Specificity of neuronal responses evoked in the medial geniculate body by stimulation of its different main inputs:In vivo andin vitro investigations

Responses evoked in single neurons of the medial geniculate body (MGB) by electrical stimulation of auditory cortex and fibers of the brachium of the inferior colliculus (BIC) were investigated in vivo and in vitro. In vivo experiments were performed on cats anaesthetized by kalipsol. In vitro experiments were carried out on surviving slices of the rat brain using MGB intranuclear simulation. It has been found that the responses to cortical and nuclear local stimulations show similar peculiarity: an increase in stimulation rate is followed by potentiation and summation of slow EPSPs. At the same time, BIC stimulation evokes mainly fast EPSPs (both in vivo and in vitro) which are remarkably suppressed when rate and intensity of BIC stimulation increase. Distinct features of the MGB neuronal responses to activation of ascending pathways and corticofugal fibers are probably due to differences in anatomical structural among the tested inputs and in chemical mechanisms of the synaptic processes.Neirofiziologiya/Neurophysiology, Vol. 25, No. 3, pp. 203–211, May–June, 1993.