Temperature compensation in the peripheral nervous system: Antarctic vs temperate poikilotherms

Abstract

The effects of temperature on compound action potential velocities in peripheral nerves from antarctic fishes and invertebrates were compared with those from temperate poikilotherms. Conduction velocity is a linear function of temperature, with sharp upper and lower limits corresponding to ‘heat-block’ and ‘cold-block’. Slope, x-intercept and cold- and heat-block temperatures were reduced in antarctic poikilotherms. Cold-block could not be demonstrated, but heat-block occurred around 31 °C. Neuromuscular activation failed between 16 ° and 22 °C in antarctic preparations. Fast fibres show steeperV/T slopes than slow fibres, but the two classes tend to converge on a common x-intercept; normalised velocities give nearly identical slopes, indicating that both large and small fibres are affected equally by temperature. Similarities in pattern between shortand long-term cold adaptation in both poikilotherms and endotherms suggest a common mechanism for membrane adaptations to low temperatures, and are consistent with the hypothesis of homeoviscous adaptation.