S-nitrosoglutathione (GSNO) has previously been shown to have a role in ultraviolet (UV) light-elicited relaxations and proposed to account for the photosensitive store in the mouse gastric fundus. Furthermore, the depletion of this photosensitive store and its replenishment via long-term electrical field stimulation were demonstrated in the same tissue. In relation to these results, the aim of the present study was to investigate the putative role of S-nitrosothiols in the restorative effect of long-term electrical field stimulation on the reduced photosensitive store. Two series of UV light-elicited relaxations (photorelaxations) were obtained, and the magnitudes of the responses were 53 +/- 6 and 26 +/- 3%, respectively. The second series of photorelaxations attenuated statistically when compared with those in the first series. Ethacrynic acid (1 mu M), diamide (1 mu M) and glutathione (1 mu M) had no effect on the photorelaxations occurred in the second series of responses. Electrical field stimulation (4 Hz, 25 V, 1 ms, 60 min), applied between two series of photorelaxations, revealed a complete recovery of the attenuated photorelaxations appeared in the second series. N-G-monomethyl-L-arginine (100 mu M), ethacrynic acid (1 mu M) and diamide (1 mu M) extensively prevented the restorative effect of electrical field stimulation on photorelaxations. In addition, glutathione (1 mu M) reversed the prevention achieved by ethacrynic acid and diamide. The conclusion is that the restoration accomplished by electrical field stimulation is because of the activation of nitric oxide synthase, which in turn brings about the regeneration of GSNO proposed to be the photodegradable material store.