Effects of Single Pinna Reflex and Dynamic Stretch on Spike Discharges of Caudate Muscle Spindle Nerves in Rat

Introduction: The γd motor axons that innervate the muscle spindle fibers couldinduce the excitation of spindle nerves. The purpose of this study was comparing thequality effects of pinna reflex (PR) and dynamic stretch (DS) on the discharges andamplitudes of spike potentials (SPs) of spindle Ia, II, and γd axons in rat.Methods and Materials : The experimental study on the SPs discharges of 45 singlecaudate muscle spindle afferents and γd axons from the left side L5 roots wererecorded at rest and during testing15 adult normal rats by PR and by DS. Thecomparison among the means SPs amplitudes of Ia, II, and γd axons in the restingdischarge (RD) and after applying the PR and the DS were investigated by measuringtheir amplitudes.Results: The SPs amplitudes of Ia (72±5.34μv), II (38±3.27μv), and d (62±4.29 μv)were calculated in the RD. The obtained mean SPs amplitude difference was21% forIa and7.7% for II; in the DS more than in the PR. The SPs of Ia and II made someoverlaps by using the two stimula. The γd SPs followed the SPs of Ia and II duringthe PR whereas this case didn’t occur for the spindle axons during the DS. The mean SPs amplitude difference of d in the DS was 85% less than in the PR.Conclusion: The DS (independent to γd SPs) was as distinctive stimulus for excitingof single Ia and II fibers as the PR (dependent to γd SPs). The γd showed stronginactivity by the DS. These results would be playing role in controling the movementdisorders.