Has active immunization against gonadotrophin-releasing hormone any effect on testis innervation in the pig? An immunohistochemical study.

The innervation of porcine testes was studied in intact animals and in boars undergoing active immunization against gonadotrophin-releasing hormone (GnRH) by means of immunohistochemistry using antibodies to tyrosine hydroxylase (TH), dopamine beta-hydroxylase (D beta H), vasoactive intestinal polypolypeptide (VIP), neuropeptide Y (NPY), synaptosome-associated protein of 25 kDa (SNAP-25) and protein gene product 9.5 (PGP 9.5). Moreover, the distribution of luteinizing hormone (LH) receptors in clusters of Leydig cells was also investigated. To identify these cells easily, either the NADPH-diaphorase histochemical technique or the Mayer counter-staining procedure was applied. Differences in the distribution pattern and relative density of particular subsets of intratesticular nerve fibres were observed in immunized boars as compared to those found in the intact animals. In the testes of non-treated animals, only single TH-immunoreactive (TH-IR) nerve fibres were observed. However, many D beta H-IR nerve terminals surrounded blood vessels in the tunica albuginea and parenchyma. Very scarce VIP-IR nerves occurred only in the tunica albuginea, mainly in close vicinity to blood vessels. Immunoreactivity to NPY occurred in single nerve fibres. Immunoreactivity to SNAP-25 and PGP 9.5 was found in single nerve fibres distributed mainly in the tunica albuginea. The interstitial cells were heavily stained for LH-receptors and NADPH-diaphorase. In the testes of immunized animals, only single TH-IR nerve fibres, scattered mainly in the tunica albuginea, were observed. Some TH-IR nerve terminals were also encountered in the parenchyma of the organ, where they were always associated with blood vessels. D beta H-IR nerve fibres formed a dense network distributed throughout the testis in association with the capsule, vasculature and interstitium. Some fibres were observed to run between seminiferous tubules. VIP-IR nerve fibres were located in the neighbourhood of blood vessels in the tunica albuginea and parenchyma. Only single VIP-IR nerves were found between seminiferous tubules. Numerous NPY-IR nerve fibres occurred in the tunica albuginea and parenchyma of the organ. SNAP-25-IR and PGP 9.5-IR nerve terminals formed a dense network distributed throughout the testis and many fibres were observed between seminiferous tubules. Interstitial cells were very weakly stained for LH receptors or NADPH-diaphorase.