Cholinergic nitric oxide release from the urinary bladder mucosa in cyclophosphamide-induced cystitis of the anaesthetized rat

Background and purpose: Previous reports have suggested that nitric oxide ( NO) may be released by cholinergic stimuli in the rat bladder in cyclophosphamide-induced cystitis, affecting bladder function. In the current study, we evaluated the effects of cyclophosphamide-induced cystitis on muscarinic whole bladder contractile responses in vivo, and further, if NO might be released from the mucosa by cholinergic stimuli. Experimental approach: Male rats were pre-treated either with cyclophosphamide ( 100 mg kg(-1); to induce cystitis) or saline ( serving as controls). 60 h later, rats were anaesthetized and bladder pressure monitored. Key results: The muscarinic receptor agonist methacholine ( MeCh; 0.5 - 5 mu g kg(-1) i.v.)induced similar contractions ( i.e. bladder pressure increases) in inflamed bladders as in controls, which were attenuated dose-dependently by the muscarinic M-1/M-3/M-5 antagonist 4-diphenylacetoxy-N-methylpiperidine(4- DAMP; 0.1-1000 mu g kg(-1) i.v.). In inflamed bladders, the cholinergic bladder contractions were enhanced after removing the mucosa, while cholinergic contractions were similar in intact and urothelium-denuded inflamed bladders in the presence of the NO synthase inhibitor No-nitro-L-arginine methyl ester ( L-NAME; 30 mg kg(-1) i.v.). L-NAME attenuated the antagonistic effect of 4- DAMP on MeCh-induced contractions in intact inflamed bladders. However L-NAME did not affect the antagonism by 4- DAMP of MeCh-induced contractions of urothelium-denuded bladders, under control conditions or with cyclophosphamide-induced cystitis. Conclusions and implications: In cyclophosphamide-induced cystitis, the cholinergic function of the bladder is altered. In the inflamed bladder, NO seems to be released via cholinergic stimuli through mucosal muscarinic M-3/M-5 receptors, presumably on urothelial cells, affecting bladder function.