In vitro contractile responses of detrusor to carbachol and neurokinin A, in children with recurrent urinary tract infection or day wetting

To investigate whether a history of recurrent urinary tract infection (UTI) and/or the presence of day-wetting/urge symptoms might influence the contractile responses to the cholinergic agonist carbachol or to the sensory neuropeptide neurokinin A (NKA) in the urinary bladder in children.Small detrusor strips were taken from the margin of the cystotomy incision of the bladder dome during surgery to correct vesico-ureteric reflux (VUR) in 62 children (aged 4 months to 12 years) or for unrelated bladder conditions in five controls (aged 3 months to 13 years). Concentration-response curves to carbachol and NKA were constructed using organ-bath techniques, and results compared for age, sex, weight of the detrusor strip, UTI history or day-wetting syndrome.The contractile responses to NKA were no different for any of the features investigated. The contractile response to carbachol and NKA in detrusor from control and VUR patients was not significantly different. The children with a history of UTI were significantly older than those without. The contractility in response to carbachol was greater in older girls (aged 4-12 years) than younger girls (4 years) and than in all boys (4 years and 4-12 years; ANOVA P = 0.013). The mean (SEM) maximum contractile response to carbachol in the group of 20 young children (4-30 months) with previous UTI was 3.0 (0.3) g, whereas the maximum response in the age-matched group of 11 without UTI was 1.8 (0.3) g (P = 0.046). There were no significant differences in maximum responses between those with day-wetting and those without (aged4 years), although there was a significant difference in pD2 value, at 6.19 (0.13) and 5.58 (0.14), respectively (P = 0.018).Carbachol produced a larger contractile response in detrusor from children with a history of UTI than from those without, indicating possible alterations in muscarinic receptor characteristics. An increased sensitivity to muscarinic stimulation in day-wetting children was also suggested, whereas NKA is unlikely to be involved in any of these pathophysiological conditions.