Depolarizing glycine responses in Cajal-Retzius cells of neonatal rat cerebral cortex

We investigated the properties of glycine-induced responses in Cajal-Retzius cells, a neuronal cell type essential for the establishment of neocortical larnination. Whole-cell and gramicidin-perforated patch-clamp recordings were performed on visually identified Cajal-Retzius cells in tangential slices from neonatal rat cortex (postnatal days 0-3). With a pipette Cl(-) concentration of 50 mM, bath application of 1 mM glycine induced a membrane depolarization of 32.8 +/- 7.4 mV and a massive decrease in membrane resistance by 88 +/- 1.4%. The membrane depolarization was abolished in the presence of the glycinergic antagonists strychnine (30 muM) and phenylbenzene-w-phosphono-alpha-amino acid (100 muM), while the GABA(A) receptor antagonist bicuculline (100 muM) and the glutamatergic antagonist (+/-)-2-amino-5-phosphonopentatonic acid (60 muM) were without effect, suggesting that the glycine-induced membrane responses were mediated exclusively by the strychnine-sensitive glycine receptor. The EC(50) for activation of glycine receptors was 0.54 mM, 1.62 mM and 2.41 mM, for the glycinergic agonists glycine beta-alanine and taurine, respectively. Since the reversal potential of the glycine-induced currents showed a strong dependency on the intracellular chloride concentration and was virtually unaffected under HCO(3)(-)-free conditions, the activation of glycine receptors was probably linked to Cl(-) fluxes with little contribution of HCO(3) ions. Perforated patch recordings from, Cajal-Retzius cells demonstrated that glycine elicited depolarizing responses mediated by Cl- currents which reversed at -41 +/- 3.7 mV. In summary, from these results we suggest that Cajal-Retzius cells of the neonatal rat cerebral cortex express functional strychnine-sensitive glycine receptors that mediate depolarizing membrane responses via Cl- efflux. (C) 2002 IBRO. Published by Elsevier Science Ltd. All rights reserved.