Effects of progestins on sexual behaviour in castrated lizards (Cnemidophorus inornatus)

Abstract

In many male vertebrates, androgens stimulate, while progesterone inhibits, sexual behaviour. Testicular androgens also control sexual behaviour in males of the lizard Cnemidophorus inornatus. However, administration of progesterone will reinstate sexual behaviour in castrated animals. Increased doses of progesterone did not result in increased numbers of responders; at all doses tested approximately 36% (n = 45) of animals treated with progesterone responded as reliable courters. A high percentage (60-68%) of progesterone-sensitive individuals maintained their sensitivity over a period of months. A synthetic progestin 17,21-dimethyl-19-nor-4,9-pregnadiene-3,20-dione with low rates of metabolism and conversion, also stimulated sexual behaviour in castrated C. inornatus. Finally, the synthetic antiprogestin 11 beta-4-dimethylaminophenyl-17 beta-hydroxy-17 alpha-1-propinyl- 4,9-oestradiene-3-one inhibited the stimulatory effects of progesterone on sexual behaviour but failed to inhibit the stimulatory effects of androgens. These findings indicate an unusual departure from the characteristic pattern of steroid sensitivities of neural centres controlling sexual behaviour.

The reproductive cycle of the male house gecko, Hemidactylus flaviviridis, in relation to plasma steroid concentrations, progesterone receptors, and steroidogenic ultrastructural features, in Oman

“…These studies demonstrated the roles of E 2 and P in the regulation of the reproductive cycle (Edwards and Jones, 2001;Lindzey and Crews, 1988;Lindzey and Crews, 1992;Witt et al, 1994;Young et al, 1991).…”

“…Exogenous P has been shown to stimulate sexual behaviors in the male lizard Cnemidophorus inornatus (Lindzey and Crews, 1986). Restoration of sexual behavior in P-sensitive male whiptail lizards (C. inornatus) by synthetic progestin agonists indicated that P was producing this behavioral effect (Lindzey and Crews, 1988), and further, binding studies suggested that progesterone receptors (PR) mediated this response (Lindzey and Crews, 1993).…”

Biology of stress: interactions with reproduction, immunology and intermediary metabolism

“…The functional role of progesterone in male reptiles is still poorly defined. Interestingly, it stimulates the expression of sexual behaviour in male Cnemidophorus inornatus (Lindzey and Crews, 1988) whereas it is inhibitory in male Anolis earolinensis (Young et al, 1991).…”

Molecular characterization and brain distribution of the progesterone receptor in whiptail lizards

“…Work in both reptiles and rats reveal that exogenous progesterone at physiological levels stimulate copulatory behavior in castrated males [11,34–36,71,72,77]. Testosterone and progesterone can also synergize in promoting male-typical sexual behavior [34,35,71,72,77], in a similar manner to estradiol and progesterone in stimulating female-like sexual behavior in rats [53]. Although progesterone is important in modulating social behavior across vertebrates, relatively little is known about the functional biochemistry and distribution of the progesterone receptor in non-mammalian vertebrates.…”