Stress-induced thermoprotection of neuromuscular transmission.

Environmental stresses such as high temperature or low levels of oxygen can lead to structural destabilization of cells, disruption of cellular processes, and, in extreme cases, death. Previous experience of sub-lethal stress can lead to protection during a subsequent stress that may otherwise have been lethal. Synapses are particularly vulnerable to extreme environmental conditions and failure of function at this level may be the primary cause of organismal death. Prior heat shock induces enhanced thermotolerance at neuromuscular junctions in the locust extensor tibiae muscle and in abdominal muscles of larval Drosophila. Synaptic thermoprotection is associated with an increase in short-term plasticity at these synapses. Prior anoxic coma in locusts induces synaptic thermotolerance suggesting that the same protective pathways are activated. It is well established that diverse forms of stress induce the upregulation of cellular chaperones (heat shock proteins; HSPs) that mediate acquired protection. The mechanisms underlying HSP-mediated synaptic protection are currently unknown but evidence is accumulating that stabilization of the cytoskeleton may play an important role.