Endocrine Abstracts

Vasotocin (AVT), the avian homolog of vasopressin, is synthesized in the BSTM of chickens in addition to the hypothalamo hypophysial axis. In previous reports, sex specific AVT–immunoreactivity(ir) in male BSTM (Jurkevich et al. 1999) and it’s ontogeny were demonstrated (Grossmann et al. 2002). In addition, galanin (Gal) was found in male BSTM co-localized to AVT. In the present study, the ontogeny of AVT- and Gal-ir was investigated in the SON as part of the magnocellular AVT system and the limbic BSTM. Chickens at the age of days D2, D14, D35, D70, and D112 and adults were processed for double immunohistochemistry and confocal microscopy. In SON, only AVT was detected in chicks of D2 to D70 in either sex. At D112, galanin was found in both sexes with up to 75% co-localization to AVT. In adult chickens, Gal was not visible in male and female SON. In BSTM, Gal as well as AVT were expressed in both sexes at D2. Significantly reduced cell numbers and ir-intensities of both peptides were recorded at D14. At D35, neither of the peptides were detected. Gal and AVT ir neurons were clearly detected again in BSTM of D70 males only. At D112, the pattern of AVT and Gal ir were not different compared to adult males. In contrast to mammals, female chickens synthesize no Gal in BSTM after D35.

This study demonstrates for the first time close relationship between AVT and Gal peptidergic systems in BSTM and provides first evidence for a sex, age ad region dependent Gal–expression in chickens.