Burst discharges associated with phasic hyperpolarizing oscillations of rat ventrobasal relay neurons

Intracellular recordings were made from ventrobasal relay neurons in urethane-anesthetized rats. A series of phasic hyperpolarizations repeated with the spindle rhythm appeared in response to single shocks to the medial lemniscus or spontaneously. On the recovery slope of some phasic hyperpolarizations slow depolarizations (SDs) lasting for 30-50 ms with burst discharges were generated as rebound excitation. The voltage dependency of SDs was proved by changing the membrane potential by current injection. The number of spikes triggered by the SD increased as the SD became larger in amplitude and faster in rising speed.