Neuropeptides in the urinary tract of male sheep lambs

Small ruminants are often presumed to be at a higher risk of developing obstructive urolithiasis after early castration. However, the underlying pathophysiology and histological correlation of this assumption is unknown. This study examines the neuropeptide distribution of the lower urinary tract in male lambs in respect to castration status or a recent history of obstructive urolithiasis. Various tissue samples were taken and examined. The sample consisted of 34 male lambs, aged six months (n = 11 early and n = 11 late castration; n = 12 intact), and 8 rams that had undergone necropsy due to fatal outcome after obstructive urolithiasis. Immunohistochemical stainings for substance P (SP), vasoactive intestinal polypeptide (VIP) and neurofilaments (NF) were performed and compared between the groups. A significant reduction in immunoreactive signals of SP, VIP and NF was evident in the urolithiasis group (SP and NF: P < 0.0001; VIP: P = 0.02). The results of immunohistochemistry suggest that castration had no effect on the content of neuropeptides, as well as the innervation density of the urethra in the male lambs. In the case of. obstructive urolithiasis, the pattern of neuropeptide distribution was severely disturbed and cell damage lead to a reduction in detectable periurethral bundles of nerve fibers. The severe tissue damage was assumed to have a negative impact on the outcome of treatment, leading to complications such as urethral strictures. These, in turn, often result in relapses.