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PubMed1988

Old age and sexual exhaustion in male rhesus macaques.

The capacity for multiple ejaculations was measured in three groups of rhesus macaques whose ages ranged from 9 to 30 years. Each male was given a test of sexual exhaustion with each of five ovariectomized, estrogen treated females. Sexual exhaustion was defined as a 45-min period without a mount when the males were paired with a female. None of the very old males (25-30 years, N = 4) achieved more than two ejaculations before reaching sexual exhaustion. Old males (19-20 years, N = 5) displayed as many as six ejaculations and fully adult (9-15 years, N = 5) males achieved a maximum of five ejaculations before meeting the criterion of sexual exhaustion. Although very old males mounted as often as younger males they achieved fewer intromissions and the latency to intromission and ejaculation was longer. Mean mount and ejaculation latencies and the postejaculatory interval increased after ejaculation in all age groups. The females were not equally attractive sexually to the males and very old males were especially selective, copulating with only three of the females.

Aging↗
PubMed1988

Higher CNS control of penile responses in rats: the effect of hypothalamic stimulation.

The effect of electrical stimulation of the medial preoptic area (MPOA) of the hypothalamus on penile responses in rats was investigated. No females were present and penile responses were observed through the use of an inclined mirror. MPOA stimulation was found to elicit two types of penile responses: penile movement within the sheath and protrusion of the penis outside the penile sheath. While these responses also occurred spontaneously during the nonstimulation control sessions, they occurred in significantly higher frequencies following MPOA stimulation. The results also produced an unexpected finding. While studies on the effect of hypothalamic stimulation on copulation show stimulation-bound effects, MPOA stimulation in the absence of a receptive female consistently triggered penile responses as a poststimulation effect.

Animals↗
PubMed1989

Peptidergic control of male rat sexual behavior: the effects of intracerebral injections of substance P and cholecystokinin.

Behavioral experiments examined the roles of substance P (SP) and cholecystokinin (CCK) in male rat copulatory behavior. Male copulatory behavior was recorded subsequent to injections of different doses of CCK and SP into the medial preoptic-anterior-hypothalamic area (MPOA-AH), caudate/putamen (CP), or the lateral ventricles (LV) in sexually experienced male rats. In the first experiment, three different doses of SP (10, 100, and 200 ng/cannula) injected bilaterally into the MPOA-AH produced marked changes in several components of male copulatory behavior. Latencies were most affected. All three doses significantly shortened the interval to initiate copulation, and the 10 and 100 ng, but not 200 ng dose also significantly reduced ejaculation latencies. Injections of 10 ng of SP into the CP did not affect sexual behavior, while injections into the LV produced changes different from those of MPOA-AH injections. These data argue for some degree of site specificity of the effects of the MPOA-AH injections. Bilateral injections of 10 ng of SP into the MPOA-AH, were incapable of inducing copulatory behavior in castrated rats deprived of testosterone. Injections of an undiluted SP antiserum (2 microliters/cannula) into the MPOA-AH produced a dramatic impairment of male copulatory behavior. These injections significantly lengthened amount, intromission, and ejaculation latencies, while having no effect on the number of mounts or intromissions prior to ejaculation. In contrast, bilateral injections of CCK-8 (10, 100, and 200 ng/cannula) into the MPOA-AH failed to affect any parameter of male copulatory behavior.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1989

Environmental influences on masculine sexual behavior in mice.

Retention of masculine copulatory behaviors following castration varies among B6D2F1 male mice. In the present study, we examined the effect of test environment and the amount of behavioral testing after castration, on retention of copulatory responses in castrated B6D2F1 male mice. Results showed that weekly behavioral testing after castration was not necessary for the retention of ejaculatory reflexes. However, the test environment had a major effect. Following castration, 26% of the males completely stopped showing ejaculatory responses when tested in the test arenas. When these males were tested in their home cages, 75% achieved at least one ejaculatory response in four home cage tests. Castrated males that continued to copulate in the test arena situation also achieved ejaculatory reflexes in their home cages. These results indicate that for some B6D2F1 males, the retention of sexual behaviors after castration is influenced by environmental factors.

Animals↗
PubMed1989

Embryonic sex steroids affect mating behavior and plasma LH in adult chickens.

Chicken embryos of both sexes were treated with either antiestrogen (tamoxifen = T), antiandrogen (flutamide = F), aromatization inhibitor (ATD = A), estradiol (E), or oil (control = C). Before puberty, some males of each group were castrated. At puberty, birds were tested under the following regimes: castrated males injected daily with testosterone propionate (CAS + TP) or estradiol benzoate (CAS + EB), intact males (M-INT), intact females (F-INT), and females injected daily with TP (F-TP). In the M-INT and CAS + TP males, E treatment suppressed masculine mating behavior. The embryonic treatments with T, F, and A demasculinized only the frequency of copulations. None of the antihormone treatments caused any masculinization of the sexual activity in the F-TP birds. Untreated males had higher plasma LH than females. The embryonic treatment with E reduced (feminized) the LH levels in CAS + EB birds. This effect was less pronounced in M-INT birds. The results suggest that in chickens, estradiol plays a role in the masculinization of copulatory behavior potential in the developing male embryo. High embryonic estradiol reduces the potential for displaying male sexual behavior at puberty. Feminization of LH secretion requires a high level of estradiol in both embryonic and adult life.

Androstatrienes↗
PubMed1989

Level searching: a new assay of sexual motivation in the male rat.

Mendelson and Gorzalka recently described a bilevel chamber for the evaluation of rodent sexual behavior. In initial studies it was observed that during 5 min adaptation periods prior to the introduction of a sexually receptive female rat, male rats with prior sexual experience in these chambers would move from level to level in apparent search for the female rat. In Experiment 1, we examined the acquisition of this level searching behavior in male rats. Sexually active male rats were given access to either sexually receptive or nonreceptive female rats following a 5 min period alone in the bilevel chamber. Only male rats that pursued and copulated to ejaculation with sexually receptive females in the bilevel chamber significantly increased the number of their level to level movements in subsequent tests during the 5 min periods prior to the introduction of the female rat. In Experiment 2, male rats that had acquired asymptotic rates of level searching showed a significant attenuation of this behavior when the presentation of a female rat into the chamber was discontinued. These findings lead us to conclude that the increase in level to level movement by the male rat represents a sexually motivated search for the female rat. We suggest that the analysis of the acquisition, maintenance, and extinction of level searching behavior might serve as a simple assay of sexual motivation in the male rat.

Animals↗
PubMed1989

Changes in forebrain Na,K-ATPase activity and serum hormone levels during sexual behavior in male rats.

We have previously shown that Na,K-ATPase activity (the enzymatic machinery for the sodium pump) in brain areas such as the medial basal hypothalamus (MBH) and the preoptic-suprachiasmatic region (POSC) can be changed by experimental manipulations of gonadal function. We now report enzyme levels in brain regions as related to hormonal changes occurring during sexual behavior. Male rats were exposed to receptive females and decapitated immediately after displaying one of the following behavioral events: the start of copulatory activity, first ejaculation, and the beginning of a second copulatory series. A group of noncopulating animals were used as control. The variables measured included serum levels of LH, PRL and testosterone and Na,K-ATPase activity in MBH, POSC and parietal cerebral cortex (CC). A steady increase in enzyme activity in the POSC, but not the MBH or CC, was found in copulating animals. Serum LH levels changed in a similar fashion. A sharp increase in serum PRL levels, seemingly related to ejaculation, was also observed. These data are consistent with our previous findings on monoaminergic neurotransmission in brain regions related to male sexual behavior.

Animals↗
PubMed1989

Vomeronasal organ removal and female mouse aggression: the role of experience.

Removal of the vomeronasal organ (VNX) from female mice had little effect upon fecundity, nest building and pup retrieval. Surprisingly, VNX significantly affected aggression by lactating females. Normally, lactating females will attack and fight intruders placed into the home cage, especially if the intruder is an unfamiliar male. In Experiment 1, we determined that VNX prior to sexual experience totally eliminated this type of aggression. Intact females were highly aggressive, but much more so to unfamiliar than to familiar males. Copulation prior to surgery did not ameliorate the effects of VNX; again, none of the VNX females were aggressive (Experiment 2). In Experiment 3, attacks and fights by previously aggressive primiparous females also were eliminated or significantly suppressed following VNX. Even when the testing occurred later during the postpartum period and for extended periods of time, this same suppression of aggression held following VNX. We conclude that aggression by lactating female mice is under strict mediation by chemosignals detected by the vomeronasal organ.

Aggression↗
PubMed1990

Postimplantation pregnancy disruptions in meadow voles: relationship to variation in male sexual and aggressive behavior.

Previous research on Microtines indicates that the presence of new males may more effectively produce pregnancy disruptions than do pheromones alone. If the male's presence is important, behavioral differences among males may be related to the occurrence of disruptions. We observed female meadow voles (Microtus pennsylvanicus) interacting with new males twelve days after they had been paired with stud males. Behavioral interactions were recorded for one hour on each of Days 12-14. Timing of parturition and weight gain by Day 12 were used to assess whether a disruption had occurred. Females with disrupted pregnancies were frequently observed mating within an hour of being placed with the new male, whereas females that retained their original pregnancies rarely copulated with the new male. When pregnancies were disrupted, female-new male pairs fought more, but also engaged in more nonaggressive contact than when pregnancies were retained. Pup survival and male attendance of pups were lower when females retained litters, suggesting that females could successfully rear more pups if the original pregnancy was reabsorbed. However, relatively aggressive females paired with nonaggressive new males protected retained litters from new males. New males were tested for aggressive and pup care responses to an unrelated pup on the day before they were placed with the females. Males aggressive to unrelated pups in these tests were also more aggressive to females on Day 12. These data suggest that male aggressiveness may signal females when it would be advantageous to disrupt pregnancy.

Aggression↗
PubMed1990

Pinealectomy prevents short photoperiod inhibition of male hamster sexual behavior.

The role of the pineal gland in mediating photoperiodic influences on copulatory behavior (CB) of male hamsters (Mesocricetus auratus) was assessed in the presence and absence of testosterone (T). The results demonstrate that the pineal gland is necessary for short photoperiod exposure to alter CB. Sexually experienced males were exposed to either long (14L:10D; LP) or short (8L:16D; SP) photoperiods for 13 weeks; after the first 2 weeks of exposure, all animals were castrated and then either pinealectomized (PINX) or sham operated (SHAM PINX). CB tests over an 8-week period following surgery indicated that copulatory impairments developed in all animals, but deficits occurred more rapidly among short photoperiod males with intact pineal glands (SP-SHAM PINX), compared to pinealectomized males housed in either the long (LP-PINX) or short photoperiod (SP-PINX). LP-PINX and SP-PINX animals were not statistically different on any of the CB measures examined. Nine weeks after castration (11 weeks of photoperiod exposure), all hamsters were given a T-filled Silastic capsule to restore CB. Restoration of sexual behavior was less rapid and less complete among SP-SHAM PINX hamsters. Additionally, males in this group took longer to initiate copulation relative to the pinealectomized hamsters. These findings are compared to other reports suggesting that photoperiodic effects on the sexual behavior of female hamsters do not require an intact pineal gland.

Animals↗
PubMed1991

Twenty-two kHz alarm cries to presentation of a predator, by laboratory rats living in visible burrow systems.

When a cat was presented to groups of 3 male and 2 female laboratory rats in the open area of a visible burrow system, the rats retreated to the burrow system and showed high levels of 18-24 kHz ultrasonic cries during the cat presentation and for 30 min following removal of the cat. Latency to make ultrasonic vocalizations, durations of these vocalizations, and duration in the burrow systems were all strikingly and reliably different during and after cat exposure in comparison to similar periods with a control (stuffed cat toy) stimulus. However, when individual rats were exposed to a cat in an open area of similar size, ultrasonic cry production was minimal. Also rats exposed individually to a cat in an apparatus providing an escape chamber similarly showed no ultrasonic cries, indicating that concealment per se is not a sufficient condition for their appearance. These results suggest that the production of ultrasonic vocalizations during and after exposure to a predator is greatly facilitated by the presence of familiar conspecifics, and may serve as alarm cries. While the alarm cry hypothesis also suggests a possible function for 18-24 kHz ultrasounds in the context of copulation and intraspecies aggression, the sonographic and functional relationships among the cries emitted in these different situations remain to be analyzed.

Animals↗
PubMed1992

Place conditioning reveals the rewarding aspect of social interaction in juvenile rats.

Rewards, as diverse as food, sweetened solutions, copulation, electrical brain stimulation, and drugs abused by humans, have been shown to condition place preferences in rats. Juvenile rats will readily learn to traverse a T-maze for the opportunity to interact with another similar-aged rat. This suggests that play behavior is rewarding. Experiment 1 examined whether play (as quantified by rough-and-tumble pinning) would act as a sufficient reward to condition a place preference (CPP). Experiment 2 examined whether pairings with a nonplaying partner would decrease the time spent in the preferred side and thus suggest a conditioned place aversion (CPA). In Experiment 1, dominant juvenile rats were given free access to a CPP apparatus and a side preference for one of the two physically distinct sides was determined. Dominant rats were then conditioned twice daily over four days in the CPP apparatus. They spent their first session confined in their preferred side with a scopolamine-treated partner (that rendered the partner unable to respond to play solicitations) and during the second session, dominant rats were confined to their less preferred side with a submissive play partner. The number of dorsal contacts, as well as frequency and duration of pinning, were recorded. Following conditioning, side preference was redetermined. A similar procedure was used in Experiment 2 except that the subjects underwent conditioning on their less-preferred side without a play partner. Results of Experiment 1 demonstrated that the dominant rats significantly increased (198.6%) the time spent on the originally less-preferred side after play conditioning.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

Age-dependent variations in the sexual preference of male rats.

Male rats were tested for their sexual preference behavior at either 37, 70, 90, or 150 days of age on three different occasions; while still sexually naive, after sexual experience with a receptive female, and while sexually aroused by having initiated copulation. These tests resulted in the following findings: a) 37-day-old sexually naive males showed a preference for other males and failed to show a preference for either sex after exposure to females; b) 70- and 90-day-old males showed a statistically significant preference for the female after acquiring sexual experience; c) 150-day-old animals showed a female-oriented preference only after being sexually aroused with two intromissions preceding the preference test, and d) none of the age groups tested showed a female-oriented preference without previous exposure to females. It was then concluded that a) female-oriented behavior requires sexual experience and b) the effects of experience varies with age.

Aging↗
PubMedDate not supplied

Estradiol, but not dihydrotestosterone, in the medial amygdala facilitates male hamster sex behavior.

In the male Syrian hamster, the medial amygdaloid nucleus (Me) and medial preoptic area (MPOA) are critical for expression of male mating behavior. These regions contain steroid receptor-containing neurons that transduce hormonal signals essential for copulation. In castrated males bearing an intracerebral steroid implant in the MPOA, testosterone or estradiol can facilitate sexual activity. However, DHT is without effect. Testosterone can also stimulate mating when implanted in the Me. The present study determined if estradiol or DHT had behavioral activity in the Me. Twenty adult male hamsters were selected for vigorous sexual behavior. Twelve weeks after castration, sexual behavior was assessed and each male received a single intracranial implant (23-gauge tubing packed with crystalline estradiol or DHT, n = 10 each) placed stereotaxically into posterior Me (MeP). Behavior was examined after surgery to determine if androgens or estrogens in MeP could stimulate sexual behavior above that observed after castration. Mating behavior in DHT-implanted males was not significantly different from castrates. However, males with estradiol implants displayed significantly more copulatory and noncopulatory sexual activity after surgery compared to males with DHT implants. These results suggest that testosterone facilitation of mating behavior in MeP is mediated by aromatization to estradiol, and that DHT is not behaviorally active in this nucleus.

Amygdala↗
PubMed1984

Evaluation of the effect of BAL (2,3-dimercaptopropanol) on arsenite-induced teratogenesis in mice.

The effect of the chelating agent dimercaprol (BAL) on the embryotoxic and teratogenic effects of arsenite (As3+) was determined. BAL (sc, 30 mg/kg) was administered to pregnant CD-1 mice, either 8 and 4 hr prior to or 4 and 8 hr after a 12-mg/kg ip dose of arsenite; other females received a single sc injection of 60 mg/kg BAL concurrently with the arsenite. Treatments were given on Gestation Day 9 or 12 (copulation plug = Day 1). Controls received sc corn oil or ip H2O, with or without arsenite or BAL. Arsenite treatment caused gross and skeletal malformations and prenatal deaths, while controls were unaffected. When BAL was given prior to arsenite on Day 9, incidences of prenatal mortality and skeletal malformation were significantly diminished, and on Day 12, BAL protected against fetocidal effects of arsenite when given concurrently with the arsenite. No other significant protective effects against arsenite toxicity were seen due to BAL; however, concurrent BAL treatment on Day 9 appeared to result in decreased fetal mortality and a decline in skeletal malformations. BAL given following arsenite on Day 9 afforded no significant protection against the arsenic, although an apparent decrease in gross and skeletal malformations was suggestive of such an effect. According to these results, BAL is unlikely to have a practical beneficial effect on the arsenite exposed conceptus, because it must be administered prior to the teratogen (or perhaps simultaneously with it) to be effective.

Animals↗
PubMed1984

Two-year toxicity/carcinogenicity study of fresh-brewed coffee in rats initially exposed in utero.

Fresh-brewed regular coffee at concentrations of 25, 50, and 100% was consumed ad libitum as the sole fluid intake of F1 Sprague-Dawley rats (55 male and 55 female/group), derived from P0-treated females which were provided 50% coffee for about 5 weeks prior to copulation and throughout gestation and lactation. P0 males, P0 control females, and two groups of F1 control rats received tap water. Ten rats/sex/level were killed and examined after 1 year; survivors were killed after 2 years. Smaller mean body weights (50 and 100% coffee concentrations) occurred with increased feed and liquid consumption. Mean serum alkaline phosphatase, bilirubin, BUN, and calcium values occasionally were elevated. Serum cholesterol levels at 2 years were elevated in males (25 and 100%) and at 1 and 2 years in females (100%). Bone calcium was slightly reduced in females consuming 25 or 100% coffee for 1 year, but not after 2 years. Treatment-related increases in relative weights of lungs, kidneys, liver, and epididymides were recorded. Significantly increased mortality was observed in females receiving 50 or 100% coffee. There also was some evidence of a relationship between coffee consumption and the number of primary tumor-bearing animals; however, this finding appeared ambiguous, dependent on the assumption that tumors were the probable cause of death.

Abnormalities, Drug-Induced↗
PubMed1988

The relationship of embryotoxicity to disposition of 2-methoxyethanol in mice.

Paw development of CD-1 mice is uniquely sensitive to 2-methoxyethanol (ME) given by gavage (po) on gestation day (gd) 11 (copulation plug day = gd 0). The relation between induction of paw dysmorphogenesis and disposition of po ME (3.3 or 4.6 mmol/kg) in the maternal and conceptus compartments was investigated. The expression of digit malformations depends on metabolism of ME to methoxyacetic acid (MAA). ME and MAA were equipotent in causing teratogenicity. Alcohol dehydrogenase (ADH) catalyzes the initial rate-limiting oxidation that leads to embryotoxicity. The ADH inhibitor 4-methylpyrazole (0.12 or 1.2 mmol/kg) or ethanol (43.3 mmol/kg, single dose concomitant with ME or additional ethanol 5 and 10 hr later) reduced the incidence of malformations 60-100%, depending on the dosing regimen. Elimination of 14C from 1,2-14C-ME occurred predominantly via urine where 80% of a teratogenic dose was excreted and 6% appeared in CO2. Oxidation of ME to MAA was nearly complete after 1 hr when approximately 90% of 14C in maternal plasma and conceptus coeluted with authentic 14C-MAA upon HPLC. 14C-MAA levels in embryos were 1.2 X those in plasma 1 and 6 hr after dosing, although by 6 hr concentrations had declined to approximately 50% of 1-hr values. Concomitant ethanol did not affect 14C kinetics as measured in maternal blood after oral 14C-ME, but retarded ME conversion to MAA by about 2 hr. Furthermore, embryo 14C-MAA levels then reached only 50% of the peak in embryos from dams dosed with ME alone, an effect that coincided with less 14C incorporation into macromolecules synthesized by the embryo within 6 hr. These data imply that the attenuation of digit malformations by concomitant ethanol may be explained by changes in MAA disposition. However, delayed ethanol (5 and 10 hr after 3.3 mmol ME/kg) reduced teratogenicity by 25%, although MAA was present in the embryo up to 5 hr. Dams given 14C-MAA by iv injection had higher 14C blood levels than after MAA po but their offspring had fewer digit malformations. Peak and steady-state plasma levels of MAA as well as embryo concentrations of the chemical do not appear to determine the embryotoxic outcome whereas further metabolism of MAA does.

Abnormalities, Drug-Induced↗
PubMed1976

Intracranial cycloheximide: effect on male mouse sexual behavior and plasma testosterone.

Cycloheximide (Cyclo), an inhibitor of protein synthesis, infused bilaterally into the preoptic area (POA) of intact B6D2F male mice significantly inhibited male sexual behavior when the males were presented with receptive females 12 hr after treatment. The few males that ejaculated appeared to copulate normally. This finding suggests that Cyclo acts primarily by inhibiting sexual arousal rather than sexual performance. The inhibition of sexual behavior was not observed when the males were tested 84 hr after treatment. After exposure to an estrous female, plasma testosterone levels were measured in males with POA infusions of Cyclo or saline vehicle. No significant difference was found, but both groups had significantly higher levels of plasma testosterone than males not exposed to estrous females. It is suggested that the interference with sexual behavior by Cyclo was not due to interference with the neuroendocrine mechanisms controlling blood andorgen levels, but due to Cyclo acting directly on the neural circuits controlling sexual responsiveness.

Animals↗