Structure of Neuronal Impulse Trains of the Rat Inferior Olive under Conditions of Long-Lasting Vibrational Influence

Abstract

In acute experiments on albino rats anesthetized with Nembutal (40 mg/kg, i.p.), we recorded the background impulse activity (BIA) generated by neurons of the inferior olive in the norm and after 5-, 10-, and 15-daylong vibrational influence (60 Hz, 2 h, daily). We characterized the distributions of neurons according to the regularity of impulse successions, their dynamics, and pattern of histograms of interspike intervals (ISIs); we also calculated the mean frequency of impulsation and the coefficient of variation of ISIs. It was demonstrated that the most significant shifts of the characteristics of BIA generated by neurons of the inferior olive were formed within the first 10 days of the vibrational influence. These shifts were observed mainly in the mean discharge frequency (increased within the initial period) and, to a lesser extent, in the intrinsic structure of impulse trains. Such shifts in the background activity of the inferior olive caused by long-lasting vibrational influence result, perhaps, from intensification of the influences of excitatory cerebellar/mesodiencephalic inputs to olivary neurons within the early periods of action of the above factor and prevalence of GABAergic influences within the later periods. It seems possible that, under such conditions, the characteristics of electrical synapses of the olivary neurons are also subjected to modification.