Induction of copulatory behavior in castrated female and male Arctic foxes.

The aim of the study was to test if it is possible to induce complete copulatory behavior in castrated Arctic foxes (Alopex lagopus) of both sexes for the purpose of other experiments. Two groups of castrated, sexually experienced Arctic foxes, four pairs in Experiment 1 (a pilot study) and eight pairs in Experiment 2, were treated with different regimes of hormone (estrogens and progesterone in females, testosterone in males). The animals were than tested for copulatory behavior. Nine out of 12 castrated bitches and 10 out of 12 castrated males displayed copulatory behavior during the season of reproductive quiescence for intact Arctic foxes. All the treatments induced complete copulatory behavior (i.e., copulation leading to locking) at least in some animals of both sexes. Examination of results for individual animals suggested that copulatory performance was influenced by preference for specific partners. Also the occurrence of copulation in an early test facilitated its reoccurrence on a later test in the same day with a different partner.

Role of the medial preoptic area in sexual behaviour of the male rat: a study using repeated cycloheximide infusions.

The effect of cycloheximide (CHX), an inhibitor of proteosynthesis, on sexual behaviour was studied in adult male rats in which it was infused into the medial preoptic area of the hypothalamus (MPOA). Sexual interaction took place under control and modification of the precopulatory behaviour of the female. Among the various bilaterally infused amounts of CHX--20 micrograms in 1 microliter, 40 micrograms in 1 microliter, 80 micrograms in 2 microliters--the effect of the largest dose corresponded to a hypothetical state of copulatory readiness of the males; 2 h after administration the males were not capable of initiating copulatory behaviour with a passively receptive female, but did so successfully with a highly soliciting female. The dependence of copulatory readiness of the males on the precopulatory behaviour of the females was confirmed repeatedly after this dose of CHX. At the same time, the precopulatory activity of the males towards a passively receptive female was unimpaired. The effect of CHX was reversible; 48 h after infusion the males displayed high copulatory readiness. Only half the males (n = 7) given bilateral infusions of 80 micrograms CHX fulfilled criterion of copulatory performance. Histological control demonstrated that the MPOA was affected bilaterally by CHX infusion in 10 males out of 14. The results are discussed from the aspect of participation of the MPOA in the regulation of male sexual behaviour. The method allows changes in sexual behaviour to be studied in the same individual in a chronic experiment.

Transition from precopulatory to copulatory behaviour in male rats with lesions in medial preoptic area: dependence on precopulatory pattern of female.

In the present study, both the precopulatory behaviour and the copulatory readiness of male rats following the bilateral medial preoptic area lesions was compared with their intact states. In behavioural testing, the intensity of female precopulatory behaviour was used as an experimental variable. The results showed that the natural threshold of copulatory readiness of males was increased in the lesioned state, the animals were more dependent on the soliciting patterns of the female. However, all the males exhibited conspicuous precopulatory behaviour towards the stimulus females used. Apparently, further brain structures participate in the regulation of sexual behaviour of males, above all, in activation or maintenance of precopulatory activity.

Effects of lisuride on precopulatory and copulatory behaviour of adult male rats.

Lisuride (12.5, 125, 250, 400, 600, 800 micrograms/kg) injected IP 40 min prior to observation of adult, but sexually inexperienced, male rats (a) caused a dose-dependent increase in motor activity, (b) suppressed rearing completely at doses of 125 micrograms/kg and above, and (c) caused a dose-dependent increase of specific sniffing of the scent traces of an estrous female, the sniffing lasting the whole duration of a 5-min test at 800 micrograms/kg. In the presence of a passively receptive (lordotic) female, the amount of time devoted to sniffing of the scent traces decreased but was still dose-dependent. The males exhibited relatively more precopulatory behaviour towards the female at 400-800 micrograms/kg. The number of males initiating copulatory behaviour was small and comparable with saline-injected controls. When exposed to sexual stimuli from a weakly soliciting (presenting posture) female the number of lisuride-treated males (250 and 400 micrograms/kg doses were used) initiating copulation was higher in comparison with the controls. At the same time the males began to copulate mostly with short latencies and without any precopulatory behaviour towards the female. The lisuride-treated males reached ejaculation after a very small number of intromissions. The effects of lisuride are discussed from the point of view of lowered behavioural thresholds of the males to specific and distinct stimuli.

Under what conditions does laboratory male rat initiate copulatory behaviour with passively receptive female.

Intact, adult male rats with a minimal copulatory experience acquired in interaction with fully proceptive (exhibiting ritualized dartings) female were tested at 1, 24, 48, 96 and 192 hour afterwards by means of passively receptive (responding with lordosis posture only) females. Only five males initiated copulations with lordotic females throughout the whole experiment. Because in the 192 hour test all the males copulated, the development of ability to initiate copulations could not be ascribed to the sexual experience only. Most probably, merely repeated exposition of the males to the passively receptive females resulted in the increase of the hormonal activity. The acquired ability of males to initiate copulations with thus behaviourally weak stimulus females persisted after sixty-four days of heterosexual abstinence. The observed variance in the latencies of the first intromission and in the number of incomplete mounts preceding the first intromission is interpreted in the sense of a parallel action of the processes of learning as well as of hormonal activation.

Initiation of copulatory behaviour in castrated male rats implanted with very small testosterone-filled silastic capsules.

Adult, sexually experienced male rats were castrated and two weeks later implanted with 5 or 10 mm long testosterone-filled silastic capsules (inner diameter 1.4 mm). From the seventh up to the fourteenth week following implantation the majority of males was found to be in the state at which they initiated copulatory behaviour with proceptive (darting) females but not with passively receptive (lordotic) females. Being in this state, their copulatory performance was comparable with precastration level except the decreased frequency of intromission befor the first ejaculation. As to the precopulatory behaviour, the males displayed it even towards females which did not stimulate copulatory behaviour in these males. In all the applied measures no difference between the 5 and 10 mm capsules was revealed. The used implants were found behaviourally effective about fourteen or nineteen weeks throughout following implantation or reimplantation, respectively.

The effect of bull seminal ribonuclease on reproductive organs and sexual behaviour in male rats.

Wistar male rats received an intratesticular injection (at 114 and 265 days of age) of 3 mg of partially purified bull seminal ribonuclease (AS RNase) or saline. It was found that sexual behaviour (initiation of copulation as well as copulatory behavioural pattern) of experimental males was not changed, but the ability of these males to fertilize females was evidently suppressed. In addition to significantly lower weights of testes and epididymis, inhibition of seminiferous epithelium development (aspermatogenesis) associated with the absence of spermatozoa was determined in cauda epididymidis in experimental animals. However, Leydig cells remained without changes. Plasma testosterone levels of AS RNase treated males were not altered in comparison with the controls. Thus AS RNase specifically impaired spermatogenesis but did not influence androgen action and sexual behaviour.

Stimuli eliciting sexual arousal in males who offend adult women: an experimental study.

The sexually arousing effects of short film scenes showing a naked actress's seductive behavior were phalloplethysmographically measured in 14 sexual deviates. These were males who had offended adult women, predominantly exhibitionists. Controls were 14 normal men. Deviates responded positively to the scenes and differentiated strong and weak seduction scenes similarly to normals. Consequently, the question arises of why deviates avoid their victim's erotic cooperation and why they do not offend their regular sexual partners. Post hoc analysis of five scenes which elicited a strikingly higher response in deviates than in normals suggested that these scenes contained reduced seductive behavior but unrestrained presentation of the genitals. This finding further encourages the laboratory study of stimulus conditions for abnormal sexual arousal which occurs during the sexual offense.

Variability of stimulus effect in the course of phallometric testing.

To study the serial effect in phallometric experiments, several sexual stimuli (film scenes) were presented in different orders to 56 subjects in four groups. All stimuli were presented at a relatively constant basal level of penile volume after the subjects' engagement in a nonsexual cognitive task. Serial effects occurred. At the beginning of the session, the magnitude of penile response did not depend on the content of sexual stimuli, the second stimulus eliciting a higher effect than the first. The differential effect of stimuli occurred only when they were shown in the third or fourth position. Finally, it was demonstrated that the effect of the stimulus depends to some extent on the effect of the preceding stimulus.