Heat shock-induced thermoprotection of hindleg motor control in the locust

Functional neuromuscular connections are critical for appropriate behaviour al responses, but can be negatively affected by increases in temperature. W e investigated the effects of heat shock on the thermosensitivity of a neur omuscular pathway to the hindleg tibial extensor muscle of Locusta migrator ia. We found that exposure to heat shock induced thermoprotection of both n euromuscular transmission and extensor muscle contraction by (i) increasing the upper temperature limit for failure, (ii) improving recovery following heat-induced failure and (iii) stabilizing excitatory junction potential a mplitude and duration rind extensor muscle contraction force at high temper atures, Furthermore, the heat-shock-induced thermoprotection of extensor mu scle contraction was not attributable to a protective effect on intrinsic c omponents of muscle contraction. Finally, the use of jumping as a locomotor strategy to avoid capture, a behavioural response dependent upon functiona lly competent neuromuscular connections at the hindleg tibial extensor musc le, became less sensitive to temperature following heat shock. We conclude that the natural stress response of the locust stabilizes neuromuscular sig nalling during temperature stress, and that this can underlie a thermoprote ction of muscle contraction force and thus alter the thermosensitivity of a n escape behaviour critical for survival.