Electrophysiological properties of the isolated vestibulocerebellar complex of the frog in vitro.

Parameters of the electrical activity of the isolated vestibulocerebellar complex of the frog were studied under in vitro conditions. In the region of the vestibular nucleus (nc. VIII), in the presence of stimulation of the stato-acoustic nerve (n. VIII), responses from efferent vestibular neurones and from unidentified (probably vestibulospinal) neurones were recorded. The latent periods of their excitatory postsynaptic potentials (EPSPs, 1.4-2.2 ms) were indicative of mono- and disynaptic connection. Inhibitory postsynaptic potentials (IPSPs) were also observed. Stimulation of the auricular lobe of the cerebellum evoked monosynaptic IPSPs, an EPSP-IPSP complex or pure EPSPs in nc. VIII, the latter probably by way of collaterals to the cerebellum. The inhibitory character of the effect of efferents from the cerebellum to the neurones of nc. VIII was demonstrated in the focal synaptic potential and in spontaneous and evoked unit activity. If n. VIII was stimulated, both focal and unit extra- and intracellular responses characteristic of activation of the Purkinje cells by mossy (MF) or climbing (CF) afferent fibres were recorded in the cerebellar cortex. The electrophysiological picture indicates that both synaptic transmission and the functional manifestations of the individual neurones are preserved in the tested preparation.