1. To gain insight into the mechanisms underlying compensatory changes in excitability induced by thermal acclimation we examined the effects of short-term and long-term temperature transition on a transient outward potassium current (A-current) and the transient inward current in an identified neurone (Br) of the land snail Helix pomatia.

  2. The A-current in neurones from snails acclimated to 20°C was suppressed by cooling to 3°C, with a Q10 of 4.5 between 10°C and 20°C. This is consistent with suppression of the ability of these neurones to fire repetitively at low temperatures.

  3. Neurones acclimated to low temperature (5°C) partially recovered their ability to fire repetitively, but exhibited no A-current, at this temperature.

  4. Neither the equilibrium potential for the A-current (EA), the steadystate inactivation parameters of the A-current (Bo), nor the ratio of the time constants of A-current activation and inactivation (τA/τB) were affected by cooling, leading to the conclusion that the reduction of the A-current by cooling was due to a decrease in the A-current activation parameters (GAA∞).

  5. Cooling reduced the maximum peak inward current, with a Q10 of 2, in neurones from warm-acclimated animals. After acclimation to 5°C, maximum peak inward current partially recovered.

  6. Cooling neurones from warm-acclimated animals slowed the time course of the recovery of inward current from inactivation. Acclimation to the cold caused a partial, compensatory shortening of the inactivation removal process.

Keywords:
temperature acclimation, molluscan neurone, voltage-clamp
© 1985 by Company of Biologists
1985
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