Effects of endocrine state on sociosexual behavior of female rats tested in a complex environment.

The influence of both natural and artificially induced endocrine states on sociosexual behavior of the female rat was examined during 15-min behavioral observations in a complex testing apparatus that allowed the test females to control their contacts with sexually active and passive males and ovariectomized (OVX) females. Factor analysis of the behavioral measures for all test females indicated separate loadings on a lordotic behavior factor; a factor for the test females' preference for proximity to OVX females or passive males; and a factor for the test females' locomotion between portions of the testing apparatus. Behavioral variables loading on these factors were influenced by endocrine state, but the nature of the relation between behaviors and endocrine state varied between factors. The utility of the present testing situation in investigations of the neuroendocrine substrates underlying the motivational aspects of feminine reproductive behavior is examined.

Sociosexual behaviors of female rats during and after chronic treatment with the sympatholytic agent guanethidine.

Ovariectomized female rats were chronically administered saline or guanethidine sulfate, a drug that blocks adrenergic neurons and, when chronically administered, results in peripheral sympathectomy. The females were periodically injected with estradiol benzoate and progesterone and tested for sexual behaviors before, during and after the six-week period of daily guanethidine or saline injections. Tests for copulatory behavior included tests for lordotic responsiveness to manual stimulation and tests of sociosexual behaviors displayed by the females in a complex testing environment. The complex environment permitted the test females to control their coital contacts with sexually active males and their interactions with sexually inactive males and ovariectomized female rats. Guanethidine treatment did not alter lordotic responsiveness to manual stimulation but did reduce the frequency of copulatory acts engaged in by the females in the complex environment. During the first test in the complex environment following the start of drug injections, the guanethidine-treated females, in comparison to saline-treated females, displayed a lower frequency of lordotic behavior during coital contacts. The changes in behavior produced by the sympathetic drug, guanethidine, implicate the autonomic nervous system in the regulation of copulatory pacing in the female rat.

Effects of vagino-cervical stimulation upon sociosexual behaviors in female rats.

The role of vagino-cervical stimulation in the control of feminine copulatory behavior in the behaviorally estrous rat was examined in a complex environment that allowed the test female to pace her contacts with sexually active males, sexually passive males and ovariectomized females. Manipulations of vagino-cervical stimulation by administration of a topical anesthetic or by probing with a glass rod, immediately before testing in the complex environment, did not significantly alter any aspect of behavior in behaviorally estrous females. Transection of the pelvic nerve increased the number of intromissions and ejaculations that the females received and increased the amount of time that the females spent with the sexually active males. The present results implicate the pelvic nerve in the modulation of motivation for coital contacts in the female rat.

Lesions confined to the ventromedial hypothalamus decrease the frequency of coital contacts in female rats.

Ovariectomized female rats received either bilateral radiofrequency lesions of the ventromedial nucleus of the hypothalamus (VMH) or control treatments and were tested for copulatory activity following either estrogen (E) alone, or E plus progesterone (P) administration. In separate experiments the females were tested in two testing apparatuses both of which allowed the test females to control their contacts with sexually active males. One of the testing apparatuses also allowed the females to control their contacts with sexually inactive males and ovariectomized females. Females receiving VMH lesions engaged in fewer coital contacts with sexually active males than sham-operated females in the E plus P condition. Lesioned females also tended to spend less time with sexually active males than did sham operates in both the E and E plus P hormonal conditions. The VMH-lesioned females did not differ from the sham-operated females in the ability to display lordosis during the coital contacts or the frequency and duration of visits to the inactive males or ovariectomized females. The sham-operated females did have some transitory alterations in copulatory behavior in comparison to unoperated control females.

p-Chlorophenylalanine alters pacing of copulation in female rats.

When tested in apparatus that allowed them to determine their contacts with conspecifics, including sexually active male rats, estrogen- and progesterone-treated female rats systemically treated with para-chlorophenylalanine (PCPA), a tryptophan hydroxylase inhibitor, showed reduced frequency of coital contacts and reduced duration of interactions with sexually active males. PCPA administration did not alter contacts with noncopulating males or other females nor did treated females differ from controls in ability to display lordosis or posing, both stereotyped behaviors characteristic of female rats in behavioral estrus. It is suggested that the alteration of temporal pacing of copulation in the PCPA-treated females is a result of drug-induced changes in the processing of exteroceptive stimuli.

Rat strain differences in copulatory behavior after para-chlorophenylalanine and hormone treatment.

The potentiation of masculine copulatory behavior in castrated male rats following systemic para-chlorophenylalanine (PCPA) treatment was found to be dependent upon the strain of rat and the recency of castration. Wistar (W) and Sprague-Dawley (SD) males displayed a decline in behavioral responsiveness to PCPA treatment following castration, the W males retaining their behavioral responsiveness longer than SD males. Castrated W males were also behaviorally more responsive to androgen replacement than were SD males. Ovariectomized W and SD females receiving estrogen replacement displayed a strain difference in hormonal sensitivity. In tests for feminine copulatory behavior, ovariectomized W females were behaviorally more sensitive to estrogen treatment than SD females. Ovariectomized and estrogen-primed females of both strains displayed potentiated lordotic behavior following chronic PCPA treatment. Concomitant treatment with dexamethasone to reduce adrenal steroid output abolished the potentiation of lordotic behavior found with PCPA treatment.

Ejaculatory pattern in female rats without androgen treatment.

Adult female rats receiving long-term estrogen treatment displayed the species-typical motor pattern of ejaculation during copulation. This hormone treatment produced pituitary hypertrophy and concomitant pressure damage to brain areas dorsal to the pituitary, but did not cause clitoral hypertrophy. The demonstration of the ejaculatory pattern in perinatally untreated female rats indicates that the potential for the expression of the ejaculatory or "orgasmic" pattern is not dependent on exogenous androgen at any stage of development and is more widely represented among female mammals than previously believed.