Immunohistochemical studies on the distribution of nerve fibers in the human prostate with special reference to the anterior fibromuscular stroma

Abstract BACKGROUND Although the anterior fibromuscular stroma (AFMS) comprises up to one third of the total bulk of the prostate, its physiological function remains unknown. We recently reported the possible contribution of the AFMS to micturition. The aim of this study is to reveal the differences in the distribution of innervation between the AFMS and the other regions of the prostate. METHODS We performed immunohistochemical stainings using antibodies such as protein gene product (PGP) 9.5, tyrosine hydroxylase(TH), neuropeptide Y (NPY), and vasoactive intestinal peptide (VIP). Morphometric analysis was made to examine the density of peripheral nerve fibers containing PGP 9.5, TH, NPY, and VIP by using a computer‐assisted imaging system. RESULTS The number of PGP 9.5‐immunoreactive (IR) nerve fibers and the smooth muscle in the AFMS decreased from the base to the apex of the prostate. TH‐IR nerve fibers were more abundant in the AFMS than in the transition zone. NPY‐ and VIP‐IR nerve fibers were less numerous in the AFMS than in the peripheral zone. CONCLUSIONS This study is the first to demonstrate that the AFMS has peculiar neuronal innervation. We observed significantly different innervation in the AFMS compared with the other regions of the prostate. Prostate 48:242–247, 2001. © 2001 Wiley‐Liss, Inc.