Electrophysiological study of formation of new synapses and collateral sprouting in red nucleus neurons after partial denervation.

Intracellular recording was made from cat's red nucleus after chronic lesion of the nucleus interpositus (IP) of the cerebellum and the properties of the corticorubral EPSPs were examined. 2. It was found that the time to peak of the corticorubral ESPSs induced from cerebral peduncle (CP EPSP) of chronic cats was much faster than that of normal cats. There was no simple decay following the rapid rise and early summit; instead there was another peak as if the slow normal CP EPSPs were superimposed on the fast ones. 3. By stimulating two loci, sensorimotor cortex and the cerebral peduncle, the conduction velocities of the fibers responsible for the newly appeared fast-rising component of the corticorubral EPSPs were measured. They were almost the same as those of normal corticorubral EPSPs.