DEVELOPMENTAL-CHANGES IN GALANIN RECEPTORS IN THE QUAIL OVIDUCT AND THE EFFECT OF OVARIAN SEX STEROIDS ON GALANIN RECEPTOR INDUCTION

We have recently isolated an oviposition-inducing peptide from mature quail oviducts identified as avian galanin. This peptide evoked vigoro us contractions of the uterine oviduct through binding to receptors lo cated in the uterus. The questions arising from these findings are: wh at changes occur in galanin receptors in the uterus during maturation, and what is the hormonal factor(s) that induces uterine galanin recep tors? Therefore, the present study examined changes in uterine galanin receptors with age and the effect of administration of ovarian sex st eroids on galanin receptors in the quail. Immature females reared unde r long day (LD) photoperiods from 4 weeks of age demonstrated a progre ssive increase in specific galanin binding per both unit uterine weigh t and per whole uterus concurrent with uterine development during 4-13 weeks. Scatchard plot analyses of the binding to the uterine preparat ion showed that the equilibrium dissociation constant (K-d) was about 0.30-0.34 nM regardless of age, and the change in galanin binding duri ng uterine development was due to a change in the number of binding si tes. Plasma 17 beta-estradiol and progesterone concentrations were alm ost constant between 4-6 weeks and tended to increase thereafter. Admi nistration of 17 beta-estradiol to immature females for 1 week increas ed not only uterine weight but also specific galanin binding per unit uterine weight, whereas progesterone increased only the binding per un it uterine weight. Both sex steroids also induced an increase in total binding per uterus. Combined administration of 17 beta-estradiol and progesterone induced marked increases in the galanin binding, and the effect was not additive but, rather, was synergistic. Scatchard plot a nalysis showed that the number of binding sites, but not the K-d, was increased by steroid treatment. Administration of 17 beta-estradiol or progesterone increased each circulating steroid level to that relativ ely similar to the maximal levels observed in females exposed to LD.Th us, ovarian sex steroids may contribute at least in part as hormonal f actors to galanin receptor induction, which takes place in the uterine oviduct during development.