EFFECTS OF HEAT-STRESS ON AXONAL CONDUCTION IN THE LOCUST FLIGHT SYSTEM

Pretreatment of tissues or whole organisms with high, sublethal temper atures (heat shock) induces thermotolerance to normally lethal tempera tures. It is of interest whether heat shock induces protection of neur onal function at normally lethal temperatures by investigating effects of heat shock on the temperature sensitivity of neuronal parameters i n the locust flight system. The rhythm frequency of the deafferented f light motor was measured as well as the conduction velocity and amplit ude of extracellularly recorded action potentials conveyed along the f orewing stretch receptor axon. Measurements were made at temperatures ranging from 10 to 50 degrees C in heat shocked and control animals. T he deafferented rhythm was less sensitive to temperature changes above 35 degrees C in heat shocked animals. The conduction velocity and rel ative amplitude of action potentials conveyed along the stretch recept or axon were less sensitive to temperature increases above 20 degrees C in heat shocked animals. These data suggest that heat shock conserve s 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 interactio ns and thus allow the circuitry to operate within optimal parameters. (C) 1998 Elsevier Science Inc. All rights reserved.