Neuroprotection at Drosophila synapses conferred by prior heat shock.

Synapses are critical sites of information transfer in the nervous system, and it is important that their functionality be maintained under stressful conditions to prevent communication breakdown. Here we show that synaptic transmission at the Drosophila larval neuromuscular junction is protected by prior exposure to heat shock that strongly induces expression of heat shock proteins, in particular hsp70. Using a macropatch electrode to record synaptic activity at individual, visualized boutons, we found that prior heat shock sustains synaptic performance at high test temperatures through pre- and postsynaptic alterations. After heat shock, nerve impulses release more quantal units at high temperatures and exhibit fewer failures of release (presynaptic modification), whereas the amplitude of quantal currents remains more constant than does that in nonheat-shocked controls (postsynaptic modification). The time course of these physiological changes is similar to that of elevated hsp70. Thus, stress-induced neuroprotective mechanisms maintain function at synapses by modifying their properties.