Responses of nucleus z neurons to vibration of hindlimb extensor muscles in the decerebrate cat.

1. Small sinusoidal changes of length, applied longitudinally to the ddifferented GS muscle, were uused as a specific stimulus to activate the muscle spindle receptors in precollicular decerebrate cats. In order to determine the relative contribution of the primary and secondary endings of muscle spindles to the response of the nucleus z neurons, the effects of muscle vibration on this unit activity were studied under conditions in which the segmental monosynaptic reflexes produced by stimulation of the primary endings of muscle spindles were continuously monitored. 2. Vibration of the GS muscle (at 180-200/sec and amplitudes up to 250-320 mu) affected the frequency and pattern of discharge in 50 out of 168 units recorded from the lower medulla...