The effect of ovarian steroids on the response of the hen uterus to neurohypophysial hormones.

The purpose of the present study was to examine the effect of arginine vasotocin (AVT) and mesotocin (MT) on the uterine contractility in the immature chicken treated with gonadal hormones. It was found that AVT and MT produced dose-dependent contraction of the chick uterine strips. In the control group the mean threshold doses were: AVT - 4.5 ng/ml, MT - 130 ng/ml. Pretreatment with progesterone (P) or testosterone (T) resulted in a considerable reduction of the contractile response to AVT. Oestradiol (E) and combinations: E + T and E + P + T increased the sensitivity of the uterus to AVT. Testosterone treatment supressed and combinations E + T and E + P + T enhanced the uterine response to MT. The obtained results could be summarized as follows: 1) AVT and MT cause uterine contraction in vitro in the immature hen: 2) AVT is much more potent than MT: 3) ovarian steroids change the sensitivity of the hen uterus to AVT and MT.