Spike activity of fastigial cerebellar neurons in rat: Effects of stimulation of thelocus Coeruleus andn. raphe pontis

Effects of electrical stimulation of the brain stem aminergic structures,locus coeruleus (LC) andn. raphe pontis (RP), on spike activity of neuronal units of then. fastigius (NF) of the rat cerebellum were studiedin vivo. A significant number ofNF neurons was found to respond to the activation of inputs from theLC andRP, showing no dependence on the localization of the units within theNF and the level of their background activity (BA). The responses of theNF neurons were predominantly selective, i.e., evoked by stimulation of only one of the inputs. Convergent effects of uniform or reciprocal pattern were found less frequently. The effects of stimulation were rather variable, but inhibitoryLC andRP influences dominated. TheLC effects appeared in a greater proportion ofNF neurons, and facilitatory influences from this structure were more usual. The pattern of responses toLC orRP stimulation was variable; monocomponent responses were more frequent, but there were also bi-, tri,- and polycomponent responses. High variability of their latent periods, duration, and intensity was found. Considering six main types of BA ofNF neurons classified earlier [1], we showed thatNF neurons with the longest cycles of BA variation (with significant correlation coefficients on the order of 20 to 40 of the compared interspike intervals), as well as the neurons with burst activity are most intensively affected by theLC. BurstingNF neurons responded more intensively toRP stimulation. Effects ofLC orRP stimulations depended on the BA level. Equal proportions of the neurons with low (<40/sec) BA frequency were inhibited and facilitated byLC stimulation. Inhibitory effects prevailed in the neurons with intermediate (40/sec to 70/sec) or high (>70/sec) BA frequencies.Neirofiziologiya/Neurophysiology, Vol. 25, No. 6, pp. 446–455, November–December, 1993.