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At least 451 records · Page 25Linked to original sources
PubMed2003

Developmental, behavioral, and reproductive effects experienced by Japanese medaka (Oryzias latipes) in response to short-term exposure to endosulfan.

Japanese medaka (Oryzias latipes) were exposed to concentrations of 0.01, 0.10, and 1.0 microg/L of the pesticide endosulfan for 24h beginning either 4-6h postfertilization or 4-6h posthatch to determine effects on hatching time, growth, mobility, foraging ability, and reproduction. Eggs exposed to endosulfan took longer to hatch, and the resulting fry were smaller at 1 week of age and had decreased mobility at 2 weeks of age. Upon reaching sexual maturity, these individuals also produced fewer eggs, and these eggs took significantly longer to hatch. Medaka exposed to endosulfan shortly after hatching did not differ in early mobility or foraging ability. Interestingly, upon reaching sexual maturity, these individuals produced more eggs than did unexposed females. The observed effects were not dose-dependent, with medaka exposed to intermediate concentrations of endosulfan (0.10 microg/L) exhibiting the greatest response. These results suggest that short-term exposure to environmentally relevant concentrations of a common pesticide may have long-term effects on growth, behavior, and reproduction in fish.

Animals↗
PubMed2004

Territorial aggression, circulating levels of testosterone, and brain aromatase activity in free-living pied flycatchers.

Testosterone (T) is a critical endocrine factor for the activation of many aspects of reproductive behavior in vertebrates. Castration completely eliminates the display of aggressive and sexual behaviors that are restored to intact level by a treatment with exogenous T. There is usually a tight correlation between the temporal changes in plasma T and the frequency of reproductive behaviors during the annual cycle. In contrast, individual levels of behavioral activity are often not related to plasma T concentration at the peak of the reproductive season suggesting that T is available in quantities larger than necessary to activate behavior and that other factors limit the expression of behavior. There is some indication from work in rodents that individual levels of brain aromatase activity (AA) may be a key factor that limits the expression of aggressive behavior, and in agreement with this idea, many studies indicate that estrogens produced in the brain by the aromatization of T may contribute to the activation of reproductive behavior, including aggression. We investigated here in pied flycatcher (Ficedula hypoleuca) the relationships among territorial aggression, plasma T, and brain AA at the peak of the reproductive season. In a first experiment, blood samples were collected from unpaired males holding a primary territory and, 1 or 2 days later, their aggressive behavior was quantified during standardized simulated territorial intrusions. No relationship was found between individual differences in aggressive behavior and plasma T or dihydrotestosterone levels but a significant negative correlation was observed between number of attacks and plasma corticosterone. In a second experiment, aggressive behavior was measured during a simulated territorial intrusion in 22 unpaired males holding primary territories. They were then immediately captured and AA was measured in their anterior and posterior diencephalon and in the entire telencephalon. Five males that had attracted a female (who had started egg-laying) were also studied. The paired males were less aggressive and correlatively had a lower AA in the anterior diencephalon but not in the posterior diencephalon and telencephalon than the 22 birds holding a territory before arrival of a female. In these 22 birds, a significant correlation was observed between number of attacks/min displayed during the simulated territorial intrusion and AA in the anterior diencephalon but no correlation was found between these variables in the two other brain areas. Taken together, these data indicate that the level of aggression displayed by males defending their primary territory may be limited by the activity of the preoptic aromatase, but plasma T is not playing an important role in establishing individual differences in aggression. Alternatively, it is also possible that brain AA is rapidly affected by agonistic interactions and additional work should be carried out to determine whether the correlation observed between brain AA and aggressive behavior is the result of an effect of the enzyme on behavior or vice versa. In any case, the present data show that preoptic AA can change quite rapidly during the reproductive cycle (within a few days after arrival of the female) indicating that this enzymatic activity is able to regulate rapid behavioral transitions during the reproductive cycle in this species.

Aggression↗
PubMed1993

[Attitudes and behavior for reproductive health].

Educational interventions represent an alternative for the reproductive well-being. The objective of this investigation was to identify in a mexican community, attitudes and behaviors related to reproductive health, with the goal of implementing a specific health education program. The study population consisted of women between 12 and 44 years old, living in non-residential areas of the Delegation Miguel Hidalgo, D.F. Variables of interest were analyzed only in women with parity (n = 300). Data were collected through interview. The mean age was 31 +/- 8 years. 93.3% were married or in consensual union. 63% had elementary, junior high or prevocational studies. 89% answered that would visit the doctor before considering a pregnancy (junior high+, p < .05), 99% would seek prenatal care if they were pregnant, and 92.7% would have a hospital delivery (parity < or = 3, p < .003). 69.5% had a preconceptional visit before their last pregnancy and 89.9% received prenatal care (junior high+, p < .008). 92.5% had only hospital deliveries (< or = 30 years, p < .05, junior high+, p < .0001, primigravida p < .002, with institutionalized medical services, p < .001), 1.7% had only out-of-hospital deliveries, and 5.8% both. Agreement between attitudes and behaviors are presented. An educational program consisting of confirmation and support to positive attitudes, values and beliefs, and reinforcement to decision making, will result in a final behavior: early assistance to medical care.

Adolescent↗
PubMed1996

In vivo regulation of central nervous system progesterone receptors: cocaine induces steroid-dependent behavior through dopamine transporter modulation of D5 receptors in rats.

To characterize the membrane pathway by which the cocaine-sensitive dopamine transporter (DAT) modulates progesterone receptor activation, steroid-dependent behavior lordosis was used in estrogen-primed ovariectomized Sprague-Dawley rats with stereotaxic implanted third ventricle cannulas. Lordosis in response to solicitous males was observed in females after intercerebral ventricular administration of DAT antagonists WIN35,428 (80 ng) and cocaine (0.016-1.6 micrograms). Significantly, antisense oligonucleotides (AS) to DAT mRNA also induced reproductive behavior. In contrast, the D1-D2 receptor membrane-repopulation inhibitor N-ethoxycarbonyl-2 ethoxy-1,2-dihydroquinoline and the D1-like antagonist SCH23390 blocked cocaine-inducible behavior. Further, facilitation of behavior by AS to the DAT was suppressed by N-ethoxycarbonyl-2 ethoxy-1,2-dihydroquinoline. Behavior was not dependent on D2 receptors, since animals pretreated with the D2 antagonist sulpride displayed lordosis after cocaine challenge. Antisense oligonucleotides to D5 but not D1 dopamine receptor mRNA suppressed reproductive behavior associated with cocaine. Microinjections of cocaine to the ventromedial nucleus (VMN) but not arcuate nucleus or preoptic area potentiated lordosis, suggesting the functional presence of DAT in the VMN. Finally, cocaine facilitation of behavior was blocked by both antiprogestin RU486 and progesterone receptor AS microinjected into either the third ventricle or the VMN. Collectively, the data provide strong evidence for cocaine modulation of reproductive behavior through presynaptic cocaine-sensitive dopamine transporters and postsynaptic D5 dopamine receptor mediation of progesterone receptor-dependent behavior in rat central nervous system.

Animals↗
PubMed2000

An evaluation of lekking behavior in the fiddler crab Uca spp.

The reproductive behavior of Uca spp. has been extensively studied, especially the relationships between the dimorphically enlarged male claw and reproductive success. In contrast, little is known about the apparent congregations of adult males in marsh areas lacking vegetative cover where they engage in behaviors thought to attract mates. Similar congregations and displays in avian and mammalian species are termed 'leks.' In order to test the hypothesis that open-area assemblages of Uca spp. are functioning as leks, we examined the sex ratios, juvenile/adult ratios, and the percentage of time that adult males spend eliciting reproductive behaviors within open and vegetated areas of marsh habitats. Moreover, to evaluate whether differences in sediment-based food resources could explain open-area aggregations, we compared substratum organic content of open and vegetated areas of marsh habitats. Substrate was also examined to determine if grain size composition varied between open and vegetated areas and might preclude the construction of breeding burrows in vegetated areas of the marsh. Three species of Uca from four marsh habitats in biogeographically distinct regions of North America were sampled including Dauphin Island, Alabama, Hunting Island, South Carolina, Saxis, Virginia, and Wallops Island, Virginia. Comparisons of male/female and juvenile/adult ratio means indicated that greater numbers of adult males occurred in open areas of all marshes. In addition, adult males allocated significantly greater time to reproductive behaviors in open rather than in vegetatively covered areas across-all biogeographic regions and among all species. Food levels (sediment organic content) in open areas were equal to or less than sediment organic contents in vegetated areas in marsh habitats at Dauphin Island and Hunting Island, the two marshes where the variable was examined. Similarly, substratum granulometry analysis revealed no significant differences between open and vegetatively covered areas of the marshes at Dauphin Island or Hunting Island that might influence choice of burrow location. Collectively, these observations support the hypothesis that lek behavior is an integral component of the reproductive repertoire in Uca spp.

Journal Article↗
PubMed1995

Species differences in estrogen receptor and progesterone receptor-mRNA expression in the brain of sexual and unisexual whiptail lizards.

Circulating concentrations of gonadal steroid hormones and reproductive behavior in female vertebrates vary as a function of ovarian state. Steroids secreted by the ovary, specifically estrogen and progesterone, influence the expression of behaviors associated with reproduction by intracellular sex steroid receptors located in specific regions of the brain. Using in situ hybridization, we analyzed estrogen receptor and progesterone receptor messenger RNA expression in several brain regions of ovariectomized, vitellogenic, and postovulatory individuals from two species of whiptail lizards (Cnemidophorus uniparens and C. inornatus). Although these species are genetically very similar, they differ in two aspects of their reproductive biology: (i) the unisexual C. uniparens alternate between expressing female-typical and male-like pseudosexual behaviors while female C. inornatus normally express only female receptive behavior, and (ii) circulating estradiol concentrations in reproductively active female C. uniparens are approximately five-fold lower than in reproductively active female C. inornatus. We found that the regulation of sex steroid receptor gene expression was region specific, with receptor-mRNA expression being increased, unchanged, or decreased during vitellogenesis depending on the area. Furthermore, several species differences in the amount of sex steroid receptor-mRNA were found that may be relevant to the species differences in circulating estrogen concentrations and sexual behavior.

Animals↗
PubMed1987

Pinealectomy blocks vernal courtship behavior in red-sided garter snakes.

Male red-sided garter snakes (Thamnophis sirtalis parietalis) court only on emergence from winter dormancy. The salient proximate factor responsible for the initiation of courtship behavior appears to be warm ambient temperatures subsequent to sustained exposure to cold temperatures. In the present study, autumn-captured garter snakes were pinealectomized or sham-pinealectomized 1-2 weeks prior to hibernation. After 17 weeks of maintenance in several ambient lighting and temperature conditions, all males were tested for the presence of courtship behavior. No pinealectomized animals exhibited any indications of reproductive behavior, whereas 53% of sham-pinealectomized males actively courted females. Photoperiod did not influence the prevalence of mating behavior. These results suggest that the pineal gland mediates non-photoperiodic seasonal information in the garter snake. This is the first demonstration, in any vertebrate species, that the pineal gland can directly influence reproductive behavior.

Animals↗
PubMed1992

Blurred edges to population policies.

Fertility is now below replacement level in most European countries, especially the industrialized ones. In the last 20 years, several countries have developed or improved pronatalist programs containing incentives that are designed to motivate couples to have a 2nd and especially a 3rd child, to maintain a stable population. The WHO Sexuality and Family Planning Unit called a short consultation on this subject last October. What actually constitutes a pronatalist population program and the connections between public policies and private reproductive behavior were not very clear. Nor is it easy to assess the longer--term demographic effects of pronatalist policies or what influences their effectiveness. The outcome usually reflects the country's history, cultural and religious traditions, changes in lifestyle, and the value given to the family and children. Incentives are defined as monetary or nonmonetary inducements to voluntary reproductive behavior that conforms to specified population policies. They may be small or large, in cash or kind, parity-specific or income-linked, immediate or developed, one-time or incremental, or any combination of these. Disincentives are negative sanctions that are either incurred or thought likely as a result of violating the policy. But both incentives and disincentives are difficult to define. Pronatalist policies designed to encourage early marriage and larger families, thereby raising the future total fertility rate should not be confused with traditional social welfare policies designed simply to ease the burden of childbearing. Some policies have both demographic and social welfare aims. Strong pronatalist policies may be linked with restrictions on contraceptive availability and legal abortion. Moreover, other public policies affecting social security, education, employment, housing, regional planning and the emancipation of women may unintentionally influence demographic behavior. Population policies are the product of politics. Often written in ambiguous language and intended to affect society as a whole, they still depend for their outcome on microlevel changes in a couple's perceptions of the costs and benefits of having children. In theory, they can be carried out in many ways but in practice such policies are severely limited by administrative, political, technological, economic, and ethical constraints. One difficulty is that governments is rarely enunciate precise goals. Their approach may range from noninterference in private reproductive behavior to total coercion using controls ranging from traditional cultural influences to imposition of fertility regulations. In some countries, fertility rates have increased briefly (in terms of period rates) following introduction of pronatalist policies. However, it is not clear how the rates were influenced, particularly in the case of parities 1, 2, and 3. A forthcoming report will describe experiences in Bulgaria, France, Germany, Sweden, and Norway.

Developed Countries↗
PubMed1998

Neuroendocrine suppression of female courtship in a wild passerine: corticotropin-releasing factor and endogenous opioids.

During emergencies in their natural environments, vertebrates initiate coping mechanisms that redirect behavior away from nonessential activities and towards survival. Reproductive behaviors are suppressed. Evidence from field studies on passerine birds shows that this inhibition may not depend on the suppression of gonadal sex steroids, since during the breeding season they remain elevated despite activation of the stress response. We hypothesize that an alternate, central mechanism mediates the inhibition of reproductive behavior during stress in passerines. In this study, we tested the intracerebroventricular effects of endogenous opioids and corticotropin-releasing factor (CRF), neuropeptides implicated in the stress response, on courtship behavior in wild-caught female white-crowned sparrows. Beta-endorphin (beta-EN) significantly inhibited copulation solicitation, an estrogen-dependent courtship display, 30 min after treatment. Naloxone, an opioid antagonist, enhanced the behavior. CRF caused a suppression of solicitation that was reversible by pretreatment with naloxone, suggesting an intermediary role for endogenous opioids in CRF-induced suppression of courtship. The effects of beta-EN and CRF on solicitation appear to be independent of any general effects on locomotor activity. These results support our hypothesis that stress neuropeptides orchestrate coping behaviors in wild birds.

Adaptation, Psychological↗
PubMed2002

Sex hormones and neural mechanisms.

Sex steroids play important and diverse roles in the regulation of structure and function of the central nervous system. Early in life, steroids shape the structure of sensitive areas of the brain, especially those involved in the control of reproductive behavior and ovarian function. Original studies demonstrating organizing effects of steroids on the brain were carried out in rodents, but more recently these studies have been extended to primates, including humans. Throughout life, sex steroids regulate neural function by influencing steroid receptor-bearing neurons and by influencing neurons via steroid receptor-independent mechanisms. Sex steroid receptors have been identified in the brain, especially in the phylogenetically ancient structures that regulate reproductive behavior. Sex steroids that affect neural function can originate peripherally from the brain and/or adrenal gland, and can be synthesized within the brain itself. A number of neurally active progestogens and androgens are synthesized de novo in the brain, and estrogens can be converted within the brain from androgens by the enzyme aromatase. Thus, ovarian and central nervous system sex steroids play important roles in regulating reproductive behavior by regulating neural structure and function.

Androgens↗
PubMed1992

Differential projections of the anterior and posterior regions of the medial amygdaloid nucleus in the Syrian hamster.

The medial nucleus of the amygdala is important for the neural control of reproductive behavior in the adult male Syrian hamster. Two types of signals are essential for this behavior, chemosensory stimuli and gonadal steroids; these signals appear to be received in different parts of the medial nucleus. The anterior region receives input from olfactory and vomeronasal systems, both of which are required for this behavior, whereas the posterior region receives gonadal hormone inputs. Behavioral studies have also suggested a functional differentiation of these two areas; electrolytic lesions of the anterior, but not the posterior, part eliminates normal sexual behavior. In this study, the efferent projections of the anterior and posterior divisions of the medial nucleus of the amygdala in the Syrian hamster were analyzed throughout the forebrain after injections of the anterograde neuronal tracer, Phaseolus vulgaris-leucoagglutinin. Neurons of the anterior, but not the posterior, medial nucleus, were found to project to numerous olfactory bulb projection areas and to the ventral striatopallidal complex. Within areas of the chemosensory circuitry that control reproductive behavior, the anterior region of the medial nucleus projects to the intermediate part of the posterior bed nucleus of the stria terminalis and the lateral part of the medial preoptic area, whereas the posterior region of the medial nucleus projects to the medial parts of these areas. Differences in targets were also observed in the ventromedial nucleus of the hypothalamus where the anterior region projects to the core while the posterior part projects to the shell of this nucleus. Furthermore, reciprocal projections between the anterior and posterior regions of the medial nucleus were observed. Taken together, these studies support the hypothesis that the anterior and posterior regions of the medial amygdaloid nucleus provide substantially different contributions to the control of reproductive behaviors.

Amygdala↗
PubMed2004

Identification of 3beta,5beta-tetrahydroprogesterone, a progesterone metabolite, and its stimulatory action on preoptic neurons in the avian brain.

We have demonstrated recently that the quail brain possesses the cholesterol side-chain cleavage enzyme (cytochrome P450scc) and 3beta-hydroxysteroid dehydrogenase/Delta(5)-Delta(4)-isomerase (3beta-HSD) and produces pregnenolone, pregnenolone sulfate and progesterone from cholesterol. The present study was therefore conducted to investigate progesterone metabolism in the brain of adult male quails. Employing biochemical techniques combined with HPLC and TLC analyses, the conversion of progesterone to 3beta,5beta-tetrahydroprogesterone (3beta,5beta-THP) via 5beta-dihydroprogesterone (5beta-DHP) was found in the brain. There was a clear regional difference in progesterone metabolism. The formation of 3beta,5beta-THP was high in the diencephalon and cerebrum and low in the cerebellum. Based on such a region-dependent formation of 3beta,5beta-THP, the action of this progesterone metabolite on preoptic neurons in the diencephalon was then investigated electrophysiologically using a brain slice preparation of the adult male. 3beta,5beta-THP significantly increased, in a dose-related way, the spontaneous firing activity of subsets of preoptic neurons. The stimulatory effect of 3beta,5beta-THP was greater than that of progesterone and its threshold concentration ranged between 10(-6) and 3x10(-6) M. In 33% of cells in the preoptic area, however, 3beta,5beta-THP did not change the spontaneous firing activity even at the high concentration, 10(-5) M. Because preoptic neurons are considered to be involved in the regulation of a variety of male reproductive behaviors, 3beta,5beta-THP may regulate some reproductive behavior through the mechanism that provokes such a stimulation.

Action Potentials↗
PubMedDate not supplied

Hormonal and genetic influences underlying arousal as it drives sex and aggression in animal and human brains.

Estrogen treatment induces transcription and increases excitability and reproductive behavior. Estrogens provide the structural basis for increased synaptic activity and greater behavior-facilitating output. Administration of progesterone amplifies the effect of estrogens on mating behavior. The role of GnRH is to synchronize reproductive behavior with the ovulatory surge of LH. A causal connection can be charted from one individual gene to human social behavior, but only via six causal links. Glia, meninges and neurons may participate, under the influence of sex hormones, in the direction of sex behavior. Neural and genetic mechanisms for motivation may lead to biological understanding of functions that apply to the most primitive aspects of human mental functioning. With respect to aggression, besides testosterone and its metabolites, serotonergic projections to the forebrain play an important role.

Aggression↗
PubMed1999

Androgenic regulation of hypothalamic aromatase activity in prepubertal and postpubertal male golden hamsters.

Doses of testosterone that fully activate male reproductive behavior in castrated adult male hamsters fail to elicit mounting and intromissions in prepubertal castrates, even when circulating levels of testosterone are equivalent in the two age groups. We hypothesize that this differential responsiveness to testosterone is mediated at least in part by the efficacy with which testosterone in the hypothalamus is aromatized to estradiol, an important hormone mediating male sexual behavior. Therefore, hypothalamic aromatase activity, as measured by the conversion of [3H]testosterone to [3H]estradiol in tissue homogenates, was assessed in four separate experiments: 1) intact prepubertal and adult male golden hamsters, 2 and 3) castrated adult or prepubertal males that received either a 0- or 2.5-mg dose of testosterone, and 4) castrated adult and prepubertal males treated with the 2.5-mg dose oftestosterone. These studies demonstrate that hypothalamic aromatase activity is significantly higher in adult males compared with prepubertal males, and that hypothalamic aromatase activity is increased by testosterone to the same extent in both the adult and prepubertal male hamster. Therefore, the failure of testosterone-treated castrated prepubertal male hamsters to engage in the full suite of male reproductive behaviors is not due to the inability of testosterone to be converted into estradiol in the hypothalamus. Differences in the ability of testosterone to increase aromatase activity in other brain regions, or differences in the action of testosterone and/or estradiol on other cellular processes must account for the inability of testosterone to facilitate male reproductive behavior in juvenile males.

Aging↗
PubMed2003

Relative contributions of the male and the female to sexual behavior and reproductive success in the Japanese quail (Coturnix japonica).

Two contrasting investigative techniques provided evidence consistent with the interpretation that female quail (Coturnix japonica) regulate male copulatory behavior by the duration of their immobility and through this behavioral mechanism they also control the rate of fertilization of their eggs. In Experiment 1, copulation tests with males and females from different genetic lines showed that the type of female that participated in a copulatory test significantly influenced the latency of the male's grab, mount, and cloacal contact responses and also determined the efficiency of the male's copulatory behavior. These measures of male performance were correlated with female immobility in Experiment 2, which used a more homogeneous population of quail. Furthermore, 2 of these measures (copulatory efficiency and the latency to make cloacal contact) were correlated with fertilization rate.

Animals↗