Mount Latency Research Articles

Interaction of hunger and sexual motivation in the male rat: A time-sharing approach

To examine the interaction of hunger and sexual motivation, male rats were given sexual behaviour tests under 0, 24, and 48 h of food deprivation. Each male was placed with an oestrous-induced female and allowed to copulate until sexual exhaustion. Food was freely available throughout the test period. Mount and intromission latencies increased under both levels of food deprivation, but neither ejaculation frequency nor any of the other fourteen measures of sexual behaviour were altered under deprivation conditions. There was a decreased latency to start eating, an increase in time spent eating, and an increase in the amount of food eaten with increased food deprivation. The frequency of feeding bouts increased, but the duration of feeding bouts was constant over deprivation conditions. Under food deprivation, animals shifted from sexual behaviour to feeding more frequently than when they were non-deprived. These shifts occurred primarily during periods of low sexual arousal. The majority of feeding occurred during the post-ejaculatory intervals. Bouts of sexual behaviour were not usually interrupted by bouts of feeding. This pattern suggests that feeding and sexual activity occur on a time-sharing basis with sexual behaviour as the dominant activity.

Facilitation by opiate antagonists of sexual performance in the male rat.

Intraperitoneal administration of increasing doses (5 mg/kg or 20 mg/kg) of the opiate antagonists naloxone hydrochloride or naltrexone hydrochloride to sexually experienced male rats caused a significant reduction in the number of intromissions prior to ejaculation and ejaculation latency. Mount and intromission latencies were significantly reduced following treatment with only the lower dose of each antagonist. Ways are suggested whereby endorphins may modulate masculine sexual performance and thereby contribute to successful fertilization of female conspecifics.

Amygdaloid hypersexuality in male cats re-examined

It is widely believed that amygdaloid lesions induce hypersexuality in certain mammals including humans. However, the evidence is so confused as to obscure the real nature of the purported changes. Twelve sexually experienced male cats were given two series of quantitative tests, the conventional sex test and a new selection test in which the animals were presented sequentially with a small stuffed toy panda, moving toy, tranquilized rabbit, tranquilized male and estrous female. Lesions in 8 experimental males were largely confined to the basolateral nuclei and periamygdaloid cortex. In the standard test and in the response to the female in the selection tests, the only significant postoperative change in the major measurements of sexual behavior was a decline in initial mount latency. However, in the selection tests, the major change was an increased tendency to mount less appropriate objects. There was no evidence of hypersexuality, in the sense of a higher level of sexual performance. This change was not interpreted as the disruption of an amygdaloid mechanism directly regulating sexual behavior, but rather as interference with a system which normally modulates approach and withdrawal behavior in response to stimuli that are salient with respect to an existing behavioral setting and set.

Acute changes in plasma testosterone levels and their relation to measures of sexual behaviour in the male house mouse ( Mus musculus)

There is an increasing amount of evidence, from several mammalian species, that plasma testosterone levels increase acutely when the male is exposed to sexual stimuli. Work reported here investigates whether such responses occur in male mice, and whether their incidence is related to measures of sexual behaviour. Close proximity of oestrous female mice was found to result in increased plasma testosterone levels in some strains within 15 min. Immediately after a sexual behaviour test, plasma testosterone levels were higher in males showing sexual responses. There were correlations between testosterone levels and mount latency, but none with ejaculation latency. Testosterone levels were greatest at the initiation of mounting responses, and declined during copulation, although not significantly.

Potency in Male Rhesus Monkeys: Effects of Continuously Receptive Females

Ejaculations decreased and mount latencies increased when intact males were paired regularly over a 3.5-year period (3180 tests) with ovariectomized females made constantly receptive by daily injections of estradiol. The deterioration in potency was abruptly and completely reversed by substituting a group of new but similarly treated females for the original ones.

Mating in male rabbits after anesthesia of the glans penis

Desensitization of the glans penis with a local anesthetic (Lidocaine paste) in sexually experienced male rabbits decreased intromission frequency, lengthened intromission latencies and postejaculatory intervals. Mount frequency and mount latency remained unchaned. The decrease in intromission frequency was not due to an inability to achieve erection but rather to a failure to execute the deep pelvic thrust associated with intromission. Unlike rats and cats, the rabbit glans penis was found to have no spines.

Olfactory deprivation and mating behavior in sexually experienced male cats

The effects of bilateral olfactory bulbectomy (sodium pentobarbital anesthesia) upon mating behavior was studied in sexually experienced adult male cats. In the first experiment preoperative and postoperative behavior of eight animals were compared. After bulbectomy there were no decrements in mating behavior; rather, small but significant increases in sexual activity occurred, e.g., increased frequency and duration of intromission, decreased initial and intromissive mount latencies. A second experiment was designed to test the hypothesis that this increase in sexual activity resulted from a decrease in the amount of test time that the desensitized animals spent in related activities, especially sniffing. Here sniffing, grooming and scratching were measured in five bulbectomized and four sham operates. They were tested preoperatively, postoperatively in the usual test room and later in a strange test room. The same increase in sexual behavior appeared in the bulbectomized animals as in the first experiment. Additionally, there were significant decreases in frequency and duration of sniffing the room and sniffing the female. The sham operates remained unchanged. When tested in a strange room the shams reacted with a decrease in frequency of intromission and an increase in initial mount and intromissive mount latencies. Sniffing the room rose to well above preoperative levels. Under similar conditions the bulbectomized males showed some increase in frequency of intromission, increased latencies and an increase in sniffing of the room, but not to preoperative levels. The probability that complete anosmia was achieved in these experiments is supported by detailed histological examination of the brains which demonstrated that the glomeruli in remaining bulbar fragments were all markedly degenerate. Other important histological changes are described. The results are discussed in relation to the pronounced decrements following bulbectomy in several species of rodents.

Disruption of copulation in male rats after hypothalamic lesions: A behavioral, anatomical and neurochemical analysis

Lesions of the medial forebrain bundle (MFB) in the middle and posterior hypothalamus disrupted copulatory behavior of the male rat. Detailed behavioral, anatomical and biochemical analyses of lesion effects yielded the following conclusions: (1) MFB lesions interfered with the initiation but not with the execution of copulation. This conclusion is based on the findings that lesioned animals either failed to copulate, or copulated after prolonged first mount and intromission latencies. Once the first copulatory response was achieved in a given test, ejaculations followed at a normal rate. (2) MFB lesions in the middle hypothalamus and lesions extending above the MFB in the posterior hypothalamus were more effective in disrupting copulation than ventrocaudal lesions. The results suggest that as the posterior hypothalamus is approached, a significant proportion of fibers responsible for producing the copulatory deficit leave the MFB in a dorsal direction. (3) The severity of the copulatory deficit was significantly related to telencephalic norepinephrine (NE) depletion but not to serotonin depletion. These results together with the anatomical distribution of effective lesion placements suggest that a dorsal ascending NE bundle, previously identified by histochemical fluorescence methods, may be a factor in the sexual effects of MFB lesions. However exceptions inthe data raise serious questions regarding any hypothesis which proposes that the degree of sexual deficit is directly and exclusively related to total level of telencephalic NE depletion.

Alteration in the sexual behaviour of male and female rats after neonatal administration of p-chlorophenylalanine

p-Chlorophenylalanine (pCPA) was administered to male and female rats on the 2nd and 3rd (20 mg/kg) and on the 5th and 6th (100 mg/kg) postnatal day. The display of spontaneous and hormone induced adult sexual behaviour, the onset of puberty in the females, and the effect of the neonatal drug injections on serotonin and 5-hydroxyindole acetic acid levels in the brains of 15-day-old rats were examined. In the females, the time of vaginal opening was delayed even though the vaginal cytological cycles appeared to be normal. In addition, these females showed less ear wiggling activity during both spontaneous and hormone induced copulatory behaviour and a tendency to shortening of mount latencies during hormone induced masculine sexual behaviour. The drug treated males were, as adults, generally more sexually facile than were the vehicle treated controls: they required fewer mounts and intromissions prior to ejaculation, and displayed shorter intromission and ejaculation latencies as well as shorter refractory periods and intervals between successive intromissions. The hormone induced female sexual behaviour in the drug treated males appeared, however, to be unaltered. Finally, although many differences in adult sexual behaviour were observed in the animals treated with pCPA shortly after birth, no changes or sex differences in hypothalamic or forebrain concentrations of serotonin or 5-hydroxyindole acetic acid were found in animals treated similarly in infancy but killed at the age of 15 days. The relevance of these findings is discussed in the light of the possible significance of brain indole amines during the sexual development and differentiation.

Copulatory behaviour of rats ( Rattus norvegicus) as a function of prior copulatory experience

Two experiments were reported which were designed further to elaborate the contributions of prior copulatory experience to copulatory behaviour in rats. In experiment 1—test 4 the behaviour of two groups of rats of equal age with 0 or 3 prior tests were compared. In experiment 1—test 7, performance of rats with 0, 3, or 6 prior tests was compared. In experiment 2 performance of rats with 0 or 4 prior tests was compared. Data were related to those of Larsson (1959). Prior copulatory experience produced small, but generally reliable, decreases in mount, intromission, and ejaculation latencies. Intromission rates were generally increased. There was some trend for decreased mount and intromission frequencies. The effect of experience on postejaculatory intervals was a weak one. The prediction of differential effects of experience on measures controlled by Beach's hypothetical Arousal Mechanism and Copulatory Mechanism was not borne out.

Effects of hippocampal lesions on the copulatory behavior of male rats

Abstract Performance on two preoperative and two postoperative copulation tests was compared for male rats given total hippocampal, dorsal hippocampal, neocortical, and no lesions. Eight rats were in each group. Tests were continued to a satiety criterion. Statistically significant increases in Mount Latency and Intromission Latency were found in the rats with total hippocampal lesions. There were no other significant differences.

Behavioural biology of the collared lemming Dicrostonyx groenlandicus (Traill): II. Sexual behaviour

The motor patterns associated with copulation in captive collared lemmings is studied. Eight male acts and six characteristic of the female in a sexual encounter were denned. These acts were then recorded quantitatively in a series of 10-min tests performed on ten experienced pairs. The pairs were observed when females were in dioestrus and when they were in oestrus. Comparison of time scores and frequencies revealed significant differences in male acts, e.g. longer duration for allo-groom and perineal investigation and higher frequency for perineal investigation when females were in dioestrus; longer duration and higher frequency scores for mount, thrust, ejaculation and auto-groom perineum when females were in oestrus. Females scored significantly longer durations of auto-groom, mounting and lordosis while in oestrus. In these 10-min tests with oestrous females the ten males displayed considerable individual variability in measures of latency to mount, thrust, ejaculate and in number of bouts of thrust per ejaculation. Ten pairs of lemmings were subjected to 1-hr tests in which females were in oestrus. In terms of number of ejaculations achieved, males sorted out into four classes, i.e. three ejaculated once, five twice, one three times and one four times. For multiple-ejaculating males, the number of bouts of thrust, latency scores for successive episodes of ejaculation and post-ejaculation mount latencies all increased with successive ejaculations. These data are discussed in terms of the intrinsic importance of the measures of reproduction in the collared lemming. The possible relevance of certain aspects of female behaviour to reproduction in feral lemmings is considered.

Studies of mating behaviour and some factors influencing the sexual response in the male sheep Ovis aries

Close observations of mating in sheep indicated that in 50 matings only three intromissions occurred without ejaculation and these were accompanied by weak thrusts. The following observations were recorded during sexual exhaustion studies in which rams were individually mated with receptive females until no mounts occurred within a 20-minute period. Total number of ejaculations averaged from 2·9 to 8·4 for individual rams with an overall average of 5·5 and a mode of 4. Number of mounts per ejaculation averaged from 1·3 to 3·2 for individual rams with an overall average of 1·6 and a mode of 1. Initial mount latencies averaged from 0·25 to 0·74 minutes for individual rams with an overall average of 0·44 minutes with a mode of 0·20 to 0·30 minutes. Post-ejaculatory intervals increased regularly with succeeding ejaculations. The coefficient of correlations between total number of ejaculations and initial mount latencies or first post-ejaculatory interval were 0·16 and 0·45, respectively. Following ‘sexual exhaustion’, exposing the rams to a different not recently mated female resulted in reinitiation of mating at or near original levels. Exposing the rams to a different recently mated female following ‘sexual exhaustion’ did not result in a significantly greater number of ejaculations than that observed when the same female was returned. Returning the same ewe at various time intervals following sexual exhaustion indicated that sexual responsiveness increased rapidly in a few hours. A return to complete sexual responsiveness to this same female, however, could not be demonstrated even after 2 weeks. Electro-ejaculation had no effect upon subsequent sexual performance.

The effect of neonatal hyperoxia on sexual arousal and emotionality in the male rat

Neonatal hyperoxia was studied as a method of provoking behavioural disturbances in animals because of its possible connection with adaptive deficiencies observed in premature human infants who had been exposed to excessive O 2 at birth. The sexual responsiveness and emotionality of adult rats was measured after they had been subjected to hyperoxia for 10 days after birth. These Ss were found to be less sexually responsive (longer mount latencies and smaller percentage of mounters) and more emotional (more defecation in the open field apparatus, larger adrenals, and smaller body weights) than untreated controls. Two other control groups of blinded and blinded plus O 2 treated Ss yielded comparable patterns to the O 2 group. These findings were interpreted to indicate that neonatal hyperoxia could be a potent influence on some aspects of adaptive behaviour and that at least one of its consequences was to establish long term stress factors which were apparently also introduced by the other treatments.