Male Rats With Inherited Insensitivity to Androgen Show Reduced Sexual Behavior

Abstract

Pseudohermaphroditic Stanley-Gumbreck male rats showed infrequent and incomplete copulatory responses to receptive females. Administration of testosterone propionate produced no increase in this behavior. Injections of estradiol and progesterone induced the pseudohermaphrodites to exhibit lordosis when mounted by stimulus males, but feminine responses were no more frequent than those of normal males given the same hormonal treatment. The hypothesis is suggested that early in development sufficient endogenous testis hormone is produced to cause normal desensitization of feminine behavioral mechanisms to estradiol, but that mechanisms for male behavior are not normally sensitized to testosterone.

The role of androgen receptors in the masculinization of brain and behavior: What we've learned from the testicular feminization mutation

“…Olsen, 1979 Masculine mating behavior Rat Tfm ♂'s show reduced masculine sexual behavior compared to wt ♂'s. Beach and Buehler, 1977;Olsen and Whalen, 1981;Olsen, 1992;Shapiro et al 1976 Mouse Tfm ♂'s show reduced masculine sexual behavior compared to wt ♂'s, a difference that is eliminated in E2 treated mice. Ono et al, 1974;Bodo and Rissman, 2007 Partner Preference Rat Tfm ♂'s show a masculinized partner preference.…”

“…The role of ARs in the development of masculine sexual behavior (i.e., mounting behavior), however, is not as clear. Tfm male rats have been reported to show variable, but consistently reduced sexual behavior compared to wt males (Beach and Buehler, 1977;Hamson et al, 2005;Olsen and Whalen, 1981;Olsen, 1992;Shapiro et al, 1976). Interestingly, c-Fos expression following a sexual encounter was similar in relevant brain areas (such as the medial preoptic area (MPOA) and medial amygdala (MeA)) of wt and Tfm males that showed comparable levels of sexual behavior (Hamson et al, 2005), suggesting that activation of relevant neural circuitry may be normal in Tfm rats despite the lack of functional ARs.…”

“…As reviewed above, several brain areas believed to regulate sexual behavior in rodents (MePD, VMH, SDN-POA, BST) are demasculinized in Tfm male rats, and thus may contribute to their reduced sexual behavior (Beach and Buehler, 1977;Shapiro et al, 1976;Hamson et al, 2005). In this instance, it is easier to infer how demasculinization of sex behavior-related circuitry could lead to a demasculinization of behavior.…”

“…However, morphological differences are not the same in the two Tfm models and it is difficult to interpret how an increased GCL volume in Tfm male rats, or a lack of GCL laterality in Tfm male mice, could result in spatial memory impairment. It is possible that morphological differences in unexamined hippocampal regions, such as CA1 of Tfm males, contribute to this deficit.As reviewed above, several brain areas believed to regulate sexual behavior in rodents (MePD, VMH, SDN-POA, BST) are demasculinized in Tfm male rats, and thus may contribute to their reduced sexual behavior (Beach and Buehler, 1977;Shapiro et al, 1976;Hamson et al, 2005). In this instance, it is easier to infer how demasculinization of sex behavior-related circuitry could lead to a demasculinization of behavior.…”

Androgen receptors are required for full masculinization of the ventromedial hypothalamus (VMH) in rats

“…TFM males do not display lordosis despite their feminine appearance (Olsen, 1979), so they are defeminized, presumably by aromatized metabolites of testosterone acting on estrogen receptors. They also show infrequent and incomplete male copulatory responses to receptive females (Beach and Buehler, 1977), but that could be due to either incomplete masculinization of brain sites such as the VMH or to the absence of normal male genitalia.…”