The action of piperidine on muscle spindles in the rat.

Piperidine hydrochloride induced discharge in primary and secondary endings of muscle spindles in rat tailbase muscle preparations. The threshold concentration for primary endings (2.0 X 10(-5) g/ml) was below that for secondary endings (4.0 X 10(-5) g/ml). The effect of piperidine was antagonised by tubocurarine but not by atropine. The action of piperidine on primary and secondary endings responding to 'ramp-and-hold' stretch was predominantly on the static component of excitation, and usually in the absence of any concomitant enhancement of the dynamic effect. This effect was opposite to that induced by succinylcholine. A possible action of piperidine at cholinoceptive sites of the nicotinic type and associated with gamma-trial fusimotor terminals is discussed.