Electrophysilogical study of synaptic transmission in inferior olivary neurons of postnatal rats

Abstract

Inferior olive (IO), projecting contralaterally to Purkinje cells in the cerebellar cortex via climbing fibers, has been known to play an important role in motor coordination. However, the nature of the excitatory and inhibitory inputs that modulate the properties of IO neurons during postnatal development remains unexplored. Whole-cell patch-clamp experiments were performed in brainstem slices of postnatal rats to investigate the developmental profile of glutamate receptor-mediated excitatory transmission and γ-aminobutyric acid receptor-mediated inhibitory transmission in IO neurons. Miniature-excitatory postsynaptic currents (mEPSCs) were recorded in IO neurons of P1, P4, P7, P14 and P21 rats. The amplitude of mEPSCs in P14 rats was significantly greater than those of other age groups. The decay time increased while the rise time decreased with maturation. There was no change in the frequency of EPSCs during development. We also recorded miniature-inhibitory postsynaptic currents (mIPSCs) in developing IO neurons. The amplitude of mIPSCs in P7 rats was significantly greater than those of other age groups. The decay time decreased until P7 while there was no change in the rise time with maturation.. The frequency, however, increased, reaching a plateau at P4. Taken together, our findings document progressive maturation of excitatory and inhibitory synaptic transmission in rat IO neurons.