Pituitary adenylate cyclase-activating polypeptide and its receptor PAC1 in the testis of Triturus carnifex and Podarcis sicula

The pituitary adenylate cyclase-activating polypeptide (PACAP) is a member of the glucagon-related family that occurs in two amidated forms with 38 (PACAP38) and 27 (PACAP27) amino acids. First discovered in the brain, it was then localized in several peripheral tissues of mammals, including the testis. However, current knowledge of the expression and function of PACAP and its receptor PAC1 in the reproductive system of non-mammalian vertebrates, and particularly in the testis, is still limited. The aim of this work was to study the presence of PACAP and its receptor PAC1 in the testis of two non-mammalian vertebrates during the breeding season: the crested newt Triturus carnifex and the wall lizard Podarcis sicula. The expression and distribution of this neuropeptide and its receptor PAC1 were investigated by using in situ hybridization and immunohistochemistry techniques. Our results demonstrated that PACAP and its receptor PAC1 were highly represented in the testis of these two species. In particular, we showed that they are present within some germ cells and that PACAP, unlike in mammals, is expressed also in the somatic cells (Sertoli and Leydig cells) of the testis of these two non-mammalian vertebrates, suggesting that this neuropeptide is involved in the hormonal control of spermatogenesis and steroidogenesis.