The grey squirrel, an invasive species, threatens the Eurasian red squirrel’s conservation, particularly in Umbria, Italy. Understanding its reproductive biology is essential to limiting its reproductive success. This study investigates the NGF system and its receptors (NTRK1 and p75NTR) in the testes of male grey squirrels, following prior research on female reproductive biology. NGF plays a role in testicular morphogenesis and spermiogenesis in animals and humans. As part of the LIFE Project U-SAVEREDS, eighteen squirrels were captured and classified into three morphotypes (immature, pubertal, and active spermatogenesis). NGF and its receptors were analyzed using real-time PCR, western blotting, immunohistochemistry, and plasma levels measured via ELISA. NGF qPCR expression levels were significantly higher during puberty compared to the immature and spermatogenesis stages (p p value < 0.01. The co-localization of NGF and its receptors suggests that NGF, produced by Leydig cells, regulates testis development and reproductive success through autocrine or paracrine mechanisms, potentially involving an unidentified pathway.
