Possible involvement of brain hydrogen sulphide in the inhibition of the rat micturition reflex induced by activation of brain alpha7 nicotinic acetylcholine receptors

We previously reported that brain α7 nicotinic acetylcholine receptors inhibited the rat micturition reflex. To elucidate the mechanisms underlying this inhibition, we focused on the relationship between α7 nicotinic acetylcholine receptors and hydrogen sulphide (H2S) because we found that H2S also inhibits the rat micturition reflex in the brain. Therefore, we investigated whether H2S is involved in the inhibition of the micturition reflex induced by the activation of α7 nicotinic acetylcholine receptors in the brain. Cystometry was performed in male Wistar rats under urethane anesthesia (0.8 g/kg, ip) to examine the effects of icv pre-treated GYY4137 (H2S donor, 1 or 3 nmol/rat) or aminooxyacetic acid (AOAA; non-selective H2S synthesis inhibitor, 3 or 10 μg/rat) on PHA568487 (α7 nicotinic acetylcholine receptor agonist, icv)-induced prolongation of intercontraction intervals. PHA568487 administration at a lower dose (0.3 nmol/rat, icv) had no significant effect on intercontraction intervals, while under pre-treatment with GYY4137 (3 nmol/rat icv), PHA568487 (0.3 nmol/rat, icv) significantly prolonged intercontraction intervals. PHA568487 at a higher dose (1 nmol/rat, icv) induced intercontraction interval prolongation, and the PHA568487-induced prolongation was significantly suppressed by AOAA (10 μg/rat, icv). The AOAA-induced suppression of the PHA568487-induced intercontraction interval prolongation was negated by supplementing H2S via GYY4137 at a lower dose (1 nmol/rat, icv) in the brain. GYY4137 or AOAA alone showed no significant effect on intercontraction intervals at each dose used in this study. These findings suggest a possible involvement of brain H2S in inhibiting the rat micturition reflex induced by activation of brain α7 nicotinic acetylcholine receptors.