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Medical AI Inquiry: You was designed to assist in medical decision-making based on the provided user questions. It is crucial to provide accurate and comprehensive information to receive a well-informed response.  Labels: BACKGROUND, METHODS, RESULTS. Meshes: Adult, Alleles, Case-Control Studies, Cerebral Cortex, Cortical Spreading Depression, Electromyography, Evoked Potentials, Motor, Female, Functional Laterality, Genetic Variation, Humans, Male, Reaction Time, Serotonin Plasma Membrane Transport Proteins, Time Factors, Transcranial Magnetic Stimulation, Young Adult.
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Does allelic variation in the serotonin transporter promoter modulate cortical excitability? Context: Transcranial magnetic stimulation (TMS) is a noninvasive procedure that may be used to study individual differences in motor cortex excitability. Such differences are assumed to reflect serotonergic and other inputs to the motor cortex. Here we investigate the impact of a functional polymorphism in the promoter region of the 5-hydroxytryptamine transporter gene (5-HTTLPR) on measures of motor cortex excitability. Sixty healthy subjects carrying one or two copies of the short 5-HTTLPR allele (s/s and s/l) showed a significant reduction in short intracortical inhibition (SICI, p = .012) and an increased cortical silent period (p = .042) compared with 60 age- and sex-matched individuals homozygous for the long allele (l/l). In contrast, motor threshold and intracortical facilitation did not differ significantly between groups.
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These results provide further evidence of a role for serotonergic transmission in the modulation of cortical excitability. Differential effects on the measures under study suggest a pattern of prioritization in bioamine regulation of cortical inhibition. Final Decision: yes