Endogenous nitric oxide-mediated relaxation and nitrinergic innervation inthe rabbit prostate: The changes with aging

BACKGROUND. Nitric oxide (NO) plays the key role in the non-adrenergic non- cholinergic (NANC) nerve-mediated relaxation of prostate. We tried to deter mine whether nitrinergic innervation of the prostate is reduced with aging, and whether a reduction of this innervation alters the relaxant properties of prostatic tissue. METHODS. The prostate isolated from young rabbits at the age of 3 months an d aged rabbits at the age of 24 months was used. Pharmacologic experiments using electrical field stimulation (EFS) were performed on strips of prosta te. Nitrinergic nerves were identified histochemically by the presence of N ADPH diaphorase reactivity. RESULTS. The prostate weighed 0.34 +/- 0.06 g in the young and 0.78 +/- 0.1 3 g in the aged (P < 0.01). Electrical stimulation caused frequency-depende nt relaxation that was inhibited by N-nitro-L-arginine and increased by L-a rginine. Maximum relaxant rates of noradrenaline-induced tone were 41.3<plu s/minus>1.8% and 22.7 +/-0.6% in the young and the aged (P < 0.01), respect ively. Exogenous NO caused concentration-dependent relaxation of the prosta te. Both relaxation induced by electrical stimulation and exogenous NO were inhibited by LY83583 (a guanylate cyclase inhibitor). Ln all specimens, NA DPH diaphorase activity was observed in the smooth muscle layer of the pros tatic stroma and capsule. However, NADPH diaphorase positive nerves were si gnificantly less in the aged than in the young (P < 0.01). CONCLUSIONS. As a result of these findings, it is suggested that both NO-me diated relaxation and nitrinergic innervation are reduced with aging in thi s animal model. Prostate 48.40-46, 2001. (C) 2001 WiIey-Liss, Inc.