Postsynaptically different inhibitory postsynaptic currents in Cajal-Retzius cells in the developing neocortex.

Fast and slowly rising inhibitory postsynaptic currents (IPSCs, IPSC F and IPSCs) in neocortical Cajal-Retzius cells are observed. In this study, zolpidem, a benzodiazepine agonist that specifically modulates γ-aminobutyric acid type A receptors (GABA A Rs) containing γ 2 subunit, was used to characterize GABA A RS mediating IPSC F and IPSCS. One-hundred-nanomolar zolpidem prolonged IPSC S , increased evoked IPSC S (elPSC s ) amplitude, and decreased paired-pulse ratio (PPR) of elPSCs. Two micromolar zolpidem prolonged both IPSC F and IPSC S , increased miniature IPSC F and elPSCp amplitudes, increased elPSCs amplitude but not miniature IPSCs amplitude, decreased PPR of elPSC s , but failed to affect PPR of elPSC F We conclude that IPSC F are mediated by α 2/3 -containing GABA A R S , which are not saturated by synaptic GABA release, whereas IPSCs are mediated by α 1 -containing and α 2/3 -containing GABA A R S , which are saturated by quantal GABA release.