Heat shock-induced thermoprotection of action potentials in the locust flight system

There is increasing evidence that heat shock (HS) has long-term effects on electrophysiological properties of neurons and synapses. Prior HS protects neural circuitry from a subsequent heat stress but little is known about th e mechanisms that mediate this plasticity and induce thermotolerance. Expos ure of Locusta migratoria to HS conditions of 45 degreesC for 3 h results i n thermotolerance to hitherto lethal temperatures. Locust flight motor patt erns were recorded during tethered flight at room temperature, before and a fter HS. In addition, intracellular action potentials (APs) were recorded f rom control and HS motoneurons in a semi-intact preparation during a heat s tress. HS did not alter the timing of representative depressor or elevator muscle activity, nor did it affect the ability of the locust to generate a steering motor pattern in response to a stimulus. However, HS did increase the duration of APs recorded from neuropil segments of depressor motoneuron s. Increases in AP duration were associated with protection of AP generatio n against failure at subsequent elevated temperatures. Failure of AP genera tion at high temperatures was preceded by a concomitant burst of APs and de polarization of the membrane. The protective effects of HS were mimicked by pharmacological blockade of IK+ with tetraethylammonium (TEA). Taken toget her, these findings are consistent with a hypothesis that HS protects neuro nal survival and function via K+ channel modulation. (C) 2001 John Wiley & Sons. Inc.