Inferior olive destruction induces dysfacilitation of the red nucleus activity

The spontaneous discharge frequency of the red nucleus neurones was evaluated in rat before and after total destruction of the inferior olive with the 3-acetylpyridine. It was found that the sustained firing recorded in the control animals (33.7 +/- 23.7/s) drastically decreased to a low rate (4.6 +/- 7.1/s) after the intoxication. This effect took place between 2 h 15 min and 2 h 45 min after the injection. which is the critical period corresponding to the inferior olive degeneration and the consequent climbing fiber deafferentation. It lasted at least as long as the acute experiment. The conclusions are reached that the inferior olive destruction leading to an enhanced cerebellar inhibition, produces a dysfacilitatory effect on the red nucleus neurones.