The effects of nitric oxide (NO) on inhibitory neurotransmitter receptors and some types of inhibitory receptors in dissociated rod bipolar cell (RBC) were investigated. In the whole cell voltage-clamping mode, the gamma-aminobutyric acid (GABA) activated current showed both sustained and transient components. GABA activated transient current was fully blocked by bicuculine, a GABA_A receptor antagonist. The cis-4-aminocrotonic acid (CACA), a GABA_C receptor agonist, evoked the sustained current that was not blocked by bicuculline (BIC). Glycine activated the transient current. These results indicate that the RBCs possess GABA_A, GABA_C, and glycine inhibitory receptors. Sodium nitroprusside (SNP), a NO analogue, reduced the currents activated by GABA_A receptor only, however, did not reduce the currents activated by either GABA_C or glycine receptors. This study signifies further that only NO depresses the fast inhibitory response activated by GABA_A receptor in RBC. We, therefore, postulate that NO might depress the light-on/off transient inhibitory responses in RBCs in the rat retina.

Keywords: Nitric oxide, Sodium nitroprusside, GABA receptor, Glycine receptor, Whole-cell Patch- Clamp, Rod bipolar cells, Retina