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PubMed1990

Changes in ingestive behaviors and body weight following intracranial application of 17 alpha-estradiol.

The present experiment was conducted to determine if central implants of 17 alpha-estradiol could influence food intake, water intake, and body weight in ovariectomized rats. A total of fifteen animals were fitted with bilateral guide cannulae in the paraventricular nucleus (PVN) and stimulated unilaterally with cholesterol and 17 alpha-estradiol in each side of the brain. Compared with cholesterol treatment, 17 alpha-estradiol implants in the PVN significantly lowered food intake and body weight but did not affect water intake. These findings indicate that the PVN is a brain region responsive to the effects of 17 alpha-estradiol on feeding behavior, and support the hypothesis that the effects of estrogens on ingestive and reproductive behaviors are organized separately within the brain.

Animals↗
PubMed1992

LiCl aversive conditioning has transitory effects on pheromonal responsiveness in male house mice (Mus domesticus).

Appetitive and aversive experiences influence whether odors elicit precopulatory behavior from male rodents. A role for aversive experience in odor-elicited reproductive behaviors had been demonstrated for hamsters and rats, but similar work on house mice had not been performed. Four experiments examined whether lithium chloride (LiCl) aversive conditioning would alter two precopulatory behaviors (ultrasonic vocalizations and olfactory preference) that male house mice normally exhibit to female urine. Lithium chloride was used to aversively condition male house mice to either female urine odor, female urine in drinking water, the female herself, or a novel odor. Independent tests of taste aversion establishment were also conducted. In these experiments, LiCl aversive conditioning produced robust taste aversions to water adulterated with either female urine or a novel odorant/tastant (isoamylacetate), but only transitory decrements in odor-elicited, male-typical precopulatory behaviors. We conclude that aversive conditioning is unlikely to be a significant factor affecting male mouse precopulatory behavior.

Animals↗
PubMed2001

Pubertal and seasonal plasticity in the amygdala.

The present experiments investigated the effects of pubertal maturation and photoperiod on the size of brain regions that mediate mating behavior in the male Syrian hamster. We hypothesized that the low levels of reproductive behavior exhibited by prepubertal and photoinhibited males would be correlated with morphological changes in the neural circuit that mediates mating behavior. We found that the Nissl-stained cross-sectional area of the posterodorsal subdivision of the medial amygdala was significantly smaller in prepubertal and photoinhibited males compared to photostimulated adult males. These differences appear to be caused by a decrease in somal size of individual cells in the ventral aspect of this nucleus. We also found that prepubertal males have a larger anterior subdivision of the medial amygdala (MeA) compared to adults. This difference in the MeA does not appear to be caused by alteration in somal size since somal size did not differ significantly between juveniles and adults. It is concluded that the neural circuit that mediates male mating behavior in this species is capable of significant morphological plasticity during both pubertal development and in adulthood. Furthermore, these alterations may reflect underlying mechanisms of the deficits in sexual behavior exhibited by prepubertal and photoinhibited males.

Amygdala↗
PubMed2000

Anticipation of oxidative damage decelerates aging in virgin female medflies: hypothesis tested by statistical modeling.

Empirical analysis of survival data obtained from large samples of Mediterranean fruit flies shows that the trajectory of the mortality rate for virgin females departs from that for females maintained in mixed sex cages. It increases, decelerates, reaches its maximum, declines and then increases again within the reproductive interval. Non-virgin females, however, display an early-age plateau instead of this dip. We assume that these deviations are produced by the interplay between changes in oxygen consumption associated with reproductive behavior and the antioxidant defense that acts against anticipated oxidative damage caused by reproduction. Since there are no data on antioxidant mechanisms in medflies available that explain the observed patterns of mortality, we develop a model of physiological aging based on oxidative stress theory, which describes age-related changes in oxygen consumption and in antioxidative capacity during the reproductive period. Using this model, we simulate virtual populations of 25,000 virgin and non-virgin flies, calculate the respective mortality rates and show that they practically coincide with those of experimental populations. We show that the hypothesis about the biological support of reproduction used in our model does not contradict experimental data. The model explains how the early-age dip and plateau might arise in the mortality rates of female medflies and why the male mortality pattern does not exhibit such deviations.

Aging↗
PubMed2002

Obesity-inducing amygdala lesions: examination of anterograde degeneration and retrograde transport.

Small lesions centered in the posterodorsal region of the medial amygdala resulted in excessive weight gains in female rats. Unilateral lesions were nearly as effective as bilateral lesions in the first 48 h after surgery (+21 to +32 g). Assessment of lesion damage was done by both qualitative evaluation and by a quantitative grid-point counting method. The critical sites for weight gain were the intra-amygdaloid bed nucleus of the stria terminalis and the posterodorsal medial amygdaloid nucleus. Incidental damage to the overlying globus pallidus was negatively related to weight gain. The cupric silver method for demonstrating axonal degeneration was applied to brains with obesity-inducing lesions. A dense pattern of degenerating terminals was found in the lateral septum, amygdala, ventral striatum, and ventromedial hypothalamus. Degeneration in the paraventricular nucleus of the hypothalamus was scarce or absent. Small retrograde tracer injections made in either the intra-amygdaloid bed nucleus of the stria terminalis or in the posterodorsal medial amygdaloid nucleus labeled cells in the amygdala, lateral septum, and hypothalamus, reciprocating the anterograde projections from the amygdala to these areas. The data suggest that subdivisions of the posterodorsal amygdala participate in the regulation of feeding in a manner that is similar to the better-known role of this part of the brain in mediating reproductive behavior. Although topographical differences may exist within the amygdaloid and hypothalamic subdivisions regulating these two sexually dimorphic behaviors, the relays engaged by feeding-related connections and those related to reproduction are remarkably parallel.

Amygdala↗
PubMed1997

A cellular approach to the study of complex natural behavior patterns in the ragged sea hare (Bursatella leachii), a marine invertebrate indigenous to Puerto Rico.

The ragged sea hare (Bursatella leachii), an aplysiid mollusc indigenous to the tropical waters of Puerto Rico, possesses numerous properties that make it suitable for a neuroethological approach to the study of complex behavior patterns. Field studies spanning three years have established a location and season of Bursatella availability on the north coast of the island. In the natural habitat, the Bursatella exhibit a daily rhythm of behavior patterns in which feeding-related activities predominate during the day and reproductive behaviors predominate at night. Some aspects of this natural pattern persist in animals held in the laboratory. The Bursatella nervous system contains large neurons, some of which appear to be homologous to cells that have been characterized extensively in related species. Following isolation of the nervous system, neural centers associated with feeding movements and locomotion retain extraordinarily robust rhythm generating capabilities. It is proposed that this species offers unique opportunities for deriving general principles governing the regulation and integration of central pattern generator circuits underlying complex natural behavior patterns.

Animals↗
PubMed2005

Coordinated and dissociated effects of testosterone on singing behavior and song control nuclei in canaries (Serinus canaria).

Temperate zone songbirds that breed seasonally exhibit pronounced differences in reproductive behaviors including song inside and outside the breeding season. Springlike long daylengths are associated with increases in plasma testosterone (T) concentrations, as well as with increases in singing and in the volume of several brain nuclei known to control this behavior. The mechanisms whereby T can induce changes in behavior and brain, and whether or not these effects are differentially regulated, have recently begun to be examined, as has the question of the relative contributions of T and its androgenic and estrogenic metabolites to the regulation of this seasonal behavioral and neural plasticity. In this experiment, we examined the effects of T, 5alpha-dihydrotestosterone, or 17beta-estradiol treatment on castrated male canaries housed on short days and compared neural and behavioral effects in these males to similarly-housed males given only blank implants. We observed that only T treatment was effective in eliciting significant increases in singing behavior after 11 days of hormone exposure. In addition, T alone was effective in increasing the volume of a key song production nucleus, HVC. However, at this time, none of the steroids had any effects on the volumes of two other song control nuclei, Area X of the medial striatum and the robust nucleus of the arcopallium (RA), that are efferent targets of HVC, known to be regulated by androgen in canaries and also to play a role in the control of adult song. T can thus enhance singing well before concomitant androgen-induced changes in the song control system are complete.

Androgens↗
PubMed1997

Tokens of love: functions and regulation of Drosophila male accessory gland products.

A male fruit fly influences the behavior and physiology of his mate via molecules that he transmits to her in his semen. The mated female fly has an elevated rate of egg laying, a decreased receptivity to mating and a shorter life span; she also stores sperm from the mating. Molecular genetic analyses possible in this insect model system permit the dissection of seminal fluid components that cause these mating responses in the female. Studies with transgenic and mutant flies have shown that products of the male's accessory gland cause short-term changes in the female's behavior and physiology; persistence of these changes requires the storage of sperm. Further dissection of accessory gland function has defined several molecules that cause these effects. A "sex peptide" and a prohormone-like molecule (Accessory gland protein 26Aa) stimulate the female's egg-laying rate; the sex peptide also depresses her receptivity to mating. A large glycoprotein (Acp36DE) appears to function in "corralling" sperm for storage. Studies of accessory gland products and the regulation of the genes that encode them will be important in understanding insect reproduction, behavior, and speciation and ultimately in designing ways to control the impressive fertility of unwanted insects. These studies also provide excellent models to address basic questions in cell biology such as the control of genes in response to sex-specific, mating-regulated and cell type-specific cues and the function and targeting of peptide hormones.

Animals↗
PubMed2002

The role of delta-opioid receptors in estrogen facilitation of lordosis behavior.

The present study investigated the role of delta-opioid receptors (ORs) in estrogen facilitation of female rat reproductive behavior (lordosis). Infusion of 2 microg of the selective delta-OR agonist [D-Pen(2),D-Pen(5)]-enkephalin (DPDPE), into the third ventricle facilitated lordosis behavior in ovariectomized (OVX) rats injected with estrogen (E) 48 and 24 h before behavioral testing. Pretreatment with the selective delta-OR antagonist naltrindole (NTDL) blocked DPDPE effects on lordosis behavior. Ventricular infusion of NTDL (40 microg) also suppressed lordosis behavior in fully receptive OVX rats primed with both E and progesterone (P). In addition, NTDL blocked lordosis behavior when infused into the ventromedial nucleus of the hypothalamus (VMH) but not into the medial preoptic area (mPOA). Site-specific infusion of DPDPE into the VMH had dose-dependent, dual effects on lordosis behavior. While a very low dose of DPDPE (0.01 microg) facilitated lordosis behavior, a higher dose (1.0 microg) inhibited receptivity in OVX rats primed with E and a low dose (50 microg) of P. We used 3H-DPDPE to measure the density of delta-ORs in OVX rats treated with vehicle or with E by receptor autoradiography. E treatment did not have any effect on the density of DPDPE binding sites in the VMH, mPOA, medial amygdala, or caudate putamen. The behavioral effects of the ligands used in this study suggest that activation of delta-OR in the VMH by endogenous opioids facilitates estrogen-dependent lordosis behavior.

Analgesics, Opioid↗
PubMed2005

Phylogenetic perspectives in the evolution of parental care in ray-finned fishes.

Among major vertebrate groups, ray-finned fishes (Actinopterygii) collectively display a nearly unrivaled diversity of parental care activities. This fact, coupled with a growing body of phylogenetic data for Actinopterygii, makes these fishes a logical model system for analyzing the evolutionary histories of alternative parental care modes and associated reproductive behaviors. From an extensive literature review, we constructed a supertree for ray-finned fishes and used its phylogenetic topology to investigate the evolution of several key reproductive states including type of parental care (maternal, paternal, or biparental), internal versus external fertilization, internal versus external gestation, nest construction behavior, and presence versus absence of sexual dichromatism (as an indicator of sexual selection). Using a comparative phylogenetic approach, we critically evaluate several hypotheses regarding evolutionary pathways toward parental care. Results from maximum parsimony reconstructions indicate that all forms of parental care, including paternal, biparental, and maternal (both external and internal to the female reproductive tract) have arisen repeatedly and independently during ray-finned fish evolution. The most common evolutionary transitions were from external fertilization directly to paternal care and from external fertilization to maternal care via the intermediate step of internal fertilization. We also used maximum likelihood phylogenetic methods to test for statistical correlations and contingencies in the evolution of pairs of reproductive traits. Sexual dichromatism and nest construction proved to be positively correlated with the evolution of male parental care in species with external fertilization. Sexual dichromatism was also positively correlated with female-internal fertilization and gestation. No clear indication emerged that female-only care or biparental care were evolutionary outgrowths of male-only care, or that biparental care has been a common evolutionary stepping stone between paternal and maternal care. Results are discussed in the context of prior thought about the evolution of alternative parental care modes in vertebrates.

Animals↗
PubMed2004

Organizational effects of diethylstilbestrol on brain vasotocin and sexual behavior in male quail.

In Japanese quail, we previously described a sexual dimorphism of the parvocellular vasotocin system of the limbic region that, as the reproductive behavior, is steroid-sensitive and is organized during embryonic life by the exposure to estradiol. We verified in this study whether diethylstilbestrol, a chemical xenoestrogen, has analogous organizational effects on the vasotocin system of limbic regions and on copulatory behavior of male Japanese quail. We injected in the yolk sac of 3 day-old quail embryos diethylstilbestrol or estradiol benzoate (a treatment which suppresses male copulatory behavior in adulthood and reduces vasotocin innervation), or sesame oil (control). No further hormonal manipulations were performed after hatching. Sexual behavior was recorded in males at the age of 6 weeks. Estradiol- and diethylstilbestrol-treated males exhibited a total suppression of copulatory behavior. After behavioral tests, all males were sacrificed and brain sections processed for vasotocin immunocytochemistry. Significant decrease in the density of vasotocin immunoreactivity was detected in the medial preoptic nucleus, in the bed nucleus of stria terminalis, and in the lateral septum of diethylstilbestrol-treated males. The magnocellular vasotocin neurons were, in contrast, not affected. In conclusion, the present data demonstrate that embryonic treatment with diethylstilbestrol induces a full sex reversal of behavioral phenotype as well as a significant decrease of vasotocin expression in the preoptic-limbic region in male Japanese quail. Therefore, the parvocellular vasotocin system could represent an optimal model to investigate the effects of pollutants on neural circuits controlling reproductive functions.

Analysis of Variance↗
PubMed2004

Evidence that the effect of melanocortins on female sexual behavior in preoptic area is mediated by the MC3 receptor; Participation of nitric oxide.

alpha-MSH is involved in reproductive processes and can regulate the expression of lordosis, an important component of female reproductive behavior in rats and many other species. In this study, we investigated the effects of MSH peptides on lordosis behavior when injected in medial preoptic area (POA) of ovariectomised rats primed with estradiol. The results show an increase in lordotic activity after bilateral administration of alpha-MSH and gamma-MSH. Interestingly, the treatment with the MC4 receptor antagonist HS014 did not block the stimulatory effect of alpha-MSH. Moreover, the injection of HS014 did not itself modify the lordosis quotient. Nitric oxide has been suggested to play a crucial role in the regulation of lordosis behavior via stimulation of guanylyl cyclase to synthesize cGMP. In order to determine the participation of NO in the effect of the melanocortins, another group of rats were treated with L-NAME, an inhibitor of NOS, alone or 15 min before the injection of alpha-MSH or gamma-MSH. The injection of L-NAME into the POA of E-primed rats 15 min before the test for sexual receptivity did not modify significantly the lordosis quotient at the two doses examined. The treatment with L-NAME at the lowest dose completely abolished the stimulatory effect of alpha-MSH and gamma-MSH on sexual behavior. The results indicate that the effects of MSH peptides on female sexual behavior in this area are mediated through specific MC receptor, that could be the MC3 receptor and that NO mediates the melanocortins effects.

Animals↗
PubMed2005

Anabolic androgenic steroids and forebrain GABAergic transmission.

Anabolic androgenic steroids are synthetic derivatives of testosterone designed for therapeutic purposes, but now taken predominantly as drugs of abuse. The most common behavioral effects associated with anabolic androgenic steroid use are changes in anxiety, aggression and reproductive behaviors, including the onset of puberty and sexual receptivity. GABAergic circuits in the forebrain underlie these behaviors and are regulated by gonadal steroids. Work from our laboratories has shown that the expression and function of GABA(A) receptors in the rat and mouse forebrain varies between the sexes and across the estrous cycle. We have also shown that there are significant changes in GABA(A) receptor expression that occur with the progression through puberty to adulthood. Because GABAergic systems are both steroid-sensitive and critical for the expression of behaviors altered with anabolic androgenic steroid use, forebrain GABA(A) receptors are an attractive candidate to assess how molecular actions of anabolic androgenic steroids may be translated to known behavioral outcomes. Our studies demonstrate that anabolic androgenic steroids elicit both acute modulation of GABA(A) receptor-mediated currents, as well as chronic regulation of GABA(A) receptor expression and forebrain GABAergic transmission. Because anabolic androgenic steroid use has now become prevalent not only among adolescent boys, but in an increasing number of adolescent girls, we have also been particularly interested in determining age- and sex-specific effects of anabolic androgenic steroids. Our data show that the effects of chronic anabolic androgenic steroid exposure can be greater for adolescent than adult animals and are more marked in females than in males. These data have particularly important implications with respect to studies we have done demonstrating that chronic anabolic androgenic steroid exposure alters the onset of puberty, estrous cyclicity and sexual receptivity.

Adolescent↗
PubMed1998

Injection of oxytocin into the medial preoptic-anterior hypothalamus increases ultrasound production by female hamsters.

Recent studies of hamsters have documented the facilitation of lordosis and other sociosexual responses by injections of oxytocin (OXT) into the medial preoptic area-anterior hypothalamus (MPOA-AH). These data suggest the regulation of social interaction and bonds by OXT. In turn, this suggests that OXT could act in the MPOA-AH to control other behaviors involved in the initiation or maintenance of social contact, including the ultrasonic vocalizations that female hamsters use to alert and attract potential mates. To test this possibility, we compared the ultrasound rates of 11 naturally estrous hamsters before and after injections of OXT (200 ng/200 nl of saline) or saline (200 nl) into the MPOA-AH. The data revealed a clear facilitation of ultrasound rate 30 min after OXT treatment. This result suggests the modulation of ultrasound rate by endogenous OXT acting within the MPOA-AH. It extends the range of social behaviors sensitive to control by OXT and supports the possibility that OXT acts within the MPOA-AH to facilitate a variety of behaviors involved in the establishment or maintenance of the social interactions required for successful reproduction. At the same time, these data extend earlier observations linking ultrasound production to the MPOA-AH, and begin to describe the peptidergic mechanisms controlling this form of reproductive behavior.

Animals↗
PubMed2004

Evolution and comparative genomics of odorant- and pheromone-associated genes in rodents.

Chemical cues influence a range of behavioral responses in rodents. The involvement of protein odorants and odorant receptors in mediating reproductive behavior, foraging, and predator avoidance suggests that their genes may have been subject to adaptive evolution. We have estimated the consequences of selection on rodent pheromones, their receptors, and olfactory receptors. These families were chosen on the basis of multiple gene duplications since the common ancestor of rat and mouse. For each family, codons were identified that are likely to have been subject to adaptive evolution. The majority of such sites are situated on the solvent-accessible surfaces of putative pheromones and the lumenal portions of their likely receptors. We predict that these contribute to physicochemical and functional diversity within pheromone-receptor interaction sites.

Animals↗
PubMed1996

Feeding-induced stimulation of luteinizing hormone secretion in male rhesus monkeys is not dependent on a rise in blood glucose concentration.

Recent studies have suggested a role for glucose availability in the central control of reproductive function. Various experimental paradigms have shown that a large pharmacological reduction in circulating or cellular glucose levels can suppress LH secretion, ovulation, and reproductive behavior. In contrast, states of undernutrition, which are also associated with a suppression of reproductive function, are accompanied by very mild changes in circulating glucose levels. In monkeys, 1 day of fasting leads to a significant suppression of LH secretion before any significant change in blood glucose levels, and by 2 days of fasting, circulating glucose levels only decrease by about 20%. Refeeding a normal meal after 2 days of fasting results in a restoration of euglycemia and a rapid stimulation of LH secretion. To test the hypothesis that physiological changes in glucose levels occurring during brief periods of fasting and refeeding can modulate LH secretion, we provided monkeys that had been fasted for 2 days with meals that differed in the ability to raise blood glucose levels. Meals consisting of mixed nutrients, carbohydrate only, or protein and fat were provided to monkeys through indwelling gastric cannulas. Mixed nutrient infusions and carbohydrate infusions caused a rise in blood glucose as well as a robust stimulation of LH secretion. However, protein and fat meals also stimulated LH secretion, even though no rise in blood glucose concentrations occurred. Thus, the restoration of pulsatile LH secretion when fasted animals are refed is not dependent on an elevation in circulating glucose levels. These results do not support the hypothesis that physiological changes in circulating glucose levels play a necessary role in mediating the changes in LH secretion that occur with fasting and refeeding. Alternatively, these results support the hypothesis that the availability of metabolizable fuels, regardless of their nature, provides a critical cue that regulates the central drive to the reproductive axis under physiological conditions of fasting and feeding.

Animal Feed↗
PubMed2000

Sexual and fertility behaviors of American females aged 15-19 years: 1985, 1990, and 1995.

OBJECTIVES: This study characterized changes in sexual and reproductive behaviors from 1985 through 1995 among American females aged 15 to 19 years and related these changes to family factors. METHODS: Nationally representative sample survey data from the 1995 National Survey of Family Growth were analyzed with Weibull hazards models of age at first intercourse and first pregnancy and with logistic regression models of contraceptive use at first intercourse and pregnancy outcome. RESULTS: Improvements in the family socioeconomic situations of young women have lessened the risk of teen motherhood, while changes in family structure have increased the risk. Young women whose parents have more than a high school education, who live with both parents, and who attend church delay the timing of first sexual intercourse and are more likely to use a contraceptive. CONCLUSIONS: The trend of increases in teenage motherhood has ended owing to a halt in increases in the proportion of sexually active young women and substantial improvement in contraception, with the greatest improvements among those from advantageous family situations.

Adolescent↗
PubMed1995

Potential interactions between estrogen receptor and thyroid receptors relevant for neuroendocrine systems.

Environmental signals can profoundly affect reproductive behavior, physiology and responses to steroids. One consequence of nutritional or temperature stress is altered plasma concentrations of thyroid hormone. Recent in vivo and in vitro data indicate that manipulations of estrogen and thyroid hormone levels can alter each other's functions. One possible mechanism for interaction may be that thyroid and estrogen receptors bind to parts of the same hormone response elements of target genes and compete with each other, thus serving to integrate environmental signals with neuroendocrine responses.

Animals↗