A Drosophila male pheromone affects female sexual receptivity

Sex pheromones are chemical signals frequently required for mate choice, but their reciprocal role on mate preference has rarely been shown in both sexes. In Drosophila melanogaster flies, the predominant cuticular hydrocarbons (CHs) are sexually dimorphic: only females produce 7,11-dienes, whereas 7-tricosene (7-T) is the principal male CH. Males generally prefer females with 7,11-dienes, but the role of 7-T on female behaviour remains unclear. With perfumed males, control females mated faster and more often with males carrying increased levels of 7-T showing that this CH acts as a chemical stimulant for D. melanogaster females. Control females-but not antenna-less females-could detect small variation of 7-T. Finally, our finding that desat1 mutant female showed altered response towards 7-T provides an additional role for this gene which affects the production and the perception of pheromones involved in mate choice, in both sexes.     

A recombinant courtship pheromone affects sexual receptivity in a plethodontid salamander

Pheromones are important chemical signals for many vertebrates, particularly during reproductive interactions. In the terrestrial salamander Plethodon shermani, a male delivers proteinaceous pheromones to the female as part of their ritualistic courtship behavior. These pheromones increase the female's receptivity to mating, as shown by a reduction in courtship duration. One pheromone component in particular is plethodontid receptivity factor (PRF), a 22-kDa protein with multiple isoforms. This protein alone can act as a courtship pheromone that causes the female to be more receptive. We used a bacterial expression system to synthesize a single recombinant isoform of PRF. The recombinant protein was identical to the native PRF, based on mass spectrometry, circular dichroism spectra, and a behavioral bioassay that tested the effects of recombinant PRF (rPRF) on female receptivity (21% reduction in courtship duration). The rPRF appears to mimic the activity of a mixture of PRF isoforms, as well as a mixture of multiple different proteins that comprise the male courtship gland extract. Pheromones that are peptides have been characterized for some vertebrates; to date, however, rPRF is one of only 2 synthesized vertebrate proteins to retain full biological activity.     

Diurnal variation of heat intake in ovariectomized, steroid-treated rats

Ovariectomized rats trained to work for radiant heat reward in a cold environment were implanted with subcutaneous Silastic capsules containing either estradiol, progesterone, both estradiol and progesterone, or no hormone. The hormone treatments produced an average plasma estradiol concentration of 41 pg/ml and progesterone concentration of 20–50 ng/ml. All groups obtained more heat behaviorally when tested during the light phase of the LD cycle than when tested in the dark. Body temperatures and metabolic rates were higher during the night than during the day. There were no differences between groups in behavioral heat intake or body temperature. All hormone-treated groups showed a greater reduction in core temperature than the control group when an exogenous source of heat was not available, but there was no substantial effect of the hormone treatments on metabolic rate except for a 6–7% increase in metabolism of the estrogen group. The increased cooling rate of all hormone-treated groups may indicate a nonspecific steroid-induced increase in heat loss in the cold. The diurnal variation in heat intake establishes the LD cycle as a significant variable in thermoregulatory behavior of the rat. Thus, behavioral heat intake is high during the day when metabolism and body temperature are low, and low at night when metabolism and body temperature are high in this nocturnal species.     

Dexamethasone suppression of sexual behavior in the ovariectomized mare

The influence of steroids of adrenal cortical origin on estrous behavior in the ovariectomized mare was evaluated by adrenal suppression via dexamethasone (DEX) administration in two experiments. In Experiment I, 12 mares (six DEX, six control) were tested for sexual behavior in harem groups (two DEX and two control mares plus one stallion per group) for 9 consecutive days. In Experiment II, estradiol (E₂) was given to a group of DEX-treated mares as an additional control. Twelve mares (four DEX, four DEX + E₂, and four control) were tested in harem groups (one DEX, one DEX + E₂, and one control mare plus one stallion per group) for 10 days. All DEX mares showed a clear suppression of sexual response compared to control or DEX + E₂ mares, indicating that the estrous behavior seen in ovariectomized mares may be due to steroids from the adrenal cortex. The control and DEX + E₂ mares were similar in all measures of proceptivity. Despite being more receptive, as indicated by fewer negative responses, the DEX + E₂ mares received fewer intromissions and ejaculations than did the control animals. The ability of estradiol to induce estrous behavior in the dexamethasone-suppressed mare notwithstanding, other adrenal steroids, e.g., androgens, may be involved in estrous behavior in the untreated, ovariectomized mare.     

The phytoestrogen ferutinin improves sexual behavior in ovariectomized rats

The present study was designed to examine the effect of ferutinin chronic administration on sexual behavior of ovariectomized non-estrogen-primed rats. Starting from 3 weeks after ovariectomy, female rats were orally treated with ferutinin at the doses of 0.2 and 0.5 mg/kg, daily for 4 weeks. Ferutinin's effect was compared with that of estradiol benzoate, subcutaneously injected at the dose of 1.5 μg/rat twice a week. Animals were tested for sexual motivation, receptivity and proceptivity after 1, 2 and 3 weeks of treatment and for paced mating behavior after 4 weeks of treatment. Before each experimental test, they received progesterone injection (500 μg/rat).Both dosages of ferutinin significantly increased the receptive behavior in a time-dependent manner, as well as estradiol benzoate did. Also proceptive behaviors increased in ferutinin-treated animals in comparison with control ones. During the partner preference test ferutinin was able to induce a significant preference for a sexually active male over a sexually receptive female. Moreover, ferutinin restored a normal paced mating behavior, which had been suppressed by ovariectomy. These results show that ferutinin exerts an estrogenic activity in ovariectomized non-estrogen-primed female rats.     

Effect of 5 alpha-dihydrotestosterone on sexual receptivity and neural progestin receptors in ovariectomized rats given pulsed estradiol

Experiments were carried out to examine the mechanism whereby 5 alpha-dihydrotestosterone (DHT) antagonizes the stimulatory effects of estrogen plus progesterone (P) on sexual receptivity (lordosis) in the ovariectomized rat. Estradiol (E2; 1 microgram s.c. in 10% ethanol) was administered in a discontinuous (pulsed) treatment regimen thought to mimic phase requirements of estrogen action; two injections of E2 were given either 6 or 12 h apart (first injection, Hour 0). Progesterone (0.5 mg in oil) was injected at Hour 20, and behavioral testing occurred at Hour 24. Dihydrotestosterone (2.5 mg s.c. in 10% ethanol/propylene glycol) inhibited lordosis when it was given before (-12 or -3 h), between (+3, or -3 and +3 h), or after (+8 h) the two E2 injections, but was not effective when given at +20 h. Significant inhibition of E2 + P-induced lordosis was achieved by 2.5 but not 1.0 or 0.2 mg DHT at -3 h, while uterine weights in the same animals were reduced significantly by 2.5 and 1.0 mg DHT. Serum E2 and DHT concentrations peaked rapidly after injection, declining to near baseline by 3 and 12 h, respectively. Induction of cytosolic progestin receptors (cPR) in the preoptic area and medial basal hypothalamus by estrogen was not prevented by DHT when animals were given the two pulsed E2 injections or daily injections of estradiol benzoate, although P was able to override the inhibitory behavioral effects of DHT in the latter but not the former group.(ABSTRACT TRUNCATED AT 250 WORDS)     

Mating-induced loss of sex pheromone and sexual receptivity in insects with emphasis on Helicoverpa zea and Lymantria dispar

Mating in most species of insects leads to a transient or permanent loss in sexual receptivity of the females. Among moths, this loss of receptivity is often accompanied with a loss of the sex pheromone in the absence of calling, which also could be temporary or permanent. Most of the earlier work on changes in reproductive behavior after mating was done with Diptera in which sperm and/or male accessory gland secretions were shown to be responsible for termination of receptivity. In the corn earworm moth, Helicoverpa zea, mated females become depleted of pheromone and become nonreceptive to further mating attempts, but only for the remainder of the night of mating. A pheromonostatic peptide isolated from the accessory glands of males may be responsible for the depletion of pheromone, while the termination of receptivity is independently controlled. In the gypsy moth, Lymantria dispar, the changes in behavior following mating are permanent. In this species, the switch from virgin to mated behavior involves three steps: a physical stimulation associated with mating, transfer of viable sperm to the spermatheca, and commencement of oviposition. Signals generated by these factors operate through neural pathways and, unlike in H. zea, accessory gland factors seem not to be involved. © 1994 Wiley-Liss, Inc.

1 This article is a US Government work and, as such, is in the public domain in the United States of America.

     

Conspecific and heterospecific pheromone effects on female receptivity

Courtship pheromones play an important role in salamander reproductive behaviour. In salamanders of the family Plethodontidae, males deliver specialized pheromones to females during courtship interactions. These courtship pheromones increase female receptivity and may be involved in mate discrimination. In order to test hypotheses related to mate discrimination, we staged courtship encounters between male-female Plethodon shermani pairs in which the female received pheromones obtained from either conspecific (P. shermani) or heterospecific (P. yonahlossee orP. montanus ) males. Both conspecific and heterospecific pheromones increased female receptivity. Moreover, pheromones from both heterospecific species were as effective as the conspecific pheromone in increasing female receptivity inP. shermani females. Our results suggest that the courtship pheromone signal and function may be conserved across related species, with mate discrimination occurring before pheromone delivery. Copyright 2003 The Association for the Study of Animal Behaviour. Published by Elsevier Ltd. All rights reserved.     

Tissue spaces during development and regression of the decidual cell reaction in ovariectomized, steroid-treated mice

Changes in the extracellular and blood spaces of the uterus were assessed from the distribution volumes of 51Cr-EDTA and 51Cr-labelled red blood cells during the development and regression of the artificially induced decidual cell reaction in ovariectomized, steroid-treated mice. The normally high values for uterine extracellular space (0.35-0.40 microliter/mg) fell to less than 0.20 microliter/mg in association with decidual growth. Uterine blood space increased from around 0.02 microliter/mg to 0.03-0.05 microliter/mg with decidual development. Induction of decidual regression by removal of s.c. progesterone implants caused a rapid decline in tissue blood volume to reach control values (0.01-0.02 microliter/mg) within 24 h and preceded any reduction in uterine weight. Uterine vascular permeability, as determined from the tissue accumulation of 125I-labelled human serum albumin, fell with a similar time course. Tissue extracellular space returned to the higher control values within 48 h of initiating decidual regression.     

Induction of sexual behavior in ovariectomized rhesus females with 19-hydroxytestosterone

Eight sexually experienced long-term ovariectomized female rhesus monkeys were given tests of sexual behavior following treatment with 19-hydroxytestosterone (19-OH-T, 1 mg/day for 13 days), and their performance was compared with that following treatment with estradiol benzoate (EB, 10 μg/day for 13 days). Each female was tested for 10 min with each of nine adult males. Blood samples were taken on the last day of treatment with EB, at the end of the intervening 3-month period of no treatment, and on the last day of treatment with 19-OH-T. Blood levels of testosterone and estradiol were quantified by radioimmunoassay. Mean rate of presenting at a distance (proceptive behavior) was significantly higher (P < 0.05) when they were treated with 19-OH-T, but the ratio of presents to male contacts (receptive behavior) was significantly higher (P <0.05) when they were treated with EB. All other components of female sexual behavior were the same. Males displayed fewer annoyance responses (rejecting jerk, P < 0.05) when the females were treated with 19-OH-T than when they were treated with EB. All other male responses occurred with the same frequencies under the two female treatment conditions. Injection of 19-OH-T and EB both resulted in plasma testosterone and estradiol levels higher than those found in the untreated condition. Testosterone levels did not differ under the two treatments (P > 0.05), but estradiol levels were higher under EB treatment than under 19-OH-T (P < 0.05). This study suggests that both testosterone and estradiol are essential for maximum sexual performance and that various components of sexual behavior may be differentially influenced by the ratio of testosterone to estradiol in plasma.     

Sensitization of sexual behavior in ovariectomized rats by chronic estradiol treatment

The ovariectomized (OVX) rat treated with estradiol benzoate (EB) is used to elucidate neuroendocrine mechanisms of sexual behavior. Chronic behavioral and pharmacological manipulations can be confounded by rising baselines, since females are behaviorally more sensitive to repeated EB injections. The literature lacks a systematic examination of chronic effects of EB administered alone to the sexually experienced OVX rat. Long–Evans rats were repeatedly treated (8 tests) with s.c. injections of 2, 5, or 10 μg EB at different time intervals (4 or 8 days). Female sexual behaviors as well as receipt of mounts, intromissions and ejaculations from the male were observed in the unilevel 4-hole pacing chamber. The effects of adrenalectomy (ADX) and strain (Long–Evans vs. Wistar) were also assessed. Long–Evans OVX rats treated with 5 μg EB every 8 days showed persistently low levels of sexual behavior. Sensitization was most robust following 10 μg EB at 4-day intervals. Very few sexual behaviors were ever induced by 2 μg EB. ADX did not affect the development of behavioral sensitization by 10 μg EB. Therefore, to achieve a low steady state of sexual behaviors in sexually experienced Long-Evans OVX rats 5 μg of EB administered every 8 days is optimal, whereas a persistently high level of sexual behaviors is induced with 10 μg EB administered every 4 days. OVX Wistar rats are behaviorally more sensitive to EB. Behavioral sensitization to EB may serve as a mechanism to optimize reproductive success.     

Cyclic estradiol treatment normalizes body weight and restores physiological patterns of spontaneous feeding and sexual receptivity in ovariectomized rats

Hypothalamic-pituitary-gonadal axis function strongly influences feeding and body weight in cycling females in many species. To test the sufficiency of cyclic variations in plasma estradiol to reproduce normal patterns of spontaneous feeding, food intake, and body weight, ovariectomized Long-Evans rats were subcutaneously injected every fourth day with 2 microg estradiol benzoate or with the oil vehicle alone. Cyclic estradiol treatment completely normalized the trajectory of body weight gain and total food intake through seven treatment cycles. The hyperphagia of ovariectomized rats was expressed as an increase in spontaneous meal size. Meal frequency decreased, but not enough to compensate for the increase in meal size. Estradiol treatment normalized both parameters. In addition, cyclic estradiol treatment produced a further phasic decrease in meal size (and increase in meal frequency) and a decrease in food intake during the second night after injection. This phasic change is similar to the feeding changes occurring during estrus in intact rats. Sexual receptivity was measured during the eighth estradiol treatment cycle, 4 h after injection of 0.5 mg progesterone. Lordosis scores at the time of the treatment cycle modeling estrus were maximal, and scores at the time modeling diestrus were slightly increased over those of rats that did not receive estradiol. Finally, plasma estradiol levels, measured during the ninth treatment cycle, revealed a near-normal cyclic pattern of plasma estradiol levels. These results provide the first demonstration that the induction of a cyclic, near-physiological pattern of plasma estradiol is sufficient to maintain normal levels of body weight, spontaneous feeding patterns, total food intake, and (together with progesterone) sexual receptivity in ovariectomized rats.     

Sensitivity of female rabbits to changes in photoperiod as measured by pheromone emission

Newborn rabbits are completely dependent on a pheromone on the mother's belly for the release of nipple-search behaviour and suckling. Using the stereotyped behavioural response of the pups as a bioassay it could be shown that: 1. In non-breeding does pheromone emission is stimulated by experimental long day and suppressed by experimental short day conditions within 1 to 2 weeks of reversing the light regime. 2. Under constant long day conditions pheromone emission, readiness to mate, conception rate and litter size remain high with no evidence of endogenous seasonal rhythmicity. 3. Experimental changes in daylength of just 1 or 2 h in either direction are sufficient to induce marked alterations in the level of pheromone emission, number of successful matings and average litter size within 2 to 3 weeks. Pheromone emission would thus seem to provide a sensitive test of photoperiodic responsiveness in non-breeding female rabbits, and a convenient, non-invasive indicator of their reproductive state.     

Influence of short-term relocation and male exposure on sexual receptivity and reproduction in artificially inseminated lactating doe rabbits

A study was conducted to evaluate the effect of short-term relocation and male exposure on receptivity rate, kindling rate and total born per litter in lactating does under an artificial insemination (AI) programme. Thirty-two, 2-month-old New Zealand White rabbits were randomly allocated to one of four treatments: (1) relocation and male exposure; (2) relocation without male exposure; (3) no relocation with male exposure; (4) no relocation without male exposure (control). Relocation and male exposure were done 8-10 h before the time of service. First insemination was when does reached 3200 g body weight and does were bred 4-13 days after parturition across parities during a 6 month reproduction period. Of all breeding records, 125 inseminations and 91 kindlings were from nursing does. The mean interval from parturition to insemination for nursing does was 10.3 days. Relocation of lactating does resulted in greater (P<0.01) receptivity rate at service (74.8%) as compared with no relocation (55%). Receptivity rate was not influenced by male exposure. However, the interaction of relocationxmale exposure tended to be significant (P=0.07). Receptivity rate in relocated does exposed to males was 62.8 and 86.7% without exposure while in non-relocated does male exposure showed no effect. Kindling rate was not influenced by relocation or male exposure. The mean total born per litter in relocated and non-relocated does was 8.05 +/- 0.33 and 7.39 +/- 0.36, respectively, but no significant difference was observed. There was no effect of male exposure on total born per litter (7.85 +/- 0.34 versus 7.59 +/- 0.34 without male exposure). However, interaction of relocationxmale exposure on this variable was significant (P=0.009). Male exposure in relocated does decreased the size of the litter (7.52 +/- 0.46 versus 8.58 +/- 0.47 without male exposure) whereas mean values in non-relocated does increased when they were exposed to males (8.18 +/- 0.52 versus 6.60 +/- 0.49). Short-term relocation improved receptivity rate and reproduction in lactating does under an artificial insemination programme. Preliminary results indicated that male exposure in non-relocated does improves the total born per litter at a similar level than relocated does without male exposure. Relocation combined with male exposure decreased receptivity rate and total born per litter as compared with relocated does without male exposure, but the reproductive performance in the former was greater as compared with those does where no relocation occurred without male exposure.     

Persistence of sexual behavior in ovariectomized stumptail macaques following dexamethasone treatment or adrenalectomy

Daily administration over a period of 6 weeks of increasing doses of dexamethasone sodium phosphate (DEX) to seven long-term ovariectomized female stumptail monkeys significantly lowered circulating levels of testosterone without reducing any aspect of the females' sexual behavior or that of their male partners. Since treatment with DEX failed to suppress serum testosterone levels completely an additional experiment was performed in which the sexual behavior of five ovariectomized stumptails was compared before and after bilateral adrenalectomy, combined with chronic administration of both gluco- and mineralocorticoids. Serum levels of both testosterone and estradiol were reduced to very low levels in females after ovariectomy and adrenalectomy, yet no significant depression of females' sexual performance or that of their male partners occurred. Subsequent sc administration of estradiol or estradiol + testosterone in Silastic capsules to ovariectomized, adrenalectomized stumptails had little effect on sexual interaction. In a third experiment five ovariectomized stumptails which initially were relatively unreceptive and unattractive to males were given first testosterone and then testosterone + estradiol sc in Silastic capsules. One of the three indexes of females' receptivity increased significantly after testosterone; however, no other essential aspect of sexual interaction was affected. These findings suggest that sex steroids are normally not required in the female stumptail macaque for activation of preceptive and receptive sexual behaviors or for maintenance of sexual attractivity.     

Androgen dependence of a marking pheromone in rat urine

The voided urine of intact male rats has an avoidance effect on the normal adult male. This quality is not present in bladder urine of adult males, nor in voided urine of castrated or immature males. The avoided substance can be extracted with ethyl ether from normal male voided urine. It is suggested that the marking pheromone is produced by an androgen controlled gland(s) and released into the urine during urination.     

Renewal of sexual receptivity in mated female mosquitoes, Aedes aegypti

ABSTRACT. Females of Aedes aegypti (L.) (Diptera, Culicidae) were not receptive to mating 1 h after the initial insemination or at later times throughout the first gonotrophic cycle. A significant proportion of these females (75–90%) were inseminated again prior to the second gonotrophic cycle. Insemination was determined by the detection in females of sperm labelled with ³ H(G)-adenine or ³²PO₄ after matings with radiolabeled males. Females deprived of males after the first insemination displayed an abnormal reduction in fertility throughout successive gonotrophic cycles.