Summary
The surface ofStylonychia was mechanically stimulated with a piezo-crystal driven microneedle of 0.5-2 μm distal diameter and maximal amplitudes of 13 μm. Stimulation of the anterior surface of the cell produced a membrane depolarization, while stimulation of the posterior surface elicited a hyperpolarizing response. The analysis of electric responses to mechanical stimuli, driven by pulses varied in duration, amplitude, rate and acceleration, revealed that the hyperpolarizing receptor potential (hRP) rose in parallel with the stimulus velocity. Stimulus amplitudes beyond 12 μm and at rates larger than 4 mm/s did not increase the amplitude of the membrane response. Sustained stimuli slowed down the repolarization to the resting level. Adaptation of the receptor response was seen with small and sustained velocities of the stimulating probe. The depolarizing receptor response (dRP) triggered an action potential consisting of two regenerative components, one graded, the other all-or-none. Positive conditioning current pulses reversed the polarity of the dRP which was primarily Ca-dependent (22.4 mV/log [Ca]0).
The dRP was isolated from the action potential by negative membrane conditioning. The reversal potential of the hyperpolarizing receptor response was negative of the resting potential and completely K-dependent (58.5 mV/log [K]o).
Submaximal hyperpolarizing and subthreshold depolarizing receptor potentials showed summation. No refractoriness of the hRP was detected. Summation of depolarizing responses beyond the threshold activated a regenerative membrane depolarization.
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Abbreviations
- hRP:
-
Hyperpolarizing receptor potential
- dRP:
-
Depolarizing receptor potential
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Dedicated to Professor J. Schwartzkopff on the occasion of his sixtieth birthday
Supported by the Deutsche Forschungsgemeinschaft (SFB 114, TP A5)
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de Peyer, J.E., Machemer, H. Hyperpolarizing and depolarizing mechanoreceptor potentials inStylonychia . J. Comp. Physiol. 127, 255–266 (1978). https://doi.org/10.1007/BF01350116
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DOI: https://doi.org/10.1007/BF01350116