Hormonal Control of Male Reproductive Behavior in the Lizard, Anolis carolinensis: Role of Testosterone, Dihydrotestosterone, and Estradiol*

Abstract

The androgen aromatization hypothesis was examined in the male lizard, Anolis carolinensis. After castration, sc silastic implants of testosterone (T) restored both challenge and courtship behavior, while dihydrotestosterone (DHT) or 17beta-estradiol (E) had no effect on male behaviors. Both T and DHT, but not E, stimulated hypertrophy and colloid production by the renal sex segment, a secondary sexual characteristic of male lizards. In two separate studies, castrates received DHT in combination with E. In each replicate, half of the castrates responded with increases in courtship behavior after hormone treatment. Epithelial cell height of the sex segment of all DHT and E-treated castrates was comparable to T- or DHT-treated castrates, but colloid production was not stimulated. These experiments indicate that in this species, treatment with T stimulates both sexual behavior and secondary sex character development, whereas treatment with E alone is without effect centrally or peripherally.

Androgen Metabolism in the Brain of the Green Anole Lizard (Anolis carolinensis): Effects of Sex and Season

“…In male anoles, 5␣-reductase affects sexual behaviors by acting on T. This androgen predominates in the circulation of breeding male anoles (reviewed in Crews, 1980;Moore and Lindzey, 1992) and it is potent in activating courtship and copulatory behaviors in castrated males (Noble and Greenberg, 1941;Mason and Adkins, 1976;Crews et al, 1978;Adkins and Schlesinger, 1979;Winkler and Wade, 1998;Rosen and Wade, 2000). Moreover, inhibition of 5␣-reductase attenuates the stimulatory effects of T on courtship displays (Rosen and Wade, 2000).…”

“…These behaviors are followed by copulation if the female is receptive. Although T is consistently the most effective facilitator of sexual behavior in male anoles (Noble and Greenberg, 1941;Mason and Adkins, 1976;Crews et al, 1978;Adkins and Schlesinger, 1979;Winkler and Wade, 1998;Rosen and Wade, 2000), hormonal manipulation studies suggest that 5␣-reduction also plays an important role. For example, peripheral or central administration of the 5␣-reduced metabolite DHT reinstates sexual behavior in castrated male anoles (Adkins and Schlesinger, 1979;Crews and Morgentaler, 1979;Huang, 1979; but see Crews et al, 1978, andWade, 2000), and preventing its production (inhibiting 5␣-reductase activity) blocks the effects of T on behavior (Rosen and Wade, 2000).…”

“…Aromatase activity does not appear to play as critical a role. Systemic administration of E2 alone is ineffective in facilitating male sexual behaviors (Mason and Adkins, 1976;Crews et al, 1978;Winkler and Wade, 1998), and inhibition of the aromatase enzyme by Fadrozole does not prevent the behavioral effects of T in male anoles (Winkler and Wade, 1998). However, E2 can restore male anole courtship behavior if directly implanted into the anterior hypothalamus/preoptic area or administered peripherally with DHT .…”

Courtship and copulation in the adult male green anole: Effects of season, hormone and female contact on reproductive behavior and morphology

“…In unmanipulated animals, dewlap extensions occur far more often in the breeding (BS) than non-breeding (NBS) season, and copulation only occurs during the BS [34,46]. A seasonal increase in T, rather than its metabolites, is the primary regulator of male sexual behavior [28,53,54,74,94].…”

Effects of season, testosterone and female exposure on c-fos expression in the preoptic area and amygdala of male green anoles

“…Courtship and copulatory behaviors in green anoles are facilitated by environmental conditions typical of the BS and are greatly diminished during the NBS. T, rather than its metabolites, is the primary activator of these behaviors in males (Adkins and Schlesinger, 1979;Crews et al, 1978;Greenberg and Nobel, 1944;Jenssen et al, 2000;Lovern et al, 2004;Neal and Wade, 2007;O'Bryant and Wade, 1999;Rosen and Wade, 2000;Wade, 2005;Winkler and Wade, 1998). T and seasonal environmental conditions also affect forebrain morphology in the anole.…”