Expression of arginine vasotocin and estrogen receptor alpha (ERα) in the shell gland altered by the specific phase relations of neural oscillations affects the reproductive physiology of Japanese quail.

In order to study the effect of specific phase relation of neural oscillations on reproductive regulation and the response of AVT (the avian homologue of mammalian AVP) the expression of AVT in the shell gland was monitored in sexually immature quail. In this study 3-week-old female Japanese quail were administered with serotonin precursor, 5-hydroxytryptophan followed by the dopamine precursor, l-dihydroxyphenylalanine at interval of 8h and 12h daily over a period of 13days. At thirty two days post treatment, a significant decrease in gonadal activity was seen in 8h quail although 12h quail exhibited an increase as compared to controls. A significant decrease in plasma estradiol level was noted in 8h quail while 12h exhibited no significant difference compared to controls. To address the relative roles of estrogen mediated action we also investigated estrogen receptor alpha (ER-α) expression and localization in the shell gland by visualizing it through confocal immuno-fluorescence microscopy. Results indicate increased expression of immunoreactive (ir)-AVT (myometrium), ir-ER-α (epithelial cells of endometrial region), along with significant increase in hypothalamic, plasma and shell gland AVT and a rapid increase in egg laying thus maintaining full breeding condition in 12h while low expression of ir-AVT and ir-ER-α was observed in 8h quail along with a significant decrease in hypothalamic, plasma and shell gland AVT with the suppression of gonads thereby stopping the egg-laying behaviour was noted. These findings not only suggest the modulation of gonadal development by changing the specific phase relation of neural oscillations but also demonstrate a parallel relation of AVT and gonadal activity in both conditions. It is concluded that the egg laying performance in response to AVT is regulated by the temporal phase relationship of neurotransmitters, and in part, this effect appears to be estrogen dependent.