Membrane potential depolarization in the porcine ciliary epithelium evokedby nitric oxide

Background: The present work studies if in porcine ciliary body epithelium the intracellular signal transduction pathway nitric oxide (NO)-guanylate c yclase (GC)-3',5'-cyclic guanosinemonophosphate (cGMP) can change the membr ane potential of the epithelium of the ciliary body. Material and Methods: Recordings of membrane potentials were done by means of intracellular microelectrodes in the presence of the NO donor Sodium Nit roprusside (SNP; 100 mu M; n = 5) or the membrane permeable cGMP analogue 8 -parachlorophenyl-thioguanosine-3',5' cyclic monophosphate (8-pCPT-cGMP; 10 0 mu M; n = 5). To test whether the GC is involved in this process, recordi ngs were repeated in both groups in presence or in absence of the GC inhibi tor 1-H-(1,2,4)oxadiazole-(4,3-a)quinoxalin-1-one (ODQ; 10 mu M; n = 4). Results: SNP and 8-pCPT-cGMP both induced significant membrane potential de polarizations (7.7 +/- 1.8 mV and 13.1 +/- 1.3 mV, mean +/- SEM). Membrane depolarizations induced by SNP were significantly inhibited by ODQ (p < 0.0 1), whereas depolarizations induced by 8-pCPT-cGMP were not altered by the presence of ODQ (p > 0.2). Conclusions: Nitric oxide induces depolarizations of the membrane potential in the isolated porcine ciliary body. This process is transduced by activa tion of the GC. We conclude that nitric oxide might be involved in the regu lation of permeability of the cellular membrane for ions in the ciliary bod y.