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PubMed1999

Thyroid hormone coadministration inhibits the estrogen-stimulated elevation of preproenkephalin mRNA in female rat hypothalamic neurons.

Expression of the enkephalin gene in ventromedial hypothalamus (VMH) of the female rat has been correlated with the performance of lordosis behavior. By antisense DNA evidence, it has been drawn into a causal role as well. Here, we explored whether, parallel to earlier molecular and behavioral results, thyroid hormone coadministration could disrupt the estrogenic induction of preproenkephalin (PPE) mRNA. As expected, estradiol benzoate treatment to ovariectomized rats led to a large and significant increase in PPE gene expression in the VMH. This increase was inhibited by coadministration of thyroid hormone. The thyroid hormone interference in PPE gene expression was specific to the VMH, as there were no significant effects in the central nucleus of the amygdala or in the caudate/putamen. These in situ hybridization histochemical results form a direct parallel both to previous transcriptional measurements and to reproductive behavior assays in which thyroid hormones were able to oppose estrogenic facilitation. Previous evidence supports the notion of competitive DNA binding and protein/protein interactions providing mechanisms for nuclear thyroid hormone receptors to affect estrogen receptor function, but other, additional mechanisms cannot be ruled out. To date, both oxytocin and PPE gene expression represent potential hypothalamic systems by which thyroid hormones could interfere with estrogen-stimulated female rat reproductive behavior.

Amygdala↗

PubMed2005

[Socioeconomic and contextual determinants of reproductive activity among adolescent women in Colombia].

OBJECTIVE: To contribute to a better understanding of the problems of pregnancy among adolescent women, including proximate and socioeconomic determining factors, in two large, culturally different cities in Colombia: Santa Fe de Bogotá and Cali. METHODS: This longitudinal study combined quantitative and qualitative research methods, using information generated by a survey of adolescents conducted in 2003. The survey included 550 adolescents in Bogotá and 550 adolescents in Cali, from all socioeconomic strata. To analyze the determinants, discrete-time proportional hazards models were used. For the qualitative study, 72 in-depth interviews and four focus groups were done. With the information organized by subjects and categories that were defined in relation to the purposes of the study, categories were identified that arose from the patterns and recurrences in the data, in order to see sociocultural trends by sex, stratum, and city. RESULTS: The patterns of sexual activity, union (married or unmarried relationship), and maternity differ considerably among the socioeconomic strata, in both of the cities. The adolescent women in the low stratum begin having sexual relations, form unions, and become mothers earlier in life and with greater frequency than do adolescent women in the medium or high strata. The main determinant of the reproductive behavior of adolescent women is the set of contextual and socioeconomic factors in the home, mainly the family context (environment and supervision) and the educational climate (the average number of years of formal education of the family members over the age of 15). CONCLUSIONS: Sex education has been provided in the schools in Colombia since 1993, but our results clearly indicate that it has had only a limited impact on the reproductive behavior of adolescent women.

Adolescent↗

PubMed1999

Sexual dimorphisms in avian and reptilian courtship: two systems that do not play by mammalian rules.

Sexual dimorphisms in the central nervous system exist in numerous vertebrate species, and in many cases these structural differences between males and females parallel differences in the display of reproductive behaviors. Often both the behavioral and anatomical differences are controlled by exposure to gonadal steroid hormones, either during ontogeny or in adulthood. This article reviews some of the evidence supporting the hypothesis that in mammals, testosterone or its metabolites regulate the structure and function of neural and muscle systems involved in the control of masculine sexual behaviors. It then describes data suggesting that the mechanisms regulating sexually dimorphic courtship systems in zebra finches and green anole lizards are not completely parallel to the mammalian systems. Finally, some directions for future study are suggested, with the hope that they will stimulate thought about the nature of comparisons made across vertebrate models when investigators are attempting to determine both which morphological sex differences are important to the control of the reproductive behaviors, and which mechanisms regulating both structure and function are widely employed or are unique.

Animals↗

PubMedDate not supplied

[A comparative socio-demographic study of nuptiality in two states: Aguascalientes and Veracruz].

"In this article, nuptiality is studied as a demographic and social phenomenon.... The study focuses on two states of [Mexico]: Aguascalientes and Veracruz, where the author analyzes the formation of couples, the social norms which determine marriage behavior patterns, and the interaction between marriage and reproductive behavior patterns....[The study] includes a description of the characteristics and patterns of unions in the two regions based on data from the 1982 'Encuesta Nacional Demografica' (National Demographic Survey) and on published studies on the subject." (SUMMARY IN ENG)

Americas↗

PubMed1975

Fertility and family planning in Thailand: results from two rounds of a national study.

The Longitudinal Study of Social, Economic, and Demographic Change was undertaken during the late 1960s to provide detailed national information on behavior and attitudes related to fertility and family planning in Thailand. Results from the second round of the study indicate that the practice of family planning increased substantially in both rural and urban areas during the three-year interval between the two rounds. During this period, marital fertility registered a decline in the urban areas. This was a result of a small rise in fertility among Bangkok-Thonburi women combined with a sharp decline in fertility among provincial urban women. Because the National Family Planning Program was officially begun at the time of the first round, its role in the increase in contraceptive use is examined. Although the study shows that the desired number of children is substantially below the actual number of children Thai womenhave by the end of their reproductive years, the desired number of children is still well above the number usually considered ideal in developed countries. Nonetheless, changes in reproductive behavior appear to reflect the impact of modernization on Thai society. In urban areas, marital fertility is only moderately high and a substantial proportion of couples practice family planning. Of particular importance over the remainder of the decade will be the reproductive behavior of rural women, who constitute an extremely high proportion of the Thai female population.

Adolescent↗

PubMed1989

Expression and estrogen regulation of progesterone receptor mRNA in neurons of the mediobasal hypothalamus: an in situ hybridization study.

Diverse effects of steroid hormones on different tissues result from the tissue-specific regulation of target gene expression by steroid hormone receptors. These receptors belong to a family of transacting factors that regulate transcriptional activation of target genes by binding to DNA recognition sequences located in the 5'-flanking region of the target gene. In the brain, receptors for the gonadal steroid hormones estrogen (E) and progesterone (P) are present in discrete neuronal populations. These steroid hormone receptor-containing neurons mediate the effects of the gonadal steroids on a number of neural processes, including reproductive behavior. Using in situ hybridization we have found progesterone receptor (PR) mRNA-containing neurons present in specific hypothalamic nuclei and in the amygdala. E regulates PR mRNA levels in specific neuronal cell groups which express both ER and PR (in basomedial hypothalamus), but not in others (medial amygdala). The E-induced increase in P-responsive neurons in ventromedial hypothalamus can account for the permissive influence of E on P-facilitated reproductive behavior. This is the first demonstration that synthesis of a transcription factor (PR) can be related to a mammalian behavior.

Animals↗

PubMedDate not supplied

Comparative effects of maternal prenatal and postnatal exposures to astemizole on reproductive parameters of rats.

The prenatal and postnatal effects of administration of a nonsedative antihistamine H1, astemizole (ATZ), were compared. ATZ (10 mg/kg) was injected daily into female Wistar rats throughout pregnancy (prenatal treatment) or during the first 6 days of lactation (postnatal treatment). Neither treatment modified dam body weight. Prenatal exposure reduced offspring body weight and lead to a latter expression of the vaginal opening of female offspring. In addition, a long-term disruption of male reproductive behavior was observed, while female sexual behavior was not modified. The sexual activity index and the intromission frequency were increased in prenatally treated animals. Testes wet weight was reduced, but no modifications were detected in vas deferens or seminal vesicles. Postnatal treatment did not alter offspring body weight, open-field activity, sexual behavior and organ weight as well as did not delay testes descent but reduced the time until vaginal opening. Hypothalamic serotonin (5-HT), dopamine (DA) and noradrenaline (NA) as well as DA and NA metabolites were not modified by both prenatal and postnatal treatments. Increased striatal 3,4-dihydroxyphenylacetic acid (DOPAC) levels were observed after prenatal and postnatal treatments, while only postnatal 5-HT levels were increased. We propose that the present results indicate that prenatal ATZ exposure can have long-lasting organizational effects on reproductive behavior of male rats, while postnatal exposure to this drug did not alter mating behavior. In relation to female rats, prenatal and postnatal exposures to ATZ accelerated puberty but did not alter sexual behavior. Neurochemical data show that both treatments increased striatal dopaminergic system activity, suggesting a central ATZ effect after perinatal exposure.

Animals↗

PubMed1994

Arginine vasotocin facilitation of advertisement calling and call phonotaxis in bullfrogs.

Although the neuropeptide arginine vasotocin (AVT) is found in several auditory and vocalization regions of the bullfrog (Rana catesbeiana) brain, its functions in these areas are unknown. We examined the effects of AVT injection on two auditory-evoked reproductive behaviors: advertisement calling in male bullfrogs and call phonotaxis in female bullfrogs. AVT (500 micrograms; intraperitoneal) significantly increased advertisement call frequency and decreased calling latency in male bullfrogs, compared to saline injection. This dose of AVT also significantly decreased the time required for female bullfrogs to reach a call source as well as the latency of females to leave the starting position during call playback. In both males and females, these effects were significant at 0.5 hr and persisted until at least 2 hr after injection. AVT thus facilitated display of two sexually-dimorphic reproductive behaviors in bullfrogs. These effects may be due to direct effects of AVT on auditory processing regions in the bullfrog brain.

Animals↗

PubMedDate not supplied

Maternal age as a factor in determining the reproductive and behavioral outcome of rats prenatally exposed to ethanol.

Nulliparous Long-Evans rats were bred at one of four different ages and assigned to one of three treatment groups within each age condition. Maternal ages were 9, 18, 32, and 36 weeks. Treatment groups were ethanol (E), administered by gavage as 8 g/kg in two divided doses on days 10-14 of gestation, pair-fed (PF) controls, administered as an isocaloric sucrose solution by gavage on days 10-14 of gestation, and ad lib fed controls (C). All offspring were surrogate fostered shortly after delivery to untreated recently parturient dams. Litter sizes were standardized to 8 on the day of birth. Offspring were assessed longitudinally for growth, mortality, and behavior (olfaction, locomotor activity, maze learning, avoidance acquisition and startle). Approximately 85% of the 36 week old dams did not produce viable litters. In the remaining maternal age conditions, ethanol delayed offspring olfactory orientation and increased locomotor activity, the latter dissipating after 50-60 days of age. These ethanol-related effects occurred independent of maternal age condition. Maternal age, independent of ethanol, was a factor which reduced litter size and offspring weight up to 50 days, but produced few effects on behavior. The combination of maternal age and prenatal ethanol interacted to increase pregnancy loss (oldest maternal age), reduce offspring weight up to day 99 (oldest and middle maternal age), alter olfactory orientation performance (oldest and middle maternal age), reverse the typical ethanol-induced increase in activity for males in the figure-8 test (oldest maternal age group), shift the pattern of open-field activity, and change errors in a complex water maze. Not all of these interactions turned out to be specific to the ethanol X old maternal age condition. Several of the interactions occurred in both the old and middle maternal age conditions. The only effect of old maternal age that interacted strongly with ethanol was in their combined effects on reproduction. Here the combination of the two factors increased maternal mortality, the number of early pregnancy losses, and the number of litters where all members were dead or resorbed. It was concluded that short-term prenatal ethanol combined with advanced maternal age produces additive interactions on pregnancy success without affecting longer-term outcomes, while young maternal age showed no clear detrimental effects compared to the middle maternal age reference group.

Aging↗

PubMed2002

Acute fasting decreases sexual receptivity and neural estrogen receptor-alpha in female rats.

Acute food deprivation or chronic food restriction suppresses reproduction in female mammals. Although a link between undernutrition and ovarian function is well established in rats, a similar link with reproductive behavior in this species is yet to be described. Therefore, we compared the display of estrous behaviors induced by exogenous steroid hormone treatment in ovariectomized fed and fasted rats. In addition, estrogen receptor-alpha immunoreactivity (ERIR) was measured in fed and fasted animals to determine whether changes in behavior were associated with changes in the number of detectable ERIR-containing cells in several brain regions. Fasting for 74 h decreased lordosis quotients (LQ) and lordosis ratings (LR) in ovariectomized, steroid-primed rats. The number of detectable ERIR cells decreased after a 74-h fast in the mid-region of the arcuate (ARC), paraventricular (PVN) and ventromedial nuclei of the hypothalamus (VMH) and the ventral bed nucleus of the stria terminalis (BST) but did not change in a number of other areas examined. Taken together, these data demonstrate that, similar to the effect on the reproductive-endocrine axis, food deprivation for 74 h suppresses steroid-induced display of lordosis in adult, female rats. Furthermore, this suppression in sexual receptivity is associated with a decrease in ERIR in a number of areas, including the VMH, a region of the hypothalamus known to be critical for the display of reproductive behaviors in female rats.

Animals↗

PubMed1995

Oxytocin and female sexuality.

A search of the literature has been prepared to determine how oxytocin may affect sexual and reproductive in women. Many animal studies suggest that oxytocin induces a variety of reproductive behaviors, including grooming, sexual arousal, orgasm, gamete transport, nesting, birthing, and specific maternal behaviors such as breast-feeding and bonding between mother and infant. These actions are apparently facilitated by the 'priming' effect on certain cells by sex and steroid hormones - as the brief case report would also suggest. However, no adequate double-blind trial has confirmed the observations from this report in women. Only animal studies have been performed, albeit over a wide range of species. A variety of other causes and effects of sexual interest and arousal relating to oxytocin are considered, including some of those in males. More research is needed to clarify the role of oxytocin in human reproductive behaviors, including its potential 'aphrodisiac' or prosexual effect in women in the presence of the sex-steroid hormones.

Female↗

PubMed1994

Differential fertility as a mechanism maintaining balanced polymorphisms in Sardinia.

Women's fertility, gathered from the 1961 Italian population census, and estimates of heterozygote frequencies for thalassemia and G6PD deficiency (Siniscalco et al. 1961, 1966) in 52 Sardinian villages were examined to study at the population level the mechanisms that have maintained the stability of these polymorphisms over long periods. Sardinian villages were classified according to low or high frequency of heterozygotes, and the reproductive behavior of the women living in these areas was analyzed. A high mean number of children per woman and a low percentage of women without children with a high heterozygote frequency was demonstrated. The observed differential fertility and sterility were interpreted as being the result of different numeric ratios within each area between normal homozygous and heterozygous women, who were less and more resistant, respectively, to malarial infection, according to Haldane's theory. The effect of differing degrees of malaria on fertility rates has been demonstrated previously (Zei et al. 1990). To account for the effect of the genetic and epidemiological composition of an area on reproductive behavior, we classified data on women's fertility and sterility by heterozygote frequency level and malarial morbidity level. A combined and direct effect of inherited and acquired immunities on fertility and sterility rates was shown. The level of endemicity in an area may contribute to decreasing or increasing fitness, which is already influenced by the stable balanced polymorphisms.

Adult↗

PubMed1991

Endogenous opioid-immunoreactive neurons of the ventromedial hypothalamic nucleus concentrate estrogen in male and female rats.

Estrogen stimulates expression of proenkephalin mRNA in neurons of the hypothalamic ventromedial nucleus, and evidence is accumulating that synaptic release of one of the peptide end products, met-enkephalin, influences events that regulate reproductive behavior. To address the question of whether estrogen acts directly on neurons that synthesize met-enkephalin or indirectly through a separate neuronal population, we combined estrogen autoradiography with endogenous opioid peptide (EOP) immunohistochemistry. In agreement with previous studies, the ventrolateral subdivision of the hypothalamic ventromedial nucleus was densely packed with EOP-immunoreactive cells. In males, 48% of the estrogen-concentrating cells of the ventrolateral subdivision of the hypothalamic ventromedial nucleus contained EOP, and, in females, 27% of the estrogen-concentrating cells contained EOP. These findings indicate that estrogen acts directly on neurons that express EOP and suggest a mechanism that underlies sexually differentiated reproductive behavior.

Animals↗

PubMedDate not supplied

The influence of environment, sex, and innate timing mechanisms on body temperature patterns of free-ranging black-tailed prairie dogs (Cynomys ludovicianus).

Mechanisms that influence body temperature patterns in black-tailed prairie dogs are not well understood. Previous research on both free-ranging and laboratory populations of black-tailed prairie dogs (Cynomys ludovicianus) has suggested that reductions in ambient temperature and food and water deprivation are the primary factors that stimulate torpor in this species. In other species, however, torpor has been shown to be influenced by a multitude of factors, including innate circadian and circannual timing mechanisms, energy status, and reproductive behaviors. Our objective was to clarify the influence of weather, sex, and intrinsic timing mechanisms on the body temperature patterns of free-ranging black-tailed prairie dogs. We monitored body temperatures of eight adult (>1 yr) prairie dogs from November 1999 to June 2000. Prairie dogs showed distinct daily and seasonal body temperature patterns, which reflected changes in ambient temperatures that occurred during these periods. These patterns of daily and seasonal heterothermy suggest that body temperature patterns of black-tailed prairie dogs may be driven by an innate timing mechanism. All prairie dogs entered torpor intermittently throughout winter and spring. Torpor bouts appeared to be influenced by precipitation and reductions in ambient temperature. Our results also suggest that reproductive behaviors and circadian timing may influence torpor in this species.

Animals↗

PubMed2003

Gonadotropin-releasing hormones modulate electrical activity of vasotocin and isotocin neurons in the brain of rainbow trout.

Gonadotropin-releasing hormone (GnRH) is widely distributed in the vertebrate brains; however, its significance in the brain function is poorly understood. Both GnRH and vasopressin-family hormones are involved in control of reproductive behavior. Anatomical evidence indicated the possible action of GnRH on classical neurosecretory neurons. In the present study, we examined whether GnRH modulates electrical activity of vasotocin (VT) and isotocin (IT) neurons in the brain of rainbow trout (Oncorhynchus mykiss). Two forms of GnRH, salmon GnRH and chicken GnRH II, are present in the rainbow trout brain, and their fibers are localized in the close vicinity of VT and IT neurons. Applications of both GnRH forms elevated the frequency of cell-type-specific synchronous Ca(2+) pulses in VT and IT neurons that are blocked by a GnRH-receptor antagonist. Our results showed facilitatory actions of GnRHs on VT and IT neurons, suggesting that GnRH neurons modulate classical neurosecretory neurons to control reproductive behavior.

Action Potentials↗

PubMed1984

Alteration by estrogen of the nucleoli in nerve cells of the rat hypothalamus.

Estrogen is accumulated from the blood by nerve cells in the ventromedial nucleus of the hypothalamus and can facilitate female reproductive behavior by acting on this region of the brain. This cell group was examined in ovariectomized female rats, given estrogen or control treatment, by use of light and electron microscopy. A significantly greater portion of the nerve cells in the estrogen-treated animals had protuberances on their nucleolar surfaces, apparent under the light microscope. The fine structure of such protuberances included dense, aggregated material, which is shown to contain DNA by the sodium tungstate staining technique. Because increased numbers of such protuberances were found in nuclei of cells of the experimental group where previous studies demonstrated a significant increase in ultrastructural signs of biosynthetic activity, they may be associated with increased RNA synthesis. Thus, they could indicate, ultrastructurally, increased synthetic rates for RNA in nerve cells through which estrogen promotes reproductive behavior.

Animals↗

PubMed2003

Females prefer carotenoid colored males as mates in the pentamorphic livebearing fish, Poecilia parae.

The first results of female preference and chosen male mating success in a new model organism, the pentamorphic livebearing fish, Poecilia parae, are presented. Poecilia parae is a relative of the guppy, P. reticulata, and is assumed to have similar reproductive behavior. We tested the hypothesis that P. parae females, like female guppies, prefer carotenoid colored males as mates. Here we show that the time a female spent with males was significantly greater for carotenoid coloration in red and yellow melanzona, but time with these two morphs did not differ. The preferred red and yellow males mated significantly more often with their choosing females than did the non-preferred blue and parae males. The few blue melanzona and parae males that mated did so without performing courtship displays. Some females mated with all phenotypes including immaculata males during open group trials. Female P. parae clearly preferred males with carotenoid coloration, thereby corroborating the hypothesis. Alternative male mating tactics by blue melanzona, parae, and immaculata morphs and promiscuous mating by females also resembled features of reproductive behaviors exhibited by guppies.

Animals↗

PubMed2006

Stimulation of cyclic AMP formation and nerve electrical activity by octopamine in the terminal abdominal ganglion of the female gypsy moth Lymantria dispar.

The biogenic amine octopamine is known to be present in the abdominal ganglia of some insects, but the expression of functional octopamine receptors in these neuronal structures has not yet been characterized. In the present study, we describe the presence in the female gypsy moth terminal abdominal ganglion (TAG), a key structure in the control of the insect reproductive behavior, of an octopamine receptor coupled to stimulation of adenylyl cyclase through the GTP-binding protein G(s). The rank order of potency of different antagonists, which discriminate between the different classes of octopamine receptors, indicated the involvement of the neuronal type 3 receptor. The octopamine-stimulated adenylyl cyclase activity was inhibited by Ca(2+) in the low micromolar range and by activation of either protein kinase A or protein kinase C. In the isolated TAG, bath application of octopamine caused an increase of the spontaneous bursting activity of the emerging nerve of the 5th pair (V), whereas the antagonist mianserin reduced the nerve spiking activity and blocked the stimulatory effect of octopamine. These data demonstrate that the gypsy moth TAG expresses functional octopamine receptors, which may participate in the neuronal control of the insect reproductive behavior.

Abdomen↗