Neurophysiological Studies of Harmaline-Induced Tremor in the Cat

Abstract

Harmaline induces in the cat a generalized tremor, synchronous in all muscles, at a frequency of 8–12/s. This tremor has a central origin since motoneuronal rhythmic firing persists after paralysis or deafferentation. Intracellular recordings of lumbar motoneurons reveal spontaneous rhythmic EPSPs under harmaline; this rhythmic activity is not reset by antidromic stimulation. The cerebellum and the lower brain stem reticular formation appear to be primarily involved in the elaboration of supraspinal tremorogenic impulses, which are transmitted to segmental level by crossed and uncrossed reticulospinal fibers coursing on either side in the ventral half of the spinal cord.