Lordosis Behaviour in Male, Female and Androgenized Female Rats

Abstract

Sex differences in the lordodis response of adult rats to ovarian hormones were studied in a series of experiments. Male rats were less sensitive to oestradiol benzoate (OB, a single injection of 10, 100 or 1000 mug/kg or seven daily injections of 2, 10, or 50mglkg)then were female rats. Oestradiol benzoate-primed (10 mglkg)female, but not male, rats showed dose-dependent responses to progesterone (0-4, 2-0 or 10-0 mg/kg/. male rats responded clearly to progesterone (2 mg/rat) only when primed with a high dose of OB (100 mug/rat). Display of the whole pattern of female sexual behaviour was induced in male rats by treatment with 100 mug OB and 2 mg progesterone. Female rats treated with 1 mg testosterone propionate (TP) on day 4 of life, ovariectomized as adults and tested under the same endocrine conditions as the rats described above, retained behavioural OB sensitivity but responded poorly to progesterone. Evidence is presented that ovarian secretions during development significantly modify the response of neonatally TP-treated and normal female rats to OB in adulthood.

Behavioral defeminization by prenatal androgen treatment in rats can be overcome by sexual experience in adulthood

“…The present studies demonstrate that the repeated administration of EB (alone or in combination with P) at four-day intervals (as occurs during the rat's natural ovarian cycle) is capable of overcoming the initial deficit on lordosis measures as well as some appetitive measures observed in PNAFs. The recovery of hops/darts seen in our study parallels the report by Södersten (1976) on ear wiggling in PNAFs and males treated with pulsed estradiol followed by P, yet is in contrast to the lack of hops/darts seen in males reported by Olster and Blaustein (1988). One important difference is the magnitude of the androgenization.…”

“…Following gonadectomy in adulthood, perinatally androgenized female rats, as well as male rats (that are presumably fully androgenized), treated with estradiol followed by P display rates of lordosis similar to that observed in OVX control rats in adulthood, provided estradiol is administered in a pulsed fashion (Olster and Blaustein, 1988;Södersten, 1976;Södersten et al, 1983). In some cases, male rats are also capable of displaying P-facilitated appetitive sexual behaviors such as earwiggling (Södersten, 1976), although not more active forms such as hops and darts (Olster and Blaustein, 1988). Whether permanent deficits occur on other measures of appetitive sexual behaviors, such as full solicitations (McClintock, 1984), is not known.…”

“…Following gonadectomy in adulthood, PNAFs as well as males display normal levels of lordosis when primed with estradiol and P, if estradiol is administered in a pulsed manner (Olster and Blaustein, 1988;Södersten, 1976;Södersten et al, Fig. 4.…”

Activation of Feminine Sexual Behavior in Castrated Male Rats by Intrahypothalamic Implants of Estradiol Benzoate

“…In females, 30 gauge implants alone elicit a high degree of lordosis responsiveness. Although in some strains of rats male are more likely to perform lordosis responses than in others, it is gen erally the case that more estrogen is required to stimulate such responsiveness than with females of the same strain [Davidson, 1969;Sodersten, 1976], Moreover, the well-known synergistic action of progesterone with estro gen in the production of behavioral estrus is not usually observed in males [Davidson, 1969], If, however, a sufficiently high dose of estro gen is used for priming, then males of at least one strain exhibit lordosis and ear-wiggling in response to systemically administered proges terone [Sodersten, 1976]. Males, then, are ap parently capable of a more complete range of receptive behaviors if the appropriate hor monal conditions are chosen.…”

The female phenotype: Nature's default?

“…In studies of rodents, prepubertal ovariectomy (OVX) has been found to significantly alter a variety cf sexually dimorphic behaviors in a male-typical direction, including decreased receptive sexual behavior (lordosis; Blizard & Denef, 1973;Sodersten, 1976), decreased proceptive sexual behavior (darting, hopping, ear wiggling; Gerall et al, 1973), decreased open field behavior (Blizard & Denef, 1973;Denti & Negroni, 1975;Stewart & Cygan, 1980), decreased activity in aplus maze (Leret, Molina-Holgado, & Gonzalez, 1994;Zimmerberg & Farley, 1993), depressed active avoidance performance (Denti & Negroni, 1975), and decreased behavioral response to amphetamine (AMPH; Forgie & Stewart, 1994). At the anatomical level, neonatal treatment with an estrogen antagonist or estrogen mRNA antisense has been shown to reduce the volume of the sexually dimorphic nucleus of the preoptic area (SDN-POA) in female rats (Dohler, Hancke, et al, 1984;McCarthy, Schlenker, & Pfaff, 1993).…”