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PubMed1988

Methoxychlor induces estrogen-like alterations of behavior and the reproductive tract in the female rat and hamster: effects on sex behavior, running wheel activity, and uterine morphology.

The current investigation was designed to determine if the pesticide methoxychlor (M) mimicked the effects of estrogen in the brain and on behavior. Running wheel activity (RWA) and sex behaviors were evaluated in this study because the role of estrogen in the regulation of these behaviors has been thoroughly established. M exposure at 400 mg/kg/day (90% pure) induced high levels of acyclic RWA and persistent vaginal estrus in the female rats. Following ovariectomy (ovx), RWA declined precipitously in controls but remained at high levels in M-treated-ovx females. M also produced estrogen-like alterations of the uterine endometrial epithelium, the ovary, and growth after ovx. In another study, ovx female rats were dosed with M at 200 mg/kg/day and then with progesterone (P). P acts as an antiestrogen and specifically suppresses estrogen-induced RWA. P blocks the synthesis of estrogen receptors in the CNS and reproductive tract but does not lower RWA induced by nonestrogenic mechanisms. After 14 days of M administration RWA was increased fourfold over the ovx-oil-treated females. Subsequently, P injections reduced RWA levels far below those seen when the ovx-M-treated rats were injected with oil. The P-induced decline represents a 95% inhibition of the M-induced increase in RWA. Subsequently, M-treated-ovx rats and hamsters were injected with P and tested for their ability to display reproductive behaviors when paired with a stud male. Female sexual behaviors are induced by the administration of estrogen followed by progesterone. In this study the M-treated females displayed reproductive behaviors, in contrast to the oil-treated rats and hamsters. The observation that the high levels of RWA induced by methoxychlor treatment in ovx rats can be suppressed by concurrent progesterone injections demonstrates that the increase in RWA is due to the estrogenic effects of methoxychlor on the CNS. The fact that methoxychlor, followed by P injections, induces behavioral estrus in the rat and hamster extends this estrogenicity to other areas in the CNS.

Animals↗
PubMed1980

[Experimental studies on various model material. 3. Dimensional behavior and reproductive fidelity as compared to those of elastomers].

Bandless impressions of tooth stumps obtained with the model materials Begolith, Dentaloc, Tewestone, Impredur and Keramid-Cement in combination with the elastic impression materials Silcoflex, Sanal/Silcoflex, Xirux/Xirux F and Impergum were studied in relation to dimensional behavior and reproduction fidelity. With reference to these parameters as well as to the hardness and abrasive behavior of the model materials after processing at various temperatures, recommendations are made for the optimum combination of these two groups of materials in practice.

Acrylic Resins↗
PubMed1992

Evolutionary precedents for behavioral actions of oxytocin and vasopressin.

It is clear that the behavioral actions of oxytocin and vasopressin in mammals are not newly acquired, but have evolutionary antecedents. Injection studies with fish, amphibians, reptiles, and birds indicate that AVT can activate certain reproductive behaviors. The strongest evidence that AVT acts centrally to control reproductive behaviors comes from research on T. granulosa. In this amphibian, injections of AVT agonists activate courtship behaviors (amplectic clasping) in males and egg-laying behaviors in females, whereas injections of AVT antagonists inhibit the behaviors. Also, in Taricha males, AVT concentrations in specific brain areas are associated with the expression of courtship behaviors. Several conclusions about steroid-peptide interactions can be drawn, based on research with this amphibian. First, gonadal steroid hormones act to maintain the behavioral actions of AVT in both males and females. In Taricha, gonadectomy abolishes and steroid implants restore AVT-induced courtship in males and egg-laying in females. Second, gonadal steroids maintain the behavioral actions of AVT, in part, by modulating AVT receptor numbers on target neurons. In Taricha males and females, gonadectomy reduces AVT receptor concentrations (but not binding affinity) in certain brain areas (amygdala pars lateralis) and not others. Third, the type of gonadal steroid determines whether AVT elicits male-like or female-like reproductive behaviors. Ovariectomized Taricha females respond to AVT injections with egg-laying behaviors when implanted with estradiol and with male-like amplectic clasping when implanted with dihydrotestosterone. Fourth, the masculinization of AVT-induced behaviors in females most likely reflects site-specific actions of androgens on AVT-synthesizing neurons. In Taricha, AVTir concentrations in the optic tectum are sexually dimorphic (higher in males than females) and reach peak levels in males during the breeding season. Fifth, AVT content in specific brain areas increase as a function of performing the behaviors. In Taricha, AVTir concentrations in DPOA, CSF, and ventral infundibulum are higher in males that exhibit courtship behaviors than in males that do not. These conclusions illustrate how steroid-peptide interactions in the control of behaviors entail multiple neuroanatomical sites and neurochemical actions.

Animals↗
PubMed1994

Gonadotropin-releasing hormone and its receptors in rat brain.

Since the chemical identification of gonadotropin-releasing hormone (GnRH) in 1971, significant progress has been made in understanding the mechanisms by which GnRH action is mediated in the anterior pituitary. In contrast, relatively little information is available which identifies the intracerebral sites and mechanisms of action of GnRH in the brain. Early immunohistochemical studies of GnRH distribution in the central nervous system, together with behavioral and electrophysiological experiments, suggested that GnRH functioned as a neurotransmitter and was, possibly, involved in the expression of reproductive behaviors. The subsequent identification and characterization of GnRH receptors in the brain further strengthened the view that GnRH caused specific effects in select regions of the brain known to be involved in the neuroendocrine regulation of the anterior pituitary and in the generation of reproductive behaviors. After the mouse pituitary GnRH receptor was cloned it became possible to identify brain neurons which contained the GnRH receptor mRNA. Comparison of the locations of the GnRH peptide, the GnRH receptor protein, and the neurons which contain the GnRH receptor mRNA suggests that the GnRH neuronal system itself can potentially provide a direct link between the neuroendocrine regulation of anterior pituitary function and the intracerebral regulation of reproductive behaviors; furthermore, it is possible that the GnRH neuronal system takes an active part in intracerebral feedback loop systems between the mediobasal hypothalamus and the septum-diagonal band which regulate GnRH release from the median eminence.

Amino Acid Sequence↗
PubMed1995

Effects of opioid peptides on the electrical activity of preoptic and hypothalamic neurons in the quail brain.

We have recently isolated three opioid peptides, i.e., Met- and Leu-enkephalins and Met-enkephalin-Arg6-Phe7, from the avian brain. In the present study, therefore, effects of these endogenous opioid peptides on the electrical activity of preoptic and hypothalamic neurons of the adult male Japanese quail were examined using a brain slice preparation. All of the three opioid peptides inhibited the spontaneous firing activities of subsets of neurons in the preoptic area and the paraventricular nucleus in the hypothalamus. Threshold concentrations for the inhibitory action were between 10(-7) and 10(-6) M in Met- and Leu-enkephalins and approximately 10(-6) M in Met-enkephalin-Arg6-Phe7, respectively. In a few cells in these brain areas, however, Leu-enkephalin rather potentiated the spontaneous activities, resulting in an increase of firing rates or a decrease of interburst intervals. The inhibitory effect of Met-enkephalin was completely blocked by naloxone, an opioid receptor antagonist, but not affected by bicuculline, a gamma-aminobutyric acid A (GABAA) receptor antagonist. These results suggest that there are functional opiate receptors in subsets of preoptic/hypothalamic neurons and that one of their main physiological functions in these areas is an inhibition of neuronal activities. Because these brain regions are considered to be involved with the regulation of a variety of male reproductive behaviors, opioid peptides may regulate some reproductive behavior through the mechanism that provokes such an inhibition.

Action Potentials↗
PubMed1997

Inhibitory role of opioid peptides in the regulation of aggressive and sexual behaviors in male Japanese quails.

We have recently isolated three opioid peptides, i.e., Met- and Leu-enkephalins and Met-enkephalin-Arg6-Phe7, from the avian brain. Furthermore, electrophysiological studies have shown that the dominant effect of these enkephalins on preoptic and hypothalamic neurons is an inhibition of neuronal activities in the male Japanese quail. The hypothalamus and preoptic area are known to be involved in the control of male reproductive behaviors, such as aggressive and sexual behaviors. To determine the functional role of opioid peptides in these reproductive behaviors, therefore, the present study was undertaken using adult males of the Japanese quail. We examined behavioral changes following an injection of naloxone (0.2, 2.0, and 20.0 nmol), a nonselective opioid receptor antagonist, or D-Ala2-Met5-enkephalinamide (DALA; 0.2, 2.0, and 20.0 nmol), a selective delta opioid receptor agonist, into the preoptic and anterior hypothalamic regions. Naloxone treatment showed a significant increase in the frequency of several aggressive actions and the effect was dose dependent. In contrast, DALA treatment significantly decreased the frequency of aggressive actions in a dose-dependent manner. Similar significant effects of these two drugs were observed in the sexual behavior. These findings provide the first evidence for the role of opioid peptides in the reproductive behaviors in the bird and suggest an inhibitory action of opioid to evoke the behaviors.

Aggression↗
PubMed2001

Low-sexually performing rams but not male-oriented rams can be discriminated by cell size in the amygdala and preoptic area: a morphometric study.

Brain regions of male sheep behaviorally classified as high-sexually performing (n=10), low-sexually performing (n=8) or male-oriented (n=9) were examined to determine if differences in reproductive behavior were associated with differences in density or sizes of neurons. High-sexually performing rams actively mounted estrous ewes, low-sexually performing rams failed to mount or had long latencies to mounting estrous ewes, and male-oriented rams mounted other rams in preference to ewes in estrus. Cell densities and sizes were quantified in Nissl stained sections through the medial amygdala (meAMY), preoptic area (POA), bed nucleus of the stria terminalis (BNST), ventromedial hypothalamic nucleus (VMH), lateral geniculate nucleus (LG) and medial geniculate nucleus (MG). Multivariate discriminant analysis based on soma sizes within nuclei of known importance for reproductive behavior and/or gonadotropin release (meAMY, POA, BNST and VMH) discriminated (Wilks Lambda P<0.05) low-performing rams from high-performing and male-oriented rams, but did not discriminate (Wilks Lambda P=0.14) between high-performing and male-oriented rams. Cell size in the parvocellular and magnocellular layers of the LG along with cells of the MG, structures without a specific role in reproduction, did not discriminate any of the three behaviorally defined groups of rams (Wilks Lambda P=0.57). Density of cells present in structures important for the display of reproductive behavior (POA, meAMY, BNST) and/or gonadotropin release (POA, VMH) had no discriminating power nor did density of cells in structures important for the processing of visual (LG) or auditory (MG) stimuli. In conclusion, significant differences in sizes of cells located within nuclei that are specifically important for the display of male reproductive behavior were found in low-sexually performing rams compared to high-sexually performing and male-oriented rams. These differences may result from neuron development in utero or occur later as a consequence of endocrine factors or behavioral experience. Neuronal cell size is a critical variable that determines excitability to synaptic inputs because cell surface area varies exponentially with cell diameter. Relatively small differences in neuron diameter could relate to functionally important differences in neuronal excitability.

Amygdala↗
PubMed1976

Effects of interactions with older males on behavior and reproductive development in first-year male red-winged blackbirds Agelaius phoeniceus.

Male red-winged blackbirds Agelaius phoeniceus in their first year normally do not establish territories or breed. To investigate the possibility that interactions with older males might inhibit reproductive development of young males, we compared the behavior of first-year males in the presence and absence of older males. For three months during the first half of the breeding season, we studied mixed- and single-age groups of three males in standardized outdoor aviaries: two groups of three first-year males (FFF groups), two groups of one older and two first-year males (AFF groups), and one group of three older males (AAA group). In all groups one male established clear dominance, invariably the older male in AFF groups. The dominant male in FFF groups displaced subordinates less frequently than did the dominant older male in AFF groups early in the season, but equally frequently later. In May the largest testies weights of males in FFF groups were significantly lower than those of dominant older males in AFF groups. First-year males in the absence of direct interactions with older males can achieve levels of aggressive behavior comparable to those of a dominant older male in similar social environments but the seasonal development of their aggressive behavior occurs later and their testes in May are smaller than dominant adults'. This delay in the seasonal development of aggressive behavior in first-year males, independent of the immediate social environment, suggests that the age-dependent territoriality of males in this species is not strongly regulated by effects of older males on the development of younger males.

Age Factors↗
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↗
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↗
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↗
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↗