Hydrogen Sulfide Mediated Inhibitory Neurotransmission to the Pig Bladder Neck: Role of KATP Channels, Sensory Nerves and Calcium Signaling

Purpose: Because neuronal released endogenous H2S has a key role in relaxation of the bladder outflow region, we investigated the mechanisms involved in H2S dependent inhibitory neurotransmission to the pig bladder neck. Materials and Methods: Bladder neck strips were mounted in myographs for isometric force recording and simultaneous measurement of intracellular Ca2+ and tension. Results: On phenylephrine contracted preparations electrical field stimulation and the H2S donor GYY4137 evoked frequency and concentration dependent relaxation, which was reduced by desensitizing capsaicin sensitive primary afferents with capsaicin, and the blockade of adenosine 5'-triphosphate dependent K+ channels, cyclooxygenase and cyclooxygenase-1 with glibenclamide, indomethacin and SC560, respectively. Inhibition of vanilloid, transient receptor potential A1, transient receptor potential vanilloid 1, vasoactive intestinal peptide/pituitary adenylyl cyclase-activating polypeptide and calcitonin gene-related peptide receptors with capsazepine, HC030031, AMG9810, PACAP(6-38) and CGRP(8-37), respectively, also decreased electrical field stimulation and GYY4137 responses. H2S relaxation was not changed by guanylyl cyclase, protein kinase A, or Ca2+ activated or voltage gated K+ channel inhibitors. GYY4137 inhibited the contractions induced by phenylephrine and by K+ enriched (80 mM) physiological saline solution. To a lesser extent it decreased the phenylephrine and K+ induced increases in intracellular Ca2+. Conclusions: H2S produces pig bladder neck relaxation via activation of adenosine 5'-triphosphate dependent K+ channel and by smooth muscle intracellular Ca2+ desensitization dependent mechanisms. H2S also promotes the release of sensory neuropeptides and cyclooxygenase-1 pathway derived prostanoids from capsaicin sensitive primary afferents via transient receptor potential A1, transient receptor potential vanilloid 1 and/or related ion channel activation.