The whole-cell configuration of the patch-clamp technique was used to analyse currents induced by glycine in chick ciliary ganglion neurons freshly dissociated from 14- to 15-day-old embryos. 2. Application of glycine to cells voltage-clamped at -60 mV induced inward currents in all neurons tested. Dose-response curves yielded an EC50 of about 50 microM. Similar responses were elicited by beta-alanine and taurine though higher concentrations were required. 3. Strychnine reversibly inhibited the glycine-induced responses. The effect was dose dependent with a half-maximal effect being obtained with 20 nM strychnine. 4. Glycine-induced currents were inhibited by 100 microM Zn2+. The inhibition had slow rates of onset and recovery, in contrast to Zn2+ inhibition of GABA responses. Both bicuculline and d-tubocurarine inhibited glycine responses in a dose-dependent manner. 5. The steady-state I-V curve for glycine-induced currents was linear over the range -60 to +60 mV, but showed an outward rectification at very hyperpolarized membrane potentials. The reversal potential of glycine-induced currents shifted with changes in intracellular chloride concentration in a manner expected for chloride-selective channels. 6. Expression of functional glycine receptors during development was examined at embryonic day 8 (E8), 11, 14, and 18. The mean peak current was about 60-fold larger at E14 than at E8 and vastly exceeded changes in cell size. During the same period, responses to GABA increased only 2-fold in amplitude and correlated with changes in cell size.(ABSTRACT TRUNCATED AT 250 WORDS)
