Ovarian hormones and cortical excitability. An rTMS study in humans.
OBJECTIVE
Ovarian steroids influence neural excitability. Using repetitive transcranial magnetic stimulation (rTMS) we investigated changes in cortical excitability during the menstrual cycle.


METHODS
Eight women underwent rTMS on Days 1 and 14 of the menstrual cycle. As a control group, 8 age-matched men were also tested twice, with a 14-day interval between the two experimental sessions. Repetitive magnetic pulses were delivered in trains of 10 stimuli (5 Hz frequency and 120% of the motor threshold calculated at rest) to the left motor area of the first dorsal interosseous muscle.


RESULTS
In women, the motor evoked potential (MEP) size did not increase on Day 1, but it increased progressively during the train on Day 14. The duration of the silent period progressively lengthened during the train on both days. In men the MEP increased in size, and the silent period lengthened to a similar extent on both days.


CONCLUSIONS
In women, hormone changes related to the menstrual cycle alter cortical excitability.


CONCLUSIONS
Low estrogen levels probably reduce cortical excitability because their diminished action on sodium channels reduces recruitment of excitatory interneurons during rTMS thus abolishing the MEP facilitation.
Inghilleri
M
M
Department of Neurological Sciences, University of Rome La Sapienza, Viale dell'Università 30, 00185 Rome, Italy. maurizio.inghilleri@uniroma1.it
Conte
A
A
Currà
A
A
Frasca
V
V
Lorenzano
C
C
Berardelli
A
A
D000328:Adult; D000704:Analysis of Variance; D002540:Cerebral Cortex / Q000502:physiology*; D004558:Electric Stimulation / Q000379:methods; D019054:Evoked Potentials, Motor; D005260:Female; D006728:Hormones / Q000502:physiology*; D006801:Humans; D008280:Magnetics; D008297:Male; D008597:Menstrual Cycle / Q000378:metabolism*; D010053:Ovary / Q000378:metabolism*
D006728:Hormones