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PubMed1985

Effects of low stress during pregnancy on certain parameters of the offspring.

In recent years the effect of intense stress applied during pregnancy has been studied. In this work, we exposed the mother to low immobilization stress throughout the entire pregnancy. This treatment that increased the sexual capacity in males had no detectable effects on the reproductive behavior of females. A positive role of this phenomenon in nature is suggested, as the offspring of stressed mothers would be more capable of facing difficult and selective environments.

Animals↗
PubMed1988

Are pheromones their own reward?

Hamster vaginal discharge (HVD) contains a variety of intersexual pheromones which are powerful promoters of male reproductive behavior. Males avidly investigate and then consume HVD from females or from artificial sources. We measured the reward strength of HVD and other sapid substances with operant techniques. The highest fixed ratio at which males would bar press, the break point, varied with the level of water deprivation and the volume of water reward. Break points for sucrose rewards, in undeprived animals, were higher than for water and varied with concentration. Water, vanillin and HVD solutions were comparable reinforcers irrespective of deprivation level. Sexual experience did not increase bar pressing for HVD rewards. Moreover, naive animals could not be trained to bar press for HVD. These results contrast with other evidence that HVD is highly palatable and challenge the notion that the pheromones present in it are innately rewarding. However, this conclusion may be mitigated by constraints on learning which limit the utility of operant techniques to evaluate the reinforcing properties of HVD.

Animals↗
PubMed1988

Effects of uterine position on rate of sexual development in female Mongolian gerbils.

Examination of the rate of sexual maturation of 79 female gerbils from 32 Caesarean-delivered, foster-reared litters revealed that those females that, as fetuses, occupied uterine positions adjacent to one or two males (1M and 2M females) were less likely than those females occupying uterine positions not adjacent to males (0M females) to exhibit early vaginal opening. Our data further indicated that the uterine environment provided by late-maturing female gerbils biased their fetal daughters to themselves be late maturing to a greater extent than the daughters' uterine positions could explain. Daughters of late-maturing females in 1M and 2M uterine locations were more likely to be late-maturing than were daughters of early-maturing females in similar uterine locations. Because in female Mongolian gerbils age at vaginal opening is a powerful predictor of future reproductive strategy, the present results indicate that in female gerbils both prenatal maternal influence and uterine location are important determinants of future reproductive behaviors.

Animals↗
PubMed1993

Suppression of the lordosis reflex of female rats by efferents of the medial preoptic area.

In freely moving, estrogen- and progesterone-treated ovariectomized female rats, electrical stimulation of the medial preoptic area, which had been isolated dorsally from the septum by a horizontal knife cut (roof cut), caused immediate interruption of the lordosis reflex, a principal component of female reproductive behavior in this species. Neither the knife cut nor the stimulation affected their proceptive interactions with the males. Lordosis was interrupted in a graded manner in response to increased stimulus intensity, with a threshold at 30 microA. The optimal frequency was at 50-100 Hz. Lordosis was reinstated promptly by the termination of current application. The rapid time course distinguished the stimulation effect in the rats with the roof cut from that in the intact control animals, which was slow in its onset and recovery. In the sham-operated animals, an adjunct bilateral cut of the stria terminalis was sufficient to restore the rapid response as in the roof-cut animals. The roof-cut animals were sensitive to lower doses of estrogen than those without the knife cut; therefore, the preoptic area appears to be a separate entity from the septum in the inhibitory control of lordosis. The elimination of facilitatory neural components for this reflex, which enter the preoptic area dorsally via the stria terminalis, might be responsible for the prompt and exaggerated stimulation effect in the roof-cut animals.

Afferent Pathways↗
PubMed1995

Physiological substrates of mammalian monogamy: the prairie vole model.

Prairie voles (Microtus ochrogaster) are described here as a model system in which it is possible to examine, within the context of natural history, the proximate processes regulating the social and reproductive behaviors that characterize a monogamous social system. Neuropeptides, including oxytocin and vasopressin, and the adrenal glucocorticoid, corticosterone, have been implicated in the neural regulation of partner preferences, and in the male, vasopressin has been implicated in the induction of selective aggression toward strangers. We hypothesize here that interactions among oxytocin, vasopressin and glucocorticoids could provide substrates for dynamic changes in social and agonistic behaviors, including those required in the development and expression of monogamy. Results from research with voles suggest that the behaviors characteristics of monogamy, including social attachments and biparental care, may be modified by hormones during development and may be regulated by different mechanisms in males and females.

Animals↗
PubMed1991

Effects of conspecifics on feeding in Aplysia fasciata.

The presence of other Aplysia in the environment increases the time spent feeding. This finding is consistent with the hypothesis that a common arousal mechanism modulates feeding and reproductive behaviors. The arousal level is presumably increased by pheromones released by additional animals.

Animals↗
PubMed1994

Pubertal maturation is associated with an increase in the number of androgen receptor-immunoreactive cells in the brains of male ferrets.

Androgen receptor-immunoreactive (AR-IR) cells were identified in brains of male ferrets before and after the onset of pubertal maturation. There was a greater number of AR-IR cells after the onset of pubertal maturation in some, but not all, brain regions examined. Regions in which the number of AR-IR cells increased included the preoptic area and the amygdala, areas known to be involved in the control of male reproductive behaviors. The mechanisms responsible for the increase in AR-IR cells are unknown, but might be related to the higher circulating levels of testosterone that were present in the older animals. Testosterone may increase androgen receptor (AR) immunoreactivity both by concentrating already existing ARs within the nucleus and by stimulating de novo synthesis of receptor protein.

Aging↗
PubMed1994

Gonadotropin-releasing hormones in microdissected brain regions of an amphibian: concentration and anatomical distribution of immunoreactive mammalian GnRH and chicken GnRH II.

Mammalian and chicken II gonadotropin-releasing hormones (mGnRH, cGnRH II) were extracted from 350 microns diameter punches from brains of a urodele amphibian, Taricha granulosa, and measured by means of radioimmunoassay (RIA) with specific antisera. Measurable quantities of both peptides were found in the lateral pallium, the subpallium (along the course of the nervus terminalis), the preoptic area, habenula, optic tectum, infundibulum, paraventricular organ/posterior tubercle of the caudal diencephalon, medulla, and cerebrospinal fluid. Highest concentrations of both peptides were in the preoptic area and infundibulum, suggesting a role in gonadotropin release. In most extrahypothalamic regions, cGnRH II concentrations exceeded those of mGnRH, suggesting that cGnRH II may function as a neurotransmitter in many sites, perhaps to control reproductive behaviors. Results are largely consistent with immunocytochemical (ICC) analyses, except that RIA revealed small amounts of both peptides not found by ICC in some areas of the brain. Results from this microdissection/RIA study and prior ICC studies in amphibians support the conclusions that GnRH cell bodies in the terminal nerve and preoptic area, which project mainly to the median eminence and habenula, express mGnRH, and that GnRH cell bodies in the caudal diencephalon, which project widely throughout the CNS, express cGnRH II. Comparative data support the view that cGnRH II, and the neural systems in which it is expressed, evolved early in vertebrate phylogeny and have been highly conserved.

Animals↗
PubMed1995

Estrogen regulates preproenkephalin-A mRNA levels in the rat ventromedial nucleus: temporal and cellular aspects.

Numerous studies suggest that the ventromedial nucleus of the hypothalamus is a primary locus of control for reproductive behavior in the female rat. The display of lordosis behavior is estrogen dependent and its regulation appears to involve the activity of endogenous opioid circuits in the mediobasal hypothalamus and brainstem. Hypothalamic levels of preproenkephalin-A mRNA and the neuropeptide which it encodes, methionine-enkephalin, are dramatically up-regulated by estrogen. To characterize the temporal and cellular aspects of the effect of an acute exposure to estrogen on preproenkephalin-A mRNA levels in the ventromedial nucleus and arcuate nucleus of the hypothalamus, ovariectomized female rats were injected with 50 micrograms estradiol benzoate and used for quantitative in situ hybridization histochemistry of preproenkephalin-A mRNA. In the ventromedial nucleus, estrogen treatment caused a biphasic increase in the number of preproenkephalin-A mRNA cells. Maximal numbers of cells expressing preproenkephalin-A mRNA were observed at 1 and 48 h after estrogen injection. At 4 and 96 h after estrogen injection, the numbers of preproenkephalin-A mRNA cells were similar to that which was seen in the ovariectomized female. The induction of preproenkephalin-A mRNA expression in cells of the arcuate nucleus followed a similar pattern that peaked 48 h after exposure to estrogen. Levels of preproenkephalin-A mRNA per cell did not change in either nucleus as a function of estrogen treatment. Thus, acute estrogen treatment induces expression of preproenkephalin-A mRNA in populations of cells in the ventromedial hypothalamus and arcuate nucleus in which preproenkephalin-A mRNA expression is undetectable by in situ hybridization in the absence of circulating estrogen.

Animals↗
PubMed1996

Hormonal regulation of androgen receptor messenger RNA in the medial preoptic area of the male rat.

In the adult male rat, androgen and estrogen synergize in the regulation of male reproductive behaviors. To explore some of the molecular mechanisms underlying this synergism we examined the distribution and hormonal regulation of androgen receptor (AR) and estrogen receptor (ER) mRNAs in the medial preoptic area (MPOA) and bed nucleus of the stria terminalis (BST) of the adult male rat. Using in situ hybridization, AR and ER mRNAs were found to be distributed in overlapping but unique patterns. The highest density of AR mRNA was found in the central part of the medial preoptic n. and the principal n. of the BST. Gonadectomy (GDX) of adult male rats caused an increase in hybridization density in both brain areas after 4 days followed by a decrease after 2 months. In contrast, ER mRNA was increased following GDX and remained high regardless of length of time. Treatment of adult GDX'd males with dihydrotestosterone (DHT) reversed the effects of GDX on AR mRNA at both the short and long-term castrate but had no effect on ER mRNA in both the MPOA and BST. Estrogen treatment increased AR mRNA in the long-term castrate only and decreased ER mRNA in both long- and short-term castrates. Immunocytochemical detection of AR revealed a similar distribution to AR mRNA; however, AR immunoreactivity was reduced in the MPOA and BST after both short- and long-term GDX. In vitro [3H]DHT binding in cytosols of the preoptic area showed appreciable binding but there was no effect of length of time following GDX. These data show that the pattern of regulation of AR mRNA is unique to this receptor type and does not follow the pattern of regulation of the ER mRNA. Furthermore, although the distribution of AR mRNA and AR protein coincide within the MPOA, changes in mRNA levels as a result of castration or hormone treatment do not result in corresponding changes in binding. This mismatch between mRNA and binding suggests a complex regulation of AR beyond simply changes in transcription.

Animals↗
PubMed1994

Biological actions of cholecystokinin.

Cholecystokinin (CCK) has emerged as an important mammalian neuropeptide, localized in peripheral organs and in the central nervous system. This review presents an overview of the molecular aspects of CCK peptides and CCK receptors, the anatomical distribution of CCK, the neurophysiological actions of CCK, release of CCK and effects of CCK on release of other neurotransmitters, and the actions of CCK on digestion, feeding, cardiovascular function, respiratory function, neurotoxicity and seizures, cancer cell proliferation, analgesia, sleep, sexual and reproductive behaviors, memory, anxiety, and dopamine-mediated exploratory and rewarded behaviors. Human clinical studies of CCK in feeding disorders and panic disorders are described. New findings are presented on potent, nonpeptide CCK antagonists, selective for the two CCK receptor subtypes, which demonstrate that endogenous CCK has biologically important effects on physiology and behavior.

Amino Acid Sequence↗
PubMed1989

Women, household and health in Latin America.

Although recent studies have identified some of the links in Latin America between uneven capitalist economic development and health, the impact of development on either the health of women or on household health is still largely unknown. This account identifies several areas of needed research. It focuses on how changing women's roles and patterns of domestic production affect women's reproductive behavior, and the consequences of these changes for the health of women and other members of their households.

Family↗
PubMed1995

Factors associated with pregnancy and pregnancy resolution in HIV seropositive women.

This study examines factors associated with pregnancy and pregnancy resolution among 238 HIV-infected women, 55 of whom experienced a recent pregnancy since learning of their HIV positive serostatus. Results suggest the importance of psychosocial and cultural factors, particularly those involving the primary sex partner, to reproductive decision-making in HIV-infected women. They also indicate a consistency of reproductive behavior before and after HIV infection, suggesting that the infection itself does not significantly alter existing childbearing trends. Biomedical considerations relating to the mother's health status and the risk of transmission to the child have a greater impact on decisions surrounding pregnancy resolution than they do on the probability of becoming pregnant.

Abortion, Induced↗
PubMed1986

Auditory pathways to the hypothalamus in ranid frogs.

Three multisynaptic pathways from the midbrain auditory center (torus semicircularis) of the bullfrog, Rana catesbeiana, to the infundibular hypothalamus were found using the axonal tracer wheat germ agglutinin-horseradish peroxidase. Toral neurons project to the secondary visceral nucleus of the isthmus and to the central and anterior thalamic nuclei of the dorsal thalamus. All 3 of these nuclei project to the infundibular hypothalamus. These findings indicate multiple connections between two centers presumed important for reproductive behavior in frogs, a midbrain sensory region processing acoustic communication signals and a hypothalamic endocrine control area regulating gonadotropin and gonadal steroid secretion.

Animals↗
PubMed1993

Evidence of a direct projection of the vomeronasal organ to the medial preoptic nucleus and hypothalamus.

In rodents the vomeronasal system plays an important role in modulating the hypothalamic control of gonadotropin secretion. It is accepted that the anatomical pathways by which the vomeronasal organ influences the neuroendocrine aspects of the reproductive behavior involves a polysynaptic system, including the accessory olfactory bulb, the 'vomeronasal amygdala', the bed nucleus of the stria terminalis and medial preoptic and ventromedial hypothalamic nuclei. We found that 72 h after unilateral transection of the vomeronasal nerves of an ipsilateral orthograde degeneration is seen in the neuropil of the medial preoptic, ventromedial, and arcuate hypothalamic nuclei. This represents an anatomical evidence of a monosynaptic link between the vomeronasal neuroepithelium and the medial preoptic nucleus, and hypothalamus.

Animals↗
PubMed1990

Projections of ventromedial hypothalamic neurons to the midbrain central gray: an ultrastructural study.

Ventromedial hypothalamic projections to the midbrain central gray may be involved in the mediation of female reproductive behavior. In order to demonstrate and examine projections of the ventromedial nucleus in the midbrain central gray, in the rat, electrolytic lesions were placed in the ventromedial nucleus and the midbrain central gray was examined for ultrastructural signs of degeneration at various intervals, i.e. 27.5 h and two, four, six and eight days following the lesions. The fine structure of the midbrain central gray of unlesioned animals was also examined to characterize its normal morphology and to establish a baseline with which to compare the effects of the lesion. In unlesioned animals, the neuropil of midbrain central gray contained several synaptic types, with axodendritic synapses appearing to be the most predominant. Dendrites contained well-preserved microtubules. Synaptic endings contained many clear, round vesicles and some contained dense-cored vesicles as well. Neuropil synapses were both asymmetric and symmetric. Cell bodies were characterized by light cytoplasm and had asymmetric and symmetric synapses on their surface. Following electrolytic lesions in the ventromedial nucleus, various types of degenerative patterns were seen in the midbrain central gray, including electron-dense, flocculent, watery, and pinocytotic degeneration. Specific characteristics of degeneration included shrunken, dense axons and endings, clumped synaptic vesicles, abnormally large, dark mitochondria, membranous sacs of various sizes, swollen endings with reduced numbers of synaptic vesicles, and endings and processes containing large numbers of coated vesicles. Some of these signs were already evident at 27.5 h following the lesion. In addition, degenerating postsynaptic processes and cell bodies were seen in the midbrain central gray. At 27.5 h survival time, degenerating dendritic processes often appeared swollen, devoid of microtubules, and contained enlarged mitochondria. At longer survival times neuronal degeneration was observed in the midbrain central gray, characterized by electron-dense cell bodies and pycnotic nuclei. Both degenerating pre- and postsynaptic elements appeared to be engulfed by glial processes. Control lesions in non-hypothalamic regions which project to the midbrain central gray, i.e. nucleus gigantocellularis and pontine reticular formation and in a non-projecting region, i.e. parietal cortex, were performed.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1993

Excitatory and inhibitory synaptic processing in the accessory olfactory system of the female rat.

The accessory olfactory system constitutes a sensory system specifically involved in regulating neuroendocrine function and reproductive behavior. The chemosensitive structure of this system, the vomeronasal organ, exclusively innervates the accessory olfactory bulb, which in turn projects via mono- or disynaptic pathways to a limited number of regions implicated in endocrine and sexual function, including the amygdala and hypothalamus. The present study investigated synaptic processing between the different levels of this sensory system, with particular focus on the input from the accessory olfactory bulb to the medial amygdala and the reciprocal connections between the medial amygdala and the ventromedial hypothalamus. Extracellular single-unit recordings were obtained from medial amygdala neurons in anesthetized female rats to study the synaptic responses elicited by stimulation of the olfactory bulb and hypothalamus. Locally applied agonists and antagonists of amino acid neurotransmitters were tested for their ability to mimic and block these synaptic responses in an attempt to identify the neurotransmitters involved in the stimulated pathways. Electrical stimulation of the accessory olfactory bulb induced orthodromic responses in 88% of 288 medial amygdala neurons, with 67% showing orthodromic inhibition and 21% showing excitation as the shortest-latency response. Many cells displayed multiphasic responses with both orthodromic excitation and inhibition. In separate experiments, main olfactory bulb stimulation also produced excitatory (39%) or inhibitory (50%) orthodromic responses in medial amygdala neurons (n = 105), but the latency and distribution of responses were significantly different than with accessory olfactory bulb stimulation. Stimulation of the ventromedial hypothalamus also had prominent excitatory (29%) or inhibitory (59%) orthodromic actions on the majority of amygdala neurons. Out of 288 cells tested with both accessory olfactory bulb and ventromedial hypothalamus stimulation, 79% were orthodromically responsive to both areas, whereas only 3% responded to neither area. Fourteen (6%) medial amygdala neurons were antidromically activated from the ventromedial hypothalamus, and 11 of these 14 cells were simultaneously orthodromically responsive to accessory olfactory bulb stimulation, indicating that the accessory olfactory bulb can influence medial amygdala neurons that project directly to the hypothalamus. Iontophoretic application of drugs to the medial amygdala revealed that glutamate and GABA consistently mimicked the orthodromic excitatory and inhibitory responses, respectively, from both the accessory olfactory bulb and ventromedial hypothalamus. In some cases, ejection of bicuculline could block or reverse excitation of the orthodromic inhibitory responses, whereas kynurenic acid could eliminate the orthodromic excitation, indicating that excitatory and inhibitory amino acid transmitters are at least partially involved in these pathways.(ABSTRACT TRUNCATED AT 400 WORDS)

Amygdala↗
PubMed1994

Projections of the suprachiasmatic nuclei, subparaventricular zone and retrochiasmatic area in the golden hamster.

The patterns of projections from the hamster suprachiasmatic nucleus, retrochiasmatic area and subpraventricular hypothalamic zone were examined using anterograde tracing with the plant lectin, Phaseolus vulgaris leucoagglutinin. Suprachiasmatic nucleus efferents comprise four major fiber groups: (i) an anterior projection to the ventral lateral septum, the bed nucleus of the stria terminalis and anterior paraventricular thalmus; (ii) a periventricular hypothalamic projection extending from the preoptic region to the premammillary area; (iii) a lateral thalamic projection to the intergeniculate leaflet and ventral lateral geniculate; and (iv) a posterior projection to the posterior paraventricular thalamus, precommissural nucleus and olivary pretectal nucleus. The retrochiasmatic area showed a similar projection pattern with several major exceptions. There are projections to endopiriform cortex, fundus striati, ventral pallidum, horizontal limb of the nucleus of the diagonal band and three separate routes to the amygdala. There are also projections laterally with fibers of the supraoptic commissures, which enter the superior thalamic radiation and innervate the caudal dorsomedial thalamic nuclei. Other fibers traveling with the commissures terminate in the ventral zona incerta. The subparaventricular zone projects to most targets of the suprachiasmatic nucleus, but not to the intergeniculate leaflet. There is a substantial input to both the subparaventricular zone and retrochiasmatic area from the suprachiasmatic nucleus, but little apparent reciprocity. There is extensive overlap of suprachiasmatic nuclei and retrochiasmatic efferents, and between retrochiasmatic and known medial amygdaloid efferents. The anatomical information is discussed in the context of circadian rhythm regulation, photoperiodism and chemosensory pathways controlling male hamster reproductive behavior.

Animals↗