Mesencephalic participation in the control of sexual behavior in the female rat

Electric stimuli applied to both pudendal nerves evoked field potentials, unit responses, and multiunit responses in the ventrolateral midbrain, in and around the peripeduncular nucleus. Bilateral lesions placed in this region suppressed sexual behavioral responses (lordosis and courting behavior) of ovariectomized rats primed with 5, 10, 100, and 1,000 microgram of estradiol benzoate and 2 mg of progesterone per kilogram of body weight. It is proposed that the region in question represents a relay station for the integration of sensory and endocrine information concerned in the control of receptive sexual behavior in the female rat.     

Monoaminergic mediation of female sexual behavior.

Lordotic behavior was facilitated in estrogen-primed female rats by direct application of progesterone or serotonergic or beta-adrenergic receptor blockers to specific telencephalic, anterior hypothalamic-medial preoptic, or posterior hypothalamic sites. Blockade of the alpha-adrenergic system was ineffective in facilitating lordosis, as was the application of the active drugs to control sites in the thalamus or basal ganglia. Female soliciting behavior was not evoked by any of the treatments. It is concluded that the lordotic behavior component of the female rat's estrous behavior pattern is inhibited by a specific central monoaminergic system that also responds to progesterone. Soliciting behavior appears to be mediated by systems that are anatomically, and possibly neurochemically, separable from those regulating lordosis.     

Hippocampal and cerebellar single-unit activity during delay and trace eyeblink conditioning in the rat

In delay eyeblink conditioning, the CS overlaps with the US and only a brainstem-cerebellar circuit is necessary for learning. In trace eyeblink conditioning, the CS ends before the US is delivered and several forebrain structures, including the hippocampus, are required for learning, in addition to a brainstem-cerebellar circuit. The interstimulus interval (ISI) between CS onset and US onset is perhaps the most important factor in classical conditioning, but studies comparing delay and trace conditioning have typically not matched these procedures in this crucial factor, so it is often difficult to determine whether results are due to differences between delay and trace or to differences in ISI. In the current study, we employed a 580-ms CS-US interval for both delay and trace conditioning and compared hippocampal CA1 activity and cerebellar interpositus nucleus activity in order to determine whether a unique signature of trace conditioning exists in patterns of single-unit activity in either structure. Long-Evans rats were chronically implanted in either CA1 or interpositus with microwire electrodes and underwent either delay eyeblink conditioning, or trace eyeblink conditioning with a 300-ms trace period between CS offset and US onset. On trials with a CR in delay conditioning, CA1 pyramidal cells showed increases in activation (relative to a pre-CS baseline) during the CS-US period in sessions 1-4 that was attenuated by sessions 5-6. In contrast, on trials with a CR in trace conditioning, CA1 pyramidal cells did not show increases in activation during the CS-US period until sessions 5-6. In sessions 5-6, increases in activation were present only to the CS and not during the trace period. For rats with interpositus electrodes, activation of interpositus neurons on CR trials was present in all sessions in both delay and trace conditioning. However, activation was greater in trace compared to delay conditioning in the first half of the CS-US interval (during the trace CS) during early sessions of conditioning and, in later sessions of conditioning, activation was greater in the second half of the CS-US interval (during the trace interval). These results suggest that the pattern of hippocampal activation that differentiates trace from delay eyeblink conditioning is a slow buildup of activation to the CS, possibly representing encoding of CS duration or discrimination of the CS from the background context. Interpositus nucleus neurons show strong modeling of the eyeblink CR regardless of paradigm but show a changing pattern across conditioning that may be due to the necessary contributions of forebrain processing to trace conditioning.     

Role of the ultrasonic vocalization of the female rat (Rattus norvegicus) in sexual behavior

Both male and female rats vocalize ultrasonically during mating. Whereas male calls are known to facilitate female proceptive behavior, the female mating call has not been studied beyond spectrographic analysis. In this article, a series of experiments were done to examine the effects of the female's mating call on rat mating behavior. In the first experiment, females copulated with intact males before and after surgical devocalization. In the second experiment, intact females copulated twice with a male: once when they were able to hear and once when they were temporarily deafened with a medical ear mold. In the third experiment, tape recorded ultrasounds were placed in the presence of devocalized females while they were copulating with intact males. In the control condition, tape hiss was presented. In each experiment, it was observed that the female darted more if communication were disrupted (i.e., female devocalized or male deafened). Playback partially reduced darting to control levels. No other behavior was affected consistently across all experiments. Female calls might facilitate self-regulation of mating behavior, or they might focus the male's attention on her proceptive behaviors. It is also possible that the female calls could alter the stimulus properties of the male's behavior, indirectly affecting her own behavior.     

Neonatal androgenic stimulation and adult sexual behavior in male and female golden hamsters.

Neonatally and adult castrated male hamsters as well as neonatally androgenized and nonandrogenized female hamsters were tested for both mounting and lordosis behaviors during treatment with either testosterone or ovarian hormones. Neonatal androgenization facilitated mounting behavior in adult animals administered either testosterone or ovarian hormones and suppressed lordosis behavior in adult ovarian-hormone-treated animals. Early androgen effects on the display of lordosis behavior during adult testosterone treatment were complex and varied with the exact timing of perinatal endogenous or exogenous androgenization. Species differences in hormone-behavior relationships and the possible role of perinatal androgenization in the development of rodents' ability to aromatize androgens were discussed.     

Social isolation inhibits male-like sexual behavior in female hamsters

In the female golden hamster, Mesocricetus auratus, group housing permits the expression of male-like behavioral patterns including mounting and pelvic thrusting toward an estrous stimulus female. Sixty percent of females housed in groups of five showed these behaviors, while singly housed females were rarely observed to show mounting or thrusting. Females weaned at 19 or 35 days of age did not differ in their tendencies to show male-like behavioral patterns. Virtually all observations of mounting and pelvic thrusting behaviors were made on days when the females being tested were in behavioral estrus. These findings differ from previous studies which have reported that masculine behavioral patterns are rare in normal female hamsters. In previous studies females that were evaluated were typically not in behavioral estrus and were not housed for long periods of time with other intact females. Social factors interact with hormonal state to contribute to the expression of male-like behaviors in female hamsters.     

Hysterectomy-induced maternal behavior during pregnancy in the rat.

Hysterectomies were performed between the 10th and 19th day of pregnancy, and females were tested with pups for the onset of maternal behavior starting 0,24, 48, or 72 hr after surgery. Pups remained with the females overnight, and testing was repeated daily with fresh pups until females exhibited maternal behavior. Latencies for the onset of maternal behavior were shorter after hysterectomy on the 10th and 16th days of pregnancy than in intact pregnant females at the same stages of pregnancy; latencies became shorter, the later the termination of pregnancy. When the ovaries were removed along with hysterectomy during pregnancy, short-latency maternal behavior no longer was exhibited. Pregnant females were tested during the last 40 hr of pregnancy: nest building began at 34 hr prepartum and retrieving at 28 hr prepartum. The effect of hysterectomy during pregnancy on ovarian secretion of estrogen and progesterone is reviewed, and it is concluded that the rise in estrogen secretion, which follows hysterectomy during pregnancy, is most likely the cause of the rapid onset of maternal behavior after hysterectomy. A similar proposal is made for the prepartum onset of maternal behavior in intact pregnant females.