RESPONSE OF THE NON-MYELINATED NERVE TERMINAL IN PACINIAN CORPUSCLES TO MECHANICAL AND ANTIDROMIC STIMULATION AND THE EFFECT OF PROCAINE, CHOLINE AND COOLING

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Abstract
1. Potential changes in response to antidromic and mechanical stimuli were recorded across an oil-saline interface placed close to or at the non-myelinated terminal of the Pacinian corpuscle, of which the lamellae had been removed up to the central core.2. An antidromic stimulus produced a diphasic potential indicating that an antidromic impulse can invade the terminal, while a mechanical stimulus generated a diphasic response of an all-or-nothing nature superimposed on a graded response, or on the receptor potential. This all-or-nothing response to mechanical stimuli can be abolished and the antidromic impulse becomes monophasic when procaine, choline or cooling is applied to the terminal.3. When a mechanical stimulus was delivered within a few msec after an antidromic impulse, the all-or-nothing response to mechanical stimuli was abolished, and only the receptor potential was observed during the refractory period of the terminal. The amplitude of the receptor potential became smaller as the interval between the mechanical and antidromic stimuli was shortened. The depression of the receptor potential could not be observed, when the terminal was made inexitable by procaine, choline and cooling so that antidromic impulses could not invade the terminal.4: The relative amplitude of the maximum receptor potential, the all-ornothing impulse at the terminal and the mechanically and antidromatically elicited impulses at the first node of Ranvier was measured; their average ratio being 0.49: 0.36: 0.85: 1.5. The receptor potential has a rise time of about 1 msec and the time constant of decay of its exponential falling phase is 0.9 msec, which is smaller than that obtained in intact Pacinian corpuscles.

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