The effects of temperature on locust ocellar L-neurones and their interconnections

The effects of temperature, over the range 10–40 °C, on properties of locust (Schistocerca gregaria) ocellar L-neurones and of their interconnections have been investigated. At cooler temperatures, a small change in temperature has a larger effect than an equivalent change at warmer temperatures. An increase in temperature leads to the following:

1.	A decrease in input resistance, which typically halves in value as temperature increases from 15 °C to 35 °C. When synaptic transmission between photoreceptor cells and L-neurones is blocked with cobalt, temperature still affects L-neurone resistance. The membrane time constant also decreases, but the resting potential is unaffected.
2.	An increase in the sizes of rebound spikes, which are produced when hyperpolarizing pulses end. Above 35 °C, the maximum size of rebound spike is smaller than that at cooler temperatures.
3.	A decrease in the latency to response to light, and an increase in the speeds of the transient responses to changes in light.
4.	A decrease in the latency of transmission at both excitatory and inhibitory synapses between L-neurones.
5.	At excitatory synapses between L-neurones, an increase in the postsynaptic current. This is compensated by a decrease in postsynaptic membrane resistance, so that there is little effect on the size of the postsynaptic potential.
6.	At inhibitory synapses between L-neurones, a decrease in the time for the postsynaptic potential to reach its peak. The time for recovery of transmission at inhibitory synapses is unaffected by temperature.