GABA release from cerebellar stellate cells is developmentally regulated by presynaptic GABA(B) receptors in a...

Transmitter release from boutons along a common axon is often regulated depending on the postsynaptic target. Here, GABA release from cerebellar stellate cells onto Purkinje cells and other stellate cells was examined in acute cerebellar slices of 2- and 4-week-old mice. Consistent with previous findings on action potential-dependent GABA release, we found a developmental decrease in inhibitory inputs onto Purkinje cells but not onto stellate cells when recording miniature inhibitory postsynaptic currents (mIPSCs). Although amplitudes of mIPSCs were developmentally reduced in both cell types, mIPSC frequencies were decreased in Purkinje cells but were increased in stellate cells. Similarly, modulation of GABA release by presynaptic GABA(B) receptors changed during development in Purkinje cells but not in stellate cells, as demonstrated by the baclofen-mediated depression of mIPSC frequency and evoked IPSC (eIPSC) amplitudes. The selectively diminished baclofen effect in 4-week-old Purkinje cells correlated with a selective downregulation of presynaptic GABA(B) receptors at stellate cell-to-Purkinje cell synapses observed by immunoelectron microscopy analysis. Thus, expression of GABA(B) receptors in stellate cell axons and presynaptic modulation of GABA release appear to change during development in a target-cell-specific manner.