The VIP/VPACR system in the reproductive cycle of male lizard Podarcis sicula

Our results demonstrate that, differently from mammals, where VIP is present only in nerve fibres innerving the testis, an endotesticular synthesis takes place in the lizard and the VIP synthesis changes throughout the reproductive cycle. Moreover, the VIP/VPAC receptor system distribution observed in germ and somatic cells in various phases of the cycle, and particularly in the autumnal resumption and the reproductive period, strongly suggests its involvement in both spermatogenesis and steroidogenesis. Finally, the wider distribution of VIP in lizards with respect to mammals leads us to hypothesize that during the evolution the synthesis sites have been transferred from the testis to other districts, such as the brain.