Effects of heat stress on axonal conduction in the locust flight system

Abstract

Pretreatment of tissues or whole organisms with high, sublethal temperatures (heat shock) induces thermotolerance to normally lethal temperatures. It is of interest whether heat shock induces protection of neuronal function at normally lethal temperatures by investigating effects of heat shock on the temperature sensitivity of neuronal parameters in the locust flight system. The rhythm frequency of the deafferented flight motor was measured as well as the conduction velocity and amplitude of extracellularly recorded action potentials conveyed along the forewing stretch receptor axon. Measurements were made at temperatures ranging from 10 to 50°C in heat shocked and control animals. The deafferented rhythm was less sensitive to temperature changes above 35°C in heat shocked animals. The conduction velocity and relative amplitude of action potentials conveyed along the stretch receptor axon were less sensitive to temperature increases above 20°C in heat shocked animals. These data suggest that heat shock conserves the operation of the flight system at high temperatures. This may be accomplished by a decrease in the thermosensitivity of the conduction velocity and amplitude of action potentials within the central flight circuitry. The latter effect may serve to protect synaptic interactions and thus allow the circuitry to operate within optimal parameters.