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Journal of Experimental Biology 117,369-388 (1985)
Published by Company of Biologists 1985

Temperature Acclimation: Influence on Transient Outward and Inward Currents in an Identified Neurone of Helix Pomatia

DEJAN ZECEVIC 1, HERBERT LEVITAN 2, and MIRA PASIC 3

1 Institute for Biological Research, University of Belgrade, 142, Belgrade, Yugoslavia; Yale University School of Medicine, Department of Physiology, 333 Cedar Street, New Haven, CT 06510, U.S.A
2 Department of Zoology, University of Maryland College Park, Maryland, U.S.A
3 Institute for Biological Research, University of Belgrade 29 November 142, Belgrade, Yugoslavia

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 steady-state inactivation parameters of the A-current (Bo), nor the ratio of the time constants of A-current activation and inactivation ({tau}A/{tau}B) 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{infty}).

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.

Key words: temperature acclimation, molluscan neurone, voltage-clamp

Accepted on December 20, 1984






© The Company of Biologists Ltd 1985