-interval intracortical inhibition were tested from the left motor cortex. The cocaine group showed an elevated resting motor threshold and an increased long-interval intracortical facilitation, whereas long-interval intracortical inhibition was normal. Although the increase in long-interval intracortical facilitation suggests exaggerated cortical glutamatergic excitability, the increase in resting motor threshold may signify a protective mechanism against seizures and psychosis.
Sundaresan
Karthik
K
Department of Psychiatry and Behavioral Neurosciences, School of Medicine, Wayne State University, USA.
Ziemann
Ulf
U
Stanley
Jeff
J
Boutros
Nash
N
D000328:Adult; D001921:Brain / Q000187:drug effects / Q000503:physiopathology*; D003042:Cocaine / Q000009:adverse effects*; D019970:Cocaine-Related Disorders / Q000175:diagnosis / Q000503:physiopathology*; D018765:Dopamine Uptake Inhibitors / Q000009:adverse effects; D019054:Evoked Potentials, Motor / Q000502:physiology; D019706:Excitatory Postsynaptic Potentials / Q000187:drug effects / Q000502:physiology; D005260:Female; D018698:Glutamic Acid / Q000378:metabolism; D006801:Humans; D008297:Male; D008875:Middle Aged; D009044:Motor Cortex / Q000187:drug effects / Q000503:physiopathology; D009433:Neural Inhibition / Q000187:drug effects / Q000502:physiology; D013375:Substance Withdrawal Syndrome / Q000175:diagnosis / Q000503:physiopathology*; D009435:Synaptic Transmission / Q000187:drug effects / Q000502:physiology; D050781:Transcranial Magnetic Stimulation; D005680:gamma-Aminobutyric Acid / Q000378:metabolism
D018765:Dopamine Uptake Inhibitors; D018698:Glutamic Acid; D005680:gamma-Aminobutyric Acid; D003042:Cocaine