Galanin in the lizard oviduct: Its distribution and relationships with estrogen, VIP and oviposition

The distribution of neurons containing galanin immunoreactivity (Gal/IR) ha s been detected in the oviduct of the lizard Podarcis s. sicula during the main phases of its sexual cycle and after 17 beta-estradiol treatment. Indi rect immunofluorescence technique was applied both to cryostatic sections a nd whole mount preparations, and Western blot analysis, with an antibody di rected against mammalian galanin (Gal), was performed with lizard oviduct e xtracts. Colocalization of Gal with vasoactive intestinal polypeptide (VIP) was also studied as well as Gal effects on egg deposition. In the quiescen t oviduct of nonreproductive females, scanty Gal/IR fibres were found in th e uterine-vaginal segment. During the reproductive period a gradual increas e of positive nerve fibres and cell bodies were found distally in the lizar d oviduct and the vagina revealed a reactive nerve population denser than e lsewhere. Gal-IR nerve structures were present either in the musculature or mucosa and in the intermuscular layer they were organized in a nerve netwo rk. In the oviduct of non-reproductive females, 17 beta-estradiol administr ation induced a significant increase of neurons containing Gal/IR. This hor mone could be involved in the egg laying by means of galanin action and thi s hypothesis is supported by the induction of premature oviposition in pre- ovulatory females after Gal administration. Western blot analysis validates this peptide as true Gal, recognising one protein band with a molecular we ight (3.2 kDa), similar to that of porcine Gal. Double labelling studies sh owed the copresence of Gal and VIP in some neurons.