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PubMed1981

Sexual behavior decreases pain sensitivity and stimulated endogenous opioids in male rats.

In male rats copulation has antinociceptive effects as measured either by shock-induced vocalizations or hindlimb withdrawal to pinch. Prolonged mating reduces the content of endogenous opioids in midbrain but not in hypothalamus or caudate nucleus. Blockage of opiate receptors with the narcotic antagonist naloxone (4 mg/kg) significantly extends the postejaculatory interval. The results indicate that mating is a biological stimulus for the release of endogenous opoids, possibly to (a) prevent intense sexual stimulation from becoming aversive, and (b) increase its reward value.

Analgesia↗

PubMed1993

5-HT1A and 5-HT1C/1D receptor agonists produce reciprocal effects on male sexual behavior of rhesus monkeys.

Research has indicated that serotonin (5-HT) is involved in regulating male sexual behavior in rodent, as well as primate species. The present study was designed to further characterize 5-HT influences on male sexual behavior of rhesus monkeys. Experiment 1 examined the effects of 5-HT1A and 5-HT1C/1D receptor stimulation on penile erections and yawning behavior. Administration of the 5-HT1C/1D receptor agonist, m-chlorophenylpiperazine (m-CPP, 0.8 and 3.0 mg/kg), facilitated the occurrence of penile erection, and at doses greater than 0.2 mg/kg stimulated yawning. By contrast, the 5-HT1A receptor agonist, 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT, 0.01-0.2 mg/kg) did not significantly influence penile erections or yawning behavior. Experiment 2 evaluated the effects of m-CPP and 8-OH-DPAT on the behavior of male monkeys in the presence of a sexually receptive female monkey which the males could see, hear and smell, but not physically contact. Administration of m-CPP along with presentation of a receptive female stimulated penile erections to a greater extent than they were stimulated by either one of these manipulations alone. Administration of 8-OH-DPAT (0.1 and 0.2 mg/kg) produced a decrease in the percent of monkeys exhibiting penile erections in the presence of the female. In this experiment, yawning was affected in opposite directions, with m-CPP stimulating and 8-OH-DPAT decreasing the frequency of yawning. Experiment 3 assessed the effects of m-CPP on male copulatory behavior of rhesus monkeys. Administration of m-CPP (0.8-3.0 mg/kg) produced a dose-dependent decline in the percent of males initiating copulation and achieving ejaculation.(ABSTRACT TRUNCATED AT 250 WORDS)

8-Hydroxy-2-(di-n-propylamino)tetralin↗

PubMed1995

Nitric oxide is involved in male sexual behavior of rats.

In male rats, whether sexually experienced or sexually naive, the intraperitoneal administration of L-arginine (the natural substrate for nitric oxide synthase) (10, 25, 50 mg/kg) both increased the percentage of copulating in sexually naive rats and improved the indexes of sexual performance in sexually experienced rats, whereas the intraperitoneal administration of N(G)-nitro-L-arginine methyl ester (L-NAME) (a potent inhibitor of nitric oxide synthase) (10, 25, 50 mg/kg) had opposite effects. In contrast, after intracerebroventricular administration, L-arginine (25, 50, 100 microg/rat) had no effect - whether in naive or in experienced rats - whereas L-NAME completely prevented ejaculation in naive rats, at the dose of 100 microg/rat, but had no effect at all in experienced rats, up to the dose of 300 microg/rat. Finally, a direct relationship seems to exist between male copulatory performance and nitric oxide synthase activity in a discrete and defined brain area, the paraventricular nucleus of the hypothalamus: indeed, nitric oxide synthase mRNA expression in this nucleus in sexually potent rats is about twice that in sexually impotent rats. It is concluded that nitric oxide synthase is involved in the expression of male sexual activity, in spite of some inconsistencies that are hard to interpret.

Animals↗

PubMed1991

An atlas of the prenatal mouse brain: gestational day 14.

A prenatal atlas of the mouse brain is presently unavailable and is needed for studies of normal and abnormal development, using techniques including immunocytochemistry and in situ hybridization. This atlas will be especially useful for researchers studying transgenic and mutant mice. This collection of photomicrographs and corresponding drawings of Gestational Day (GD) 14 mouse brain sections is an excerpt from a larger atlas encompassing GD 12-18. In composing this atlas, available published studies on the developing rodent brain were consulted to aid in the detailed labeling of embryonic brain structures. C57Bl/6J mice were mated for 1 h, and the presence of a copulation plug was designated as GD 0. GD 14 embryos were perfused transcardially with 4% paraformaldehyde in 0.1 M phosphate buffer and embedded in paraffin. Serial sections (10 microns thickness) were cut through whole heads in sagittal and horizontal planes. They were stained with hematoxylin and eosin and photographed. Magnifications were 43X and 31X for the horizontal and sagittal sections, respectively. Photographs were traced and line drawings prepared using an Adobe Illustrator on a Macintosh computer.

Animals↗

PubMed1983

Sexual differences in the Japanese quail: behavior, morphology, and intracellular metabolism of testosterone.

Three experiments were carried out to study whether differences in the intracellular metabolism of testosterone (T) can explain sexually differential responses to T in Japanese quail. In the first experiment, a series of dose-response curves in which length of Silastic testosterone implants was related to effects on several behavioral and physiological variables was established. In Experiment 2, adult males and females were assigned to six experimental groups: intact males and females (I-males and I-females), castrated males and females implanted subcutaneously with 40-mm Silastic implants of T (T-males and T-females), and castrated males and females without hormone treatment (CX-males and CX-females). No CX-bird (male or female) and no I-female exhibited male sexual behavior. However, I-males and T-males regularly copulated during the behavioral tests. No crowing was ever heard in CX-animals and I-females. T-females crowed less than T-males and their crowing sounded weaker than those of males. The cloacal glands of T-females were less developed than those of males. Radioimmunoassay of T and 5 alpha-DHT showed that T-males and T-females have similar plasma levels of androgens. No striking differences were observed in the way testosterone is metabolized by the pituitary gland and central nervous tissues of males and females. By contrast, the production of 5 alpha-dihydrotestosterone (5 alpha-DHT) and 5 alpha-androstane-3 alpha, 17 beta-diol (5 alpha, 3 alpha-diol) was higher in the cloacal glands of males than in those of females. These sex differences were not detected between T-males and T-females. In experiment 3, the cloacal gland of males produced more 5 alpha-reduced metabolites than those of females. The pituitary gland of females also produced more 5 beta-androstane-3 alpha, 17 beta-diol (5 beta, 3 alpha-diol). In syringeal muscles, the production of 5 beta-dihydrotestosterone (5 beta-DHT) and 5 beta, 3 alpha-diol was higher in females compared to males.

Animals↗

PubMed1984

Environmental and endocrine control of reproduction in the song sparrow, Melospiza melodia. I. Temporal organization of the breeding cycle.

Endocrinologic investigations of free-living populations of song sparrows, Melospiza melodia, have revealed temporal patterns of secretion of reproductive hormones that differ from those of other monogamous avian species. Males arrive in the breeding area in March whereas females arrive 1-2 weeks later. In males the periods of territory establishment and attraction of a mate are characterized by high circulating levels of luteinizing hormone (LH) and testosterone (T), whereas testis mass is low, and growth of the cloacal protuberance (CPL) is just beginning. In April, testes and CPL develop rapidly reaching a peak in early May when females are laying eggs, and when most copulations occur. Plasma LH and T decline in early April, but increase for a second time in late April and early May coincident with the egg-laying period. Thereafter, circulating LH and T decline during the parental phase, but not to basal levels. Although there is an increase in LH during the egg-laying period for the second clutch, there is no change in T levels. Testis mass, CPL, plasma LH, and T all decline to basal levels simultaneously in late July and August. The high levels of LH and T in March, followed by a temporary decline and resurgence in April and May, indicate that environmental factors in addition to the well known effects of increasing day length can regulate secretion of these hormones. In females, plasma levels of T and dihydrotestosterone (DHT) are also elevated in March and early April, and decline to low levels as the nesting phase progresses. A further decline, to basal levels, occurs in August during the molt. LH and estradiol (E2) titers in females show two peaks coincident with the egg-laying periods for each clutch. Plasma levels of corticosterone (B) increase during the breeding season in males, but not females. In both sexes B levels are basal during the moult and increase in October after moult is completed. Body mass and fat depot decline in males as the nesting phase progresses, and then increase dramatically after breeding is terminated. As expected, females show two peaks of body mass and fat depot coincident with the two periods of egg laying. The postbreeding increases in body mass and fat depot are much less pronounced in females than in males.

Adipose Tissue↗

PubMed1985

An oviposition-stimulating factor in the male accessory reproductive gland of the locust, Locusta migratoria.

The data derived from mating experiments demonstrate that mating has an accelerating effect on oviposition in the female Locusta migratoria. The effect of mating could be mimicked by injection of extracts of the male accessory reproductive gland. The oviposition-stimulating factor was localized in the opalescent gland of the male accessory gland and was transferred to the female via the spermatophore during copulation. Gel filtration of an extract of the opalescent gland revealed a 13,000 Da protein, which, when injected into virgin female locusts, could stimulate the oviposition rate to that seen in mated females. Extracts of the corpus cardiacum also stimulated oviposition when injected into virgin female locusts. This increase was not observably different from that seen after mating. The relevance of these findings will be discussed.

Animals↗

PubMed1986

The endocrine control of reproduction and molt in male and female emperor (Aptenodytes forsteri) and adelie (Pygoscelis adeliae) penguins. II. Annual changes in plasma levels of thyroxine and triiodothyronine.

Changes in plasma thyroxine (T4) and triiodothyronine (T3) levels were studied during a breeding season and in more detail during the postbreeding molt in male and female emperor (Aptenodytes forsteri) and adelie (Pygoscelis adeliae) penguins under natural conditions in the Antarctic. During the 4-month natural fast that accompanies courtship and incubation in male emperors, plasma T4 and T3 levels were maintained around 11 and 0.6 ng/ml, respectively. In courting, fasting female emperors plasma T4 levels were maintained around 10 ng/ml for more than 1 month; plasma T3 levels were around 0.8 ng/ml but were markedly depressed (0.1 ng/ml) at the time of copulation although they increased again (2.2 ng/ml) at oviposition. During the 5-month period of chick rearing, plasma T3 (males and females) and T4 (females) were maintained at the same levels as during courtship and incubation, but plasma T4 levels in male emperors were slightly lower (7 ng/ml). Similar plasma T4 and T3 levels were observed in breeding adelie penguins. These results do not provide any convincing evidence for thyroid-gonadal interrelations in breeding penguins, but demonstrate their capacity to maintain plasma thyroid hormone levels during very prolonged natural fasts. During the heavy postnuptial molt when the birds were fasting, in both species and sexes, marked but separate peaks in plasma T4 and T3 levels occurred concurrently with the initial growth of the new feathers, and with the subsequent shedding of the old plumage, respectively. Peak plasma T4 levels were observed at the time of the emergence of the new feathers out of the skin, and peak plasma T3 levels were roughly concurrent with the maximum daily body weight loss. This is the first strong evidence that increases in plasma T4 and T3 levels are correlated with different stages of molt in a wild seabird. Increased plasma T4 but not T3 levels at the time of feather papilla eruption suggest that T4 is concerned with feather growth, but is not exclusive of a role of T3. Increased plasma T3 but not T4 levels during the reduction in thermal insulation in molting penguins suggest that this hormone rather than T4 might be active in energy metabolism in penguins.

Animals↗

PubMed1991

Plasma levels of luteinizing hormone and androgens in relation to age and breeding status among cooperatively breeding Australian magpies (Gymnorhina tibicen Latham).

Plasma levels of luteinizing hormone (LH), testosterone (T), and 5 alpha-dihydrotestosterone (DHT) were measured in relation to age and social/breeding status among free-living male Australian magpies. Magpies live in territorial groups of up to 20 individuals and due to a largely age-related dominance hierarchy among males, many individuals are prevented from breeding. Adult plumage is not attained until the fourth year, but males can produce motile sperm in their first year. Plasma levels of LH and T peaked just prior to egg-laying among breeding males, but DHT levels remained steady or declined slightly during the breeding period. Adults (greater than 3.5 years) had significantly higher levels of both LH and androgens than did subadults (less than 3.5 years) during the breeding season. Nonbreeding adults had similar levels to those found among the breeding adults, but breeding subadults had higher levels of both LH and androgens than the nonbreeding subadults. These results are interpreted in terms of the opportunities for each of these classes to obtain copulations and are discussed in relation to age-related hormonal secretion in other species.

Aging↗

PubMed1992

Reproductive endocrinology of macaroni (Eudyptes chrysolophus) and gentoo (Pygoscelis papua) penguins. I. Seasonal changes in plasma levels of gonadal steroids and LH in breeding adults.

Changes in plasma luteinizing hormone (LH), testosterone, oestradiol, and progesterone were measured throughout the breeding and molt cycle in free-living male and female macaroni (Eudyptes chrysolophus) and gentoo (Pygoscelis papua) penguins, at Bird Island, South Georgia (54 degrees S, 38 degrees W). These two species are sympatric but have a markedly different breeding cycle. In macaroni penguins plasma levels of all hormones, except LH in males, were significantly elevated at the time of arrival at the breeding colony. In both species and sexes plasma LH, testosterone (males), and estradiol (females) levels were highest during nest-building and postcopulation, coincident with the period of frequent agonistic interactions in males and egg-formation in females. Elevated testosterone levels occurred in females of both species during the postcopulation period and may be associated behaviourally with both sexes being involved in nest defence. Male birds also had elevated estradiol levels. Following copulation, plasma levels of LH, testosterone, and estradiol decreased to basal levels in both sexes and species and, except for a transient increase in testosterone in male macaroni penguins, remained low through to the end of molt. There was no associated rise in LH or testosterone during premolt and early molt despite a further period of agonistic and social interaction, suggesting that birds were in a photorefractory state at this time. Plasma progesterone showed a pattern of variation different from that of the other hormones. In both species and sexes, plasma levels were elevated between arrival and early chick-rearing and then decreased slowly to low levels during molt.

Animals↗

PubMed1983

The regulation of precopulatory behavior by ovarian hormones in the female Mongolian gerbil.

The hormonal regulation of precopulatory behavior in the female Mongolian gerbil was studied using two groups (N = 6) of sexually experienced females. A novel testing procedure was used which involved females living continuously with test males for several days. The test males showed either full sexual behavior (copulating males, C) or only precopulatory behavior (noncopulating males, NC). Experiment 1 investigated changes during the estrous cycle and following ovariectomy in females. Experiment 2 studied the effects of hormonal treatment of these ovariectomized females with 6 micrograms estradiol benzoate (EB) followed by 0.4 mg progesterone (P) or by 0.04 ml arachis oil. When tested with NC males, females displayed a greater range of precopulatory behavior. The patterns could be classified into three groups according to the manner of response to ovariectomy and hormone treatment. Group I patterns (approach, leave, and olfactory investigation of the male's head) were affected by neither ovariectomy nor EB treatment relative to Day 3 levels (Day 3, day preceding estrus; Day 4, estrus), but they were increased to estrous levels by EB and P. Group II patterns (darting, foot-stomping, and the present and piloerection postures) appeared only during estrus, did not appear after ovariectomy, and reappeared only after sequential EB and P treatment. Group III patterns (investigation of the male's anogenital area, allogrooming, ventral gland marking, and sand-rolling) were reduced relative to both estrus and Day 3 levels by ovariectomy and increased above Day 3 levels by EB alone; EB and P treatment further increased Group III patterns to the level of estrus. It is suggested that female precopulatory behavior patterns differ in their responsiveness to ovarian hormones. Estrogen appears to affect those patterns associated with the earliest stages of estrus (Group III).

Animals↗

PubMed1984

Sexual behavior of an androgenized female rhesus macaque with a surgically constructed vagina.

A 17-year-old, prenatally androgenized (ovariectomized) female rhesus macaque was studied. She had achieved penile intromission and ejaculated when treated with testosterone propionate and paired with a receptive female. To test the extent of behavioral defeminization, a vagina was created through surgical intervention and daily injections of 20 micrograms of estradiol benzoate were given. When she was paired with a male on Day 28 of treatment, she proved receptive to his invitations to copulate and the male achieved intromission. The results indicate that prenatal testosterone may morphologically and behaviorally masculinize the genetic rhesus female without eliminating the capacity to respond as a female under appropriate hormonal and environmental stimulation.

Animals↗

PubMed1986

Induction of sexual receptivity in the female broad-headed skink, Eumeces laticeps, by estradiol-17 beta.

Sexual receptivity in the female scincid lizard Eumeces laticeps occurs naturally only during the spring breeding season, which is also when maximal follicular development occurs. The presumption that high estrogen levels are coincidentally present and the need for a reliable method of inducing sexual receptivity for behavioral studies prompted tests of the hypothesis that estrogen induces sexual behavior. A series of experiments established that estradiol-17 beta induces sexual behavior. A series of experiments established that estradiol-17 beta induces sexual receptivity within 4 days when injected every other day at 2.0 micrograms in 20 microliters peanut oil in intact or ovariectomized females. In behavioral tests conducted during August, all control females (intact or ovariectomized injected with vehicle only) rejected courtship whereas all females receiving estrogen copulated. Estrogen injections also induced a statistically significant change from rejection to receptivity within individuals. Initial attempts to implant estradiol-17 beta in Silastic tubes killed all females so treated.

Animals↗

PubMed1987

Testosterone, testis size, seasonality, and behavior in group-living stumptail macaques (Macaca arctoides).

During a 28-month period, data were collected on physiological parameters and sociosexual behavior of 13 adult male members of a large mixed-sex group of stumptail macaques living in an outdoor cage. Monthly measurements of plasma testosterone, testis size, and body weight revealed no systematic seasonality. Seasonal variations did occur in branch shaking and grooming (both with low rates in winter), but not in other behaviors studied (copulation, masturbation, aggression). Dominance ranks were stable throughout the study period and were not significantly correlated with mean testosterone levels. Temporal fluctuations in behavioral frequencies did not parallel testosterone fluctuations. Interindividual differences in behavioral frequencies were often correlated with dominance rank, but not with testosterone levels.

Aggression↗

PubMed1988

The effects of an aromatization inhibitor on the reproductive behavior of male zebra finches.

Recent evidence indicates that aromatizable androgens are more effective than nonaromatizable androgens in restoring normal levels of sexual behavior in castrated male zebra finches (Poephila guttata). To determine whether the efficacy of treatment with aromatizable androgens, is in part due to their conversion to estrogens, castrated male finches were treated with androstenedione (AE), an aromatizable androgen, and their sexual and aggressive behavior was compared with that of castrates treated with AE plus 1,4,6-androstatriene-3,17-dione (ATD), an aromatization inhibitor. Males treated with AE + ATD showed less courtship activity and less copulatory behavior than AE-treated males, and were unlikely to have nests. Estradiol (E), when given concurrently with AE + ATD, reversed the inhibitory effects of ATD and restored levels of courtship and copulation to those observed in AE-treated males. Only AE- and AE + ATD + E-treated males displayed aggressive behaviors, but the frequency of such behaviors was so low that there were no significant differences across groups. These data affirm the importance of estrogen in the control of reproductive activities in male zebra finches and indicate that aromatization may be an obligatory step for maintaining normal levels of sexual and aggressive behavior.

Aggression↗

PubMed1992

The abnormal conduct of capercaillies Tetrao urogallus.

The frequency, behavior, and testosterone levels of deviant capercaillies were studied in southern Finland. Roughly 1% of the population was estimated to behave abnormally. Deviant males display and show threatening behavior toward not only humans, but also attacked stuffed capercaillie males and without hesitation copulated with a stuffed female. Deviant females appear tame and crouch in front of humans, but avoid males. The testosterone level in deviant males was about five times higher than that of normal displaying males. The origin of this striking phenomenon is still unclear, although it must be connected with display. Two, though not mutually exclusive, proximate mechanisms for the development of this abnormal behavior are presented: anomalous sex hormone concentrations and incorrect sexual imprinting. The ultimate reason for the apparent increase in numbers of deviant capercaillies is probably logging which diminishes populations and, thereby, favors the spreading of abnormal behavior.

Aggression↗

PubMed1989

Observations on egg production by Toxocara pteropodis.

Studies in juvenile Pteropus poliocephalus showed an average daily egg production by Toxocara pteropodis of 25,000 per female, with concentrations of up to 16,000 epg. regardless of whether eggs were fertile or infertile. Production commenced as early as 35 and as late as 48 days post-partum and rose to plateau average levels over about 10 days. For 23 days one bat passed infertile eggs which, over 2 days, were then replaced completely by fertile eggs. The implicit delay in maturation of a male nematode suggests that transmammary passage of larvae to suckling bats may persist for at least 3 weeks. Patency was terminated by the spontaneous expulsion of worms. If male worms were lost first, the egg output converted from fertile to 100% infertile within 48 h and the females were devoid of spermatozoa, suggesting that T. pteropodis copulate at least once daily. In prolonged infections, worm fecundity and egg fertility diminished, so that females with stored spermatozoa were producing mixtures of fertile and infertile eggs.

Animals↗

PubMed1975

Studies on chemically induced dominant lethality. I. The cytogenetic basis of MMS-induced dominant lethality in post-meiotic male germ cells.

Young adult male mice were injected intravenously with doses of methyl methanesulfonate(MMS) ranging from 25 to 100 mg/kg body weight. These males were serially mated to superovulated females from day 1 post injection to day 23 post injection. The morning after mating (about 4-6 h post-copulation) the females were sacrificed and ova flushed from the ampulla. The ova were cultured, in the presence of colchicine, for 26 h and metaphase preparations made of the first cleavage division. Chromosome analysis was done and the types, and extent, of chromosome aberrations correlated to previously published dominant lethal data at the same MMS doses and time intervals. The types of aberrations seen were predominantly double fragments (presumably isochromatid deletions), chromatid interchanges, and some chromatid deletions, as well as shattering effect on the male complement at the highest dose and the time of peak sensitivity to dominant lethal induction. When the frequency of cells containing a cytologically visible aberration is compared to the total dominant lethal data an excellent correlation is obtained. Furthermore, the frequency of highly damaged cells, agrees very well with estimated frequencies of preimplantation loss. These data strongly suggest that chromosome aberrations seen at the first cleavage stage are the basis of MMS-induced dominant lethality.

Animals↗