STEP-LIKE SHIFTS OF MEMBRANE-POTENTIAL IN THE STRETCH RECEPTOR NEURON OF THE CRAYFISH (ASTACUS-FLUVIATILIS) AT HIGH-TEMPERATURES

1. The effects of temperatures between 10-32 °C on the slowly adapting stretch receptor neuron of the crayfish were studied with intracellular recording and potential clamp techniques. 2. The membrane potential was found to decrease about 0.3 mV/ °C with increasing temperature in the range of 10° to 30 °C. 3. At temperatures in the range of 25° to 32 °C stretch produced a brief intense impulse discharge followed by a maintained depolarization. A similar response could be elicited by intracellular cathodal pulses or appeared sometimes spontaneously. 4. Tetrodotoxin (TTX) at a concentration of 10-7-10-8 mg/ml completely abolished the plateau, the receptor potential remaining unaffected. 5. Lowering of Ca+ + concentration facilitated the development of the plateau while increase of Ca+ + concentration had the opposite effect. 6. At a resting potential of -68 mV and at +30 °C the pNa/pK was 0.03 using the Goldman equation, the PNa/PK at a plateau level of -35 mV being 0.18. -The time constant for the inactivation of the plateau response was in the order of 1 s. 7. The passive membrane conductance as measured with the potential clamp technique increased with increasing temperature. 8. The stretch induced current (SIC) decreased and the reversal potential (Erev) was shifted towards more positive values when temperature was raised. 9. It is suggested that the steplike shift of membrane potential at high temperatures may be attributed to an increase in PNa/PK of the regenerative portion of the membrane and that this increase as well as the increase in passive membrane conductance are accounted for by changes in the physical properties of the lipid phase of the membrane at high temperatures. © 1979 Springer-Verlag.