Prepulse modulation and recovery of trigemino-cervical reflex in normal subjects.

Abstract

In this study, we analyzed the inhibitory control on the trigemino-cervical reflex (TCR), and whether or not prepulse modulation (PPM) has an effect on TCR. Thus, we studied the PPM of TCR. We hypothesized that TCR would presumably be under the modulatory effect after the prepulse stimulus similar to blink reflex (BR). We also studied the recovery of TCR which was previously shown. We included 13 healthy individuals. All subjects underwent recordings of TCR, TCR-PPM, and recovery of TCR. For TCR-PPM, a subthreshold stimulus to second finger 50 or 100ms before the test stimulus was applied. For recovery of TCR, two stimuli at the infraorbital nerve were applied at 300, 500, and 800ms interstimulus intervals (ISIs). There was an inhibition of bilateral late responses of TCR at the ISIs of both 50ms and 100ms. There was no change of latencies. Full recovery of TCR did not develop even at the ISI 800ms. We have provided an evidence for the TCR-PPM in healthy subjects for the first time in this study. The prepulse inhibition is attributed to the functions of the pedunculopontine tegmental nucleus. Our study provides a strong indication that there are connections between pedunculopontine tegmental nucleus and trigemino-cervical circuit, which produces TCR.