THE INFLUENCE OF AGE ON ISOMETRIC AND ISOTONIC RAT DETRUSOR CONTRACTIONS

Background. Reductions in detrusor shortening velocity and detrusor co ntractility have been observed in association with aging. The reasons for these changes are unclear. Methods. We examined the isometric and isotonic responses of detrusor, taken from the bladder body, to adenos ine 5'-triphosphate (ATP), noradrenaline (NA), serotonin, and acetylch oline (Ach) in vitro, using bladders from young (30 days) and old (365 days) Sprague Dawley rats, to determine whether there were any signif icant age-related differences. Results. Isometric contractions with AT P at doses of 10(-3) to 10(-2) molar concentrations produced greater c ontractile forces in old rats when compared to young rats (p = .0136 a t 10(-2) mole of ATP). Isotonic contractions at similar concentrations also produced significant differences between the young and the old r ats, the latter being faster (p = .0225). Isometric contraction with n oradrenaline produced significant differences between young and old ra ts, the latter being stronger. This became apparent at 10(-4) molar co ncentration of noradrenaline (p = .0043). Isometric contractions with serotonin also produced significantly greater contractions in the old rats when compared to young rats. The differences became apparent at 1 0(-4) molar concentration of serotonin (p = .045). There were no age-r elated differences in isotonic and isometric contractile responses to acetylcholine in the doses used in our experimental setup. Conclusions . Age-related differences in isometric function were detected in respo nse to ATP, NA, and serotonin. Differences in isotonic function were o nly found in response to ATP and Ach.