Arginine vasotocin‐induced in vitro oviductal contractions in Anolis carolinensis: Effect of steroid hormone pretreatment in vivo

Ovariectomized female Anolis carolinensis were treated for 14 days with one of the following regimens: (1) estradiol (1 μg/0.05 ml saline/day), (2) progesterone (10 μg/0.05 ml saline/day), or saline (0.05 ml/day). Oviducts then were removed surgically and placed in a bath containing Munsick's solution, to which was added either arginine vasotocin (30 ng/ml) or saline. Although saline produced no effects, AVT‐treated oviducts exhibited rhythmic contractions regardless of pretreatment regimen. Five parameters of the contractions measured were: (1) duration, (2) amplitude, (3) Strength (duration × amplitude), (4) frequency, and (5) rest. Each parameter then was analyzed using a 2 × 3 × 8 mixed, repeated measure design and analysis. Pretreatment with estradiol and progesterone significantly affected contraction strength, amplitude, and duration. Progesterone pretreatment produced oviductal contractions significantly stronger than saline pretreatment (p < 0. 001), whereas estradiol pretreatment produced significantly weaker contractions that saline pretreatment (p < 0.001). These findings are in contrast to those previously recorded for mammals and other reptiles in which estrogens support and progesterone inhibits uterine contractions. These data may suggest a unique adaptation of hormonal control of oviductal contraction in A. carolinensis to the alteration of oviposition during this lizard's reproductive cycle.