Inhibition by Corpora Atretica of Ovarian Sensitivity to Environmental and Hormonal Stimulation in the Lizard, Anolis carolinensis 1 DAVID CREWS AND PAUL LICHT Department of Zoology, University of California, Berkeley, California 94720 ABSTRACT. Female Anolis carolinensis are sexu- ally refractory to both environmental and hormonal stimulation immediately following the breeding season. This refractory period coincides with the appearance of corpora atretica (CA). Two' ap- proaches were used to determine whether the presence of the CA might be responsible for this decreased sensitivity. Exposure of refractory females to a stimulatory environmental regime dem- onstrated that vitellogenesis is inversely related to the occurrence of CA. Secondly, treatment of refrac- tory females with ovine FSH (either 10 or 50 fig on alternate days for 16 days), demonstrated that re- moval of the CA increased ovarian and oviducal responsiveness to exogenous gonadotropin by at least 5-fold. These data indicate that the CA main- tain sexual refractoriness by suppressing ovarian sensitivity to both environmental and hormonal stimulation. (Endocrinology 95: 102, 1974) T HE annual ovarian cycle of the lizard Anolis carolinensis may be divided into three distinct periods: previtel- logenesis, vitellogenesis and regression. Previtellogenesis, lasting from November to February, is characterized by inactive ovaries containing only small translucent, unyolked, follicles and atrophic oviducts. During this phase, the follicles are initially relatively uniform, ranging from 1.2-1.8 mm in diameter, but gradually increase to 1.8-2 mm by late February. Yolk deposi- tion (vitellogenesis) begins in March; at this time a single follicle begins to accumu- late yolk and enlarges rapidly until it is ovulated at about 8 mm by the end of 2 weeks. During the ensuing breeding sea- son, a single ovarian follicle matures and is ovulated alternately between ovaries every 10-14 days (1-9). Vitellogenesis ceases in late August and the yolking follicles al- ready present in the ovary begin to degen- erate rapidly. Follicles undergoing atresia differ from normal follicles and from cor- Received December 6, 1973. 1 Experiment 1 was conducted while DC was a NIMH predoctoral fellow at the Institute of Animal Behavior, Rutgers University (Grant No. GM-1135, Daniel S. Lehrman, Program Director). Experiment 2 was supported by NSF Grant No. GB 35241X to PL. pora lutea in that they are highly vas- cularized, discolored (orange-yellow), flaccid, and mottled in appearance. These corpora atretica (CA) are gradually ab- sorbed, and disappear completely from the ovary during October. Experimental studies indicate that female A. carolinensis are sexually refractory dur- ing the early portion of the regressive phase of the annual cycle. For example, environmental (social and climatic) stimuli that promote rapid ovarian growth in winter and spring are generally ineffective in stimulating females in September and October (6,11). Furthermore, the females appear to respond less rapidly to exogenous gonadotropic hormones during the fall than in winter and spring (12); thus, refractori- ness may be due partly to changes in ovarian hormonal sensitivity. The close temporal relationship that is evident between the presence of the atretic follicles and the period of reduced sexual responsiveness suggested that the CA might play an important role in maintaining the refractory condition. To test the possi- bility that the CA might have some inhibi- tory effect on ovarian sensitivity to both environmental and hormonal stimulation, we first examined the correlation between the disappearance of the CA and the termi- 102 The Endocrine Society. Downloaded from press.endocrine.org by [David Crews] on 01 December 2014. at 13:20 For personal use only. No other uses without permission. . All rights reserved.