Long-term effects of prior heat shock on neuronal potassium currents recorded in a novel insect ganglion slice preparation

Brief exposure to high temperatures (heat shock) induces long-lasting adapt ive changes in the molecular biology of protein interactions and behavior o f poikilotherms. However, little is known about heat shock effects on neuro nal properties. To investigate how heat shock affects neuronal properties w e developed an insect ganglion slice from locusts. The functional integrity of neuronal circuits in slices was demonstrated by recordings from rhythmi cally active respiratory neurons and by the ability to induce rhythmic popu lation activity with octopamine. Under these "functional" in vitro conditio ns we recorded outward potassium currents from neurons of the ventral midli ne of the Al metathoracic neuromere. In control neurons, voltage steps to 4 0 mV from a holding potential of -60 mV evoked in control neurons potassium currents with a peak current of 10.0 +/- 2.5 nA and a large steady state c urrent of 8.5 +/- 2.6 nA, which was still activated from a holding potentia l of -40 mV. After heat shock most of the outward current inactivated rapid ly (peak amplitude: 8.4 +/- 2.4 nA; steady state: 3.6 +/- 2.0 nA). This cur rent was inactivated at a holding potential of -40 mV. The response to temp erature changes was also significantly different. After changing the temper ature from 38 to 42 degrees C the amplitude of the peak and steady-state cu rrent was significantly lower in neurons obtained from heat-shocked animals than those obtained from controls. Our study indicates that not only heat shock can alter neuronal properties, but also that it is possible to invest igate ion currents in insect ganglion slices.