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Published on: August 16, 2021
The effects of caffeine on short-latency afferent inhibition measured with paired-pulse conventional and
Camilla Carrozzo1, Martina Cannazza1, Diletta Fratini1
1Department of Clinical Neurophysiology, Aarhus University Hospital, Aarhus, Denmark; Unit of Neurology, Neurophysiology, Neurobiology, and Psychiatry Department of Medicine and Surgery, Università Campus Bio-Medico Di Roma, Via Alvaro del Portillo, Rome, Italy.
Objective:
Transcranial Magnetic Stimulation (TMS) tests of Short-latency Afferent Inhibition (SAI) by conventional amplitude (A-SAI) and threshold-tracking (T-SAI) are important methods to investigate cortical excitability and, more specifically, sensory motor-integration. Since beverages containing caffeine are widely consumed, and caffeine has been reported to affect cortical excitability, it is of interest to explore if SAI is modulated by caffeine.
Methods:
Twenty healthy subjects (11 females, 9 males; mean age: 27.0 ± 5.53) were studied in a single fixed-dose randomized double-blind placebo-controlled cross-over trial of 200 mg caffeine or placebo administered as chewing gum. Changes in A-SAI and T-SAI at 12 interstimulus intervals between 18 ms and 30 ms were assessed by conventional fixed stimulus and threshold-tracking techniques.
Results:
There was no effect of caffeine on SAI across the full range of ISIs with either of the methods. However, caffeine significantly enhanced peak A-SAI (ISIs 19-21 ms) when compared to placebo (p = 0.011), while no effect on peak T-SAI was found.
Conclusion:
Caffeine enhances SAI as evaluated with the conventional A-SAI protocol, but not with the threshold-tracking method.
Significance:
Caffeinés effect may result from its modulation of the cholinergic system, providing insights into both its physiological action and brain disorder pathophysiology.
