Inhibition of canine H reflexes during locomotor-like rotation about the
knee arises from muscle mechanoreceptors in quadriceps.
Misiaszek, John E., Jack K. Barclay, and John D. Brooke.
Biophysics Interdepartmental Group and School of Human Biology, University
of Guelph, Guelph, Ontario, Canada N1G 2W1.
APStracts 2:0032N, 1995.
SUMMARY AND CONCLUSIONS
1. H reflexes were elicited in the small muscles of the foot in the canine
and human during passive locomotor-like rotation of the shank about the
ipsilateral knee. The movement-induced effect was similar in the two species.
In the anaesthetized dog, the reflex gain was reduced by 36 + 8.4% on
average, compared to appropriate stationary controls. Reflexes in the human
were reduced during movement to 45 + 3.5% of their stationary control
values. 2. H reflexes were elicited in the anaesthetized dog during passive
locomotor-like rotation about the knee and were compared to reflexes obtained
with the limb stationary. Populations of mechanoreceptors were then
systematically removed to ascertain which group or groups provided the sensory
input that leads to the decrease in reflex gain during movement. We
hypothesized that the majority of the reflex attenuation could be attributed
to muscle mechanoreceptors. 3. Reflexes continued to be significantly reduced
(p<0.05) during passive movement about the knee until the muscle
mechanoreceptors of the quadriceps muscle group were deactivated. The removal
of input from joint receptors or cutaneous receptors did not eliminate the
gain reduction induced by the passive movement. 4. It is concluded that
muscle mechanoreceptors of the quadriceps muscle group provide an inhibitory
input to the H reflex pathway of the dog plantar muscle when the knee is
passively moved in a locomotor-like fashion. This source of inhibition likely
also contributes to the soleus H reflex gain reduction in humans.
Received 10 November 1994; accepted in final form 9 February 1995.
APS Manuscript Number J713-4.
Article publication pending J. Neurophysiol.
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 3 April 1995.