Effect of temperature on postsynaptic potentials of cat spinal motoneurones.

The effect of spinal cord temperature on excitatory postsynaptic potentials (EPSP) and inhibitory postsynaptic potentials (IPSP) were measured by means of intracellular recordings from lumbar motoneurones of 43 cats. While body temperature and oil bath temperature were maintained between 37 and 38 degrees C, the temperature of the spinal segment under investigation was changed separately in the range between 30 and 42 degrees C. Cooling consistently produced an increase in amplitude and duration of both, mono- and poly-synaptic EPSPs and recurrent and direct IPSPs. Warming caused the opposite effect. The input resistance of the motoneurones was inversely related to the spinal cord temperature, while the latency of action potentials produced by intracellular injection of outward current was directly and exponentially related to spinal temperature. Although the data do not provide a quantitative differentiation of pre- versus postsynaptic temperature effects, they are consistent with the notion that temperature dependent changes on postsynaptic membrane properties contribute to the observed PSP changes. It is further suggested that similar postsynaptic temperature effects may be concerned in temperature sensitivity of proposed specific central neurones.