Effect of a Blocker of Nicotine Acetylcholine Receptors on Excitatory Postsynaptic Currents in Ganglion Cells of the Rat Retina

Abstract

We examined the involvement of nicotine acetylcholine receptors (nAChRs) in the generation of background synaptic activity in rat retinal ganglion cells (RGCs). Experiments were carried out in vitro on RGCs of the isolated retina of 21-day-old rats using the patch-clamp technique in the whole cell configuration (voltage-clamp mode). The neurons did not undergo enzymatic processing in order to provide more adequate preservation of the properties of cells of the native retina. In 15 examined cells, the resting membrane potential (RMP) was –62 ± 2 mV, on average, the input resistance of the membrane was 573 ± 68 MΩ, and the membrane capacitance was 34 ± 5 pF. The effects of blocking of nAChRs were estimated using bеnzohexonium (BH) in a 450 μM concentration. Background excitatory postsynaptic currents (EPSCs) in RGCs appeared, under the conditions of our experiments, with the mean frequency of 3.1 ± 0.8 sec–1 (n = 10). Application of BH resulted in suppression of the currents in six cells. Significant selectivity of the effects of these blockers was observed; it affected mostly high-amplitude EPSCs (40–100 pA). The effect of BH was mostly reversible. Our results show that activation of nAChRs modulate electrical activity in RGCs; probably, these receptors mediate certain types of synaptic transmission. The general RGC population is rather heterogeneous from the aspect of the presence/absence of nAChRs and distribution of separate subtypes of the latter.