title: Changes in nerve-mediated contractility of the lower urinary tract in a mouse model of premature ageing.
abstract: OBJECTIVE
  A high incidence of lower urinary tract disorders is associated with ageing. In the senescent-accelerated prone (SAMP8) mouse strain and the senescent-accelerated resistant (SAMR1) strain, we compared smooth muscle contractility in responses to intrinsic neurotransmitters, both in the bladder and urethra.
  
  
  METHODS
  We analysed micturition frequency, the changes in muscle tension induced by electrical field stimulation or agonist administration, the density of nerves (adrenergic, cholinergic and nitrergic) and interstitial cells (ICs), as well as cGMP accumulation in bladder and urethral preparations.
  
  
  RESULTS
  Senescent mice of the SAMP8 strain displayed increased micturition frequency and excitatory contractility of neurogenic origin in the bladder. While cholinergic nerve density remained unchanged, there was a mild sensitization to ACh in male mice. Potentiation in the detrusor may be also provoked by the stronger contribution of ATP, together with reduced adrenergic innervation in males and COX-derived prostanoid production in females. The greater excitatory contractility in the urethra was probably due to the sensitization to noradrenaline, in conjunction with attenuated nitrergic relaxation. There were also fewer neuronal NOS immunoreactive (ir) nerves and vimentin-positive ICs, although the sildenafil- and diethylamine-NONOate-induced relaxations and cGMP-ir remained unchanged.
  
  
  CONCLUSIONS
  Premature senescent mice exhibit bladder and urethral hyperexcitability, coupled with reduced urethral relaxation of neurogenic origin, which could model the impaired urinary function in elderly humans. We propose that senescence-accelerated mice provide a useful tool to analyse the basic mechanisms of age-related changes in bladder and urethral function.
authors.affiliation: Department of Physiology, Veterinary School, Complutense University, Madrid, Spain.
authors.forename: D
authors.initials: D
authors.lastname: Triguero
authors.forename: A
authors.initials: A
authors.lastname: Lafuente-Sanchis
authors.forename: A
authors.initials: A
authors.lastname: Garcia-Pascual
mesh_terms: D000367:Age Factors; D000375:Aging / Q000235:genetics; D019588:Aging, Premature / Q000235:genetics / Q000503:physiopathology*; D000818:Animals; D004305:Dose-Response Relationship, Drug; D004558:Electric Stimulation; D005260:Female; D008297:Male; D051379:Mice; D023421:Models, Animal; D009119:Muscle Contraction / Q000187:drug effects; D009130:Muscle, Smooth / Q000187:drug effects / Q000294:innervation*; D018377:Neurotransmitter Agents / Q000494:pharmacology; D014521:Urethra / Q000187:drug effects / Q000294:innervation*; D001743:Urinary Bladder / Q000187:drug effects / Q000294:innervation*; D014554:Urination
chemical_list: D018377:Neurotransmitter Agents
keywords: SAMP8 mouse; adrenergic; ageing; bladder; bladder hyperactivity; cholinergic; nerve-mediated contractility; nitrergic; urethra