MODIFICATION OF THE MECHANICAL THRESHOLD OF THE PACINIAN CORPUSCLE AFTER ITS PERFUSION WITH SOLUTIONS OF VARYING CATION CONTENT

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Abstract
Changes in the threshold of the Pacinian corpuscle for mechanical stimulation by perfusion with Na-free solution, Li solution and solutions of varying K and Ca concentrations respectively were measured. After perfusion of the corpuscle with Na-free solution the threshold increased 1st and the initiation of impulses was abolished within 8 min. after perfusion. The impulse reappeared immediately after replacing Na-free solution by the normal one, the threshold returning to the initial value within 3.6 min. Li solution caused an increase in the threshold and abolished the impulse within 22 min. after the onset of perfusion, the recovery time being about 30 min., while nerve fibers supplying corpuscles lost their excitability after 90 min. in Li solution. Perfusion with solutions of low K content and K-free solution produced a slight increase in the threshold, while with 11.2 mM KCl-solution the threshold was decreased. Perfusion with 28.4 mM KCl-solution caused a marked increase in the threshold and abolished the impulse. By perfusion with low Ca solution a threshold decrease was observed and with Ca-free solution the impulse initiation was maintained for 1 hr., while Ca-free solution containing EDTA blocked the impulse. Effects of EDTA were reversible. With increasing Ca concentration in the perfusing solution the threshold increased and in 108 mM Ca-solution the impulse initiation was abolished. Na and Li ions are mainly responsible for the generation of the receptor potential but Ca and K ions may not affect the receptor potential directly.