title: Relaxing effect of acetylcholine on phenylephrine-induced contraction of isolated rabbit prostate strips is mediated by neuronal nitric oxide synthase.
abstract: OBJECTIVE
  The location of acetylcholinesterase-containing nerve fibers suggests a role for acetylcholine in both contractility and secretion in the prostate gland. The colocalization of nitrergic nerves with cholinergic nerves, and the cotransmission of nitric oxide with acetylcholine in cholinergic nerves, has been demonstrated in the prostate glands of various species. Thus, we investigated the effects of acetylcholine on phenylephrine-induced contraction and the correlation between cholinergic transmission and nitric oxide synthase by using isolated prostate strips of rabbits.
  
  
  METHODS
  Isolated prostate strips were contracted with phenylephrine and then treated with cumulative concentrations of acetylcholine. Changes in acetylcholine-induced relaxation after preincubation with NG-nitroarginine methyl ester, 7-nitroindazole, and aminoguanidine were measured. The effects of selective muscarinic receptor antagonists were also evaluated.
  
  
  RESULTS
  In the longitudinal phenylephrine-contracted strip, the cumulative application of acetylcholine (10(-9) to 10(-4) M) elicited a concentration-dependent relaxation effect. Acetylcholine-induced relaxation was inhibited not only by nitric oxide synthase inhibitors (10 µM L-NAME or 10 µM 7-nitroindazole) but also by 10 µM atropine and some selective muscarinic receptor antagonists (10(-6) M 11-([2-[(diethylamino)methyl]-1-piperdinyl]acetyl)-5,11-dihydro-6H-pyrido[2,3-b][1,4]benzodiazepine-6-one and 10(-6) M 4-diphenylacetoxy-N-methyl-piperidine). In contrast, relaxation was significantly increased by pretreatment of the strips with 10 mM L-arginine.
  
  
  CONCLUSIONS
  Acetylcholine relaxed phenylephrine-induced contractions of isolated rabbit prostate strips. This relaxation may be mediated via both cholinergic and constitutive nitric oxide synthase with both the M2 and M3 receptors possibly playing key roles.
authors.affiliation: Department of Urology, Viet Duc University Hospital, Hanoi, Vietnam.
authors.forename: Hoai Bac
authors.initials: HB
authors.lastname: Nguyen
authors.forename: Shin Young
authors.initials: SY
authors.lastname: Lee
authors.forename: Soo Hyun
authors.initials: SH
authors.lastname: Park
authors.forename: Moo Yeol
authors.initials: MY
authors.lastname: Lee
authors.forename: In Ho
authors.initials: IH
authors.lastname: Chang
authors.forename: Soon Chul
authors.initials: SC
authors.lastname: Myung
keywords: Acetylcholine; Muscarinic M2 receptor; Muscarinic M3 receptor; Nitric oxide synthase type I; Prostate