Intracortical excitability is modulated by a norepinephrine-reuptake inhibitor as measured with paired-pulse transcranial magnetic stimulation.
OBJECTIVE
Paired-pulse transcranial magnetic stimulation (ppTMS) of the motor cortex can be used to measure intracortical inhibition and facilitation of evoked motor potentials dependent on different interstimulus intervals (ISI). The reuptake-inhibition of norepinephrine, known as an excitatory neuromodulator and neurotransmitter, was postulated to enhance cortical excitability through increased facilitation and reduced inhibition as measured with ppTMS.


METHODS
Eight healthy subjects were examined with ppTMS at ISIs of 2, 3, 4, 5, 6, 7, 8, 10, 15 and 20 ms before and approximately 1.5 h after ingestion of 8 mg reboxetine. The group effects at the different ISIs pre/post reboxetine intake were analysed.


RESULTS
Post-reboxetine ppTMS showed an enhanced intracortical facilitation effect at ISIs of 8, 10, 15 and 20 ms. A decreased inhibition was found at an ISI of 3 ms.


CONCLUSIONS
Reboxetine-induced higher postsynaptic norepinephrine level enhances intracortical excitability as measured with ppTMS. This finding provides new perspectives for evaluating neurophysiological properties of antidepressive medication and for investigating the pathophysiology of depression.
Herwig
Uwe
U
Department of Psychiatry, University of Ulm, Leimgrubenweg 12, 89070 Ulm, Germany. uwe.herwig@medizin.uni-ulm.de
Bräuer
Kerstin
K
Connemann
Bernhard
B
Spitzer
Manfred
M
Schönfeldt-Lecuona
Carlos
C
D018759:Adrenergic Uptake Inhibitors / Q000494:pharmacology*; D000328:Adult; D004305:Dose-Response Relationship, Drug; D004558:Electric Stimulation; D004574:Electromagnetic Fields; D005071:Evoked Potentials; D005260:Female; D006801:Humans; D008297:Male; D009025:Morpholines / Q000494:pharmacology*; D009044:Motor Cortex / Q000187:drug effects* / Q000502:physiology; D000077593:Reboxetine; D013997:Time Factors
D018759:Adrenergic Uptake Inhibitors; D009025:Morpholines; D000077593:Reboxetine