Changes in rhythmicity of ambulatory and drinking activities in immature female rats

Adult female rats showed increase in ambulatory activity and marked decrease in drinking behavior at early dark period (18:00-24:00) of proestrus stage before ovulation. In this study, we observed the changes in patterns of ambulatory and drinking activities of immature rats associated with estrous cycle during growing period. Immature female rats of the Wistar-Imamichi strain were used, and both behavioral activities were measured continuously, using Gundai type Ambulodrinkometer. From these observations, it was found that the typical patterns of ambulatory and drinking activities which were observed in adult female rats appeared at the sixth (51-60 days old) and the third (39-49 days old) estrous cycle, respectively.     

Effects of D2 receptor agonist and antagonist on behavior of intact and ovariectomized rats

The involvement of D2 dopaminergic receptors in behavioral responses during ovary cycle was assessed in adult intact female rats and ovariectomized (OVX) female rats. Quinperole (0.1 mg/kg), D2 receptor agonist and sulpiride (10.0 mg/kg), D2 receptor antagonist were injected chronically to adult intact and ovariectomized (OVX) female rats either separately or in combination with 17beta-estradiol (0.5 microg) within 14 days. Behavior of these animals was assessed in the "open field" test, whereas passive avoidance performance served as a model of learning. In intact rats, the passive avoidance performance was observed only in metestrous and diestrous. Chronic quinperole administration to intact females resulted in the appearance of the passive avoidance performance in proestrous and estrous, as distinct from the control animals. The passive avoidance performance was not reproduced in OVX rats. Quinperole per se or in combination with 17beta-estradiol completely restored the passive avoidance performance in OVX rats. Moreover, quinperole or sulpiride administration to OVX rats increased horizontal locomotor activity, exploratory behavior, and grooming behavior.     

Effect of consumption of sucrose and saccharin on passive avoidance learning in female Wistar rats

Influence of consumption of 32% sucrose or 0.1% saccharin solutions on passive avoidance acquisition in female Wistar rats was studied at different stages of estrous cycle. Under conditions of weak electrical shock, rats of the control and saccharin groups showed no acquisition at any stage of estrous cycle. Under the same conditions females of the sucrose group acquired the avoidance behavior if trained on the first day of diestrous and metestrous but not proestrous and estrous. The stage of estrous cycle on the second day did not influence the latency during testing session.     

Aggression in the female golden hamster: effects of reproductive state and social isolation

To gain information on possible hormonal correlates, the aggressive behavior of intact female hamsters towards males was observed at various times during the estrous cycle, pseudopregnancy, pregnancy, and lactation. For methodological information, estrous cycle females also were tested after varying periods of social isolation. It was found that pregnant and especially lactating hamsters were more aggressive than pseudopregnant or estrous cycling females. Comparisons of days within each reproductive condition showed that aggression tended to be higher on certain days: the day preceding behavioral estrus of the estrous cycle, Day 10 of pregnancy, and the first 5 days of lactation. Except for pseudopregnancy, sexual behavior unaccompanied by aggression occurred at some time during all reproductive conditions, and both sexual behavior and aggression were found to occur together on Day 10 of pregnancy and Day 1 of lactation. The changes in aggressive behavior associated with reproductive states were attributed to increased male interest, inhibition by ovarian hormones, and facilitation by prolactin. Increasing periods of social isolation also were found to be associated with increased aggression. It was suggested that this effect, too. might have been due to increased prolactin levels.     

Dynamic change in charge heterogeneity of pituitary FSH throughout the estrous cycle in female rats

Anterior pituitaries were removed from female rats at various stages during the estrous cycle and FSH was fractionated by isoelectric focusing (IEF). Fourteen FSH components were observed during the estrous cycle and twelve of them were distributed between pH 3.71 and 6.66. IEF profiles of FSH in the pituitaries varied with the stage in the estrous cycle. Especially at the time of serum FSH surge on the day of proestrus, most of the components decreased, while only a highly alkaline component showed an increase. When these FSH components were separated and their nature was examined by radioreceptor assay (RRA), radioimmunoassay (RIA) and gel filtration, differences were observed among these components in the RRA/RIA ratio and gel filtration profile. As a general tendency, the RRA/RIA ratio of the components became greater while the apparent molecular size became smaller, as their pI became higher. However, some highly acidic components showed a biphasic elution pattern and the most acidic one eluted the latest on gel filtration, suggesting that these components may be heterogeneous in terms of molecular size. The FSH concentration in sera collected at different stages in the estrous cycle was measured by both RRA and RIA. The RRA/RIA ratio was high when the serum immunoreactive FSH was low, and low during the FSH surge. From these findings, it is concluded that the quality of FSH molecules present in the anterior pituitary gland changes dynamically throughout the estrous cycle, especially during the period of serum FSH surge. Furthermore it is suggested that the type of FSH secreted from it also varies according to the stage in the estrous cycle.     

Variations in free secretory component levels in mucosal secretions of the rat

The present studies were conducted to compare the levels of free secretory component (SC) in a number of rat mucosal secretions and to determine whether SC content varies significantly during the four stages of the estrous cycle. Levels of SC, as measured by radioimmunoassay, were markedly different in various external secretions. Bile contained the highest amount, irrespective of whether SC was normalized to volume or protein. Concentrations of SC in saliva or uterine fluid from intact rats were approximately 20- to 30-fold less than measured in bile. When SC levels were normalized to protein, the SC to protein ratios in uterine, vaginal, and respiratory secretions were six to 18 times greater than values calculated in salivary and small intestinal fluids. Analysis of SC levels in mucosal secretions during the estrous cycle indicated significant variations occur in uterine and vaginal samples, but not in saliva or small intestinal secretions. In the uterine lumen, SC levels were highest at proestrus, partially elevated at estrus, and lowest at both days of diestrus. In contrast, vaginal SC levels were maximal at estrus and reduced at all other stages of the cycle. Immunoglobulin A content was also measured in uterine and vaginal secretions during the estrous cycle. Significant changes in IgA levels were found and these coincided with the changing pattern of SC. These results suggest hormones may modulate SC levels in reproductive tissues. In addition, our findings indicate variations in SC during the estrous cycle may direct the movement of IgA from tissue to lumen.     

Peripheral oxytocin in female baboons relates to estrous state and maintenance of sexual consortships

The neuro-hypophysial hormone oxytocin (OT) has been implicated in female reproductive and maternal behaviors and in the formation of pair bonds in monogamous species. Here we measure variation in urinary OT concentrations in relation to reproductive biology and socio-sexual behavior in a promiscuously breeding species, the chacma baboon (Papio hamadryas ursinus). Subjects were members of a habituated group of baboons in the Okavango Delta, Botswana. We collected behavioral data and urine samples from n = 13 cycling females across their estrous cycles and during and outside short-term, exclusive sexual consortships. Samples were analyzed via enzyme immunoassay (EIA) and we used linear mixed models (LMM) to explore the relationship between peripheral OT and a female's estrous stage and consortship status, her previous reproductive experience and fertility. We also used a Pearson's correlation to examine the relationship between OT concentrations of consorting females and their extent of behavioral coordination with their consort partners. The results of the LMM indicate that only estrous stage had a significant influence on OT levels. Females had higher OT levels during their periovulatory period than during other stages of their estrous cycle. There were no differences in the OT levels between consorting and non-consorting periovulatory females. However, among consorting females, there was a significant positive relationship between urinary OT levels and the maintenance of close proximity between consort partners. Our results suggest that physiological and behavioral changes associated with the initiation and maintenance of short-term inter-sexual relationships in baboons correspond with changes in peripheral OT.     

Gonadotropin-releasing hormone binding sites in ovaries of normal cycling and persistent-estrus rats

The gonadotropin-releasing hormone (GnRH) binding capacity in ovaries and pituitaries of normal cycling rats at different stages of the estrous cycle and in ovaries of persistent-estrus rats was measured using radioligand-receptor assay (RRA). Persistent estrus was induced either by neonatal administration of testosterone propionate (1.25 mg s.c.) on the second day of life or by a hypothalamic suprachiasmatic frontal cut made with Halász' knife. All animals were killed during the critical period (1400-1600 h), and GnRH receptor was assayed. GnRH receptor levels in both ovaries and pituitaries changed during the estrous cycle. The total number of ovarian GnRH binding sites was significantly higher in proestrus than in diestrus 1, the stage in which the lowest level was found. When binding sites were expressed in fmol/mg ovary, the highest level was observed in diestrus 2; however, no changes were observed during the estrous cycle when GnRH binding sites were expressed as fmol/mg protein. Changes noted were very similar to those demonstrated in pituitary GnRH receptors in our present and previous experiments. Higher levels of pituitary binding sites were found in diestrus 2 and proestrus than in estrus and diestrus 1. The changes in the GnRH receptor levels were more striking in the pituitary than in the ovaries. It appears that the total number of ovarian GnRH binding sites was not altered in either of the two persistent-estrus groups, but that their concentration was significantly higher (expressed in fmol/mg ovary or fmol/mg protein) than on any day during the estrous cycle.(ABSTRACT TRUNCATED AT 250 WORDS)     

The rat uterine oestrogen receptor in relation to intra-uterine devices and the oestrous cycle [proceedings

There are changes in the nuclear content of the estrogen receptor in the rat uterus during the estrous cycle that are associated with changes in its physiology. The changes correlate with the concentrations of circulating estradiol. It appears that uterotrophic response to estradiol is a function of the nuclear receptor. The insertion of an IUD leads to changes in the treated uterine horn which appear to be the result of an increased responsitivity to circulating estradiol. The presence of an IUD did not alter the estrous cycle, gonadotropin, or corpus luteum function. The intracellular distribution of the estrogen receptor was investigated in normal uterine horns and in the horns with devices throughout the estrous cycle. Groups of 30 Wistar rats had a silk suture fitted in the lumen of 1 uterine horn. After 14 days the progress of these estrous cycles was determined. Rats were grouped according to the stage of the cycle on the 4th day. Rats were then killed and the uteri removed. Cytosol receptors were measured. The capacity of the cytosol estrogen receptor to bind to oligo(dT)-cellulose was determined. Cytosol protein, nuclear protein, and DNA were measured. At all stages of the estrous cycle, the wet weight and cytosol receptor of the treated horns were greater than the control horns. A slight increase in the capacity of cytosol receptor to bind to oligo(dT)-cellulose was noted at proestrus. The response elicited by the IUD was not considered to be due to an estrogenic response since the changes observed were not accompanied by a corresponding increase in the content of nuclear receptor.     

Immunocytochemical localization of albumin in ovarian follicles of fertile rats

Summary The purpose of this study was to investigate whether albumin (Alb) can be detected in ovarian rat granulosa cells. Using immunocytochemistry and morphometrics, the percentages of Alb-positive follicles (follicle-index), of Alb-positive granulosa cells (granulosa-index), and of strongly reacting follicles (intensity-index) were evaluated in intact and regressing follicles of different diameter groups during different stages of the estrous cycle. In intact follicles, the follicle- and the granulosa-index increased from small-sized to large-sized follicles. Although the follicle-index did not change in any group during the stages of the estrous cycle, the granulosa-index was higher during proestrus than during the other stages. Intact follicles showed a stronger immunoreactivity than regressing follicles throughout the stages of the estrous cycle. Thus, Alb may be a requirement for the control of follicle growth in fertile rats. This Alb function may be attributable to Alb binding to specific cell-membrane components followed by the intracellular uptake of Alb-bound substances.Supported by a DFG grant no. Sp 232/2-2     

Sex and estrous cycle differences in the behavioral effects of high-strength static magnetic fields: role of ovarian steroids

Advances in magnetic resonance imaging are driving the development of higher-resolution machines equipped with high-strength static magnetic fields (MFs). The behavioral effects of high-strength MFs are largely uncharacterized, although in male rats, exposure to 7 T or above induces locomotor circling and leads to a conditioned taste avoidance (CTA) if paired with a novel taste. Here, the effects of MFs on male and female rats were compared to determine whether there are sex differences in behavioral responses and whether these can be explained by ovarian steroid status. Rats were given 10-min access to a novel saccharin solution and then restrained within a 14-T magnet for 30 min. Locomotor activity after exposure was scored for circling and rearing. CTA extinction was measured with two-bottle preference tests. In experiment 1, males were compared with females across the estrous cycle after a single MF exposure. Females circled more and acquired a more persistent CTA than males; circling was highest on the day of estrus. In experiment 2, the effects of three MF exposures were compared among intact rats, ovariectomized females, and ovariectomized females with steroid replacement. Compared with intact rats, ovariectomy increased circling; estrogen replacement blocked the increase. Males acquired a stronger initial CTA but extinguished faster than intact or ovariectomized females. Thus the locomotor circling induced by MF exposure was increased in females and modulated by ovarian steroids across the estrous cycle and by hormone replacement. Furthermore, female rats acquired a more persistent CTA than male rats, which was not dependent on estrous phase or endogenous ovarian steroids.     

The influence of estrogen on the hyperglycemic action of alloxan in female rats

The purposes of this study were to investigate (1) the relationship between estrogen and glucose levels in the circulation during an estrous cycle of the rat and (2) the effect of estrogen on the hyperglycemic action of alloxan. Three-month old Long Evans strain rats were used. The present study established for the first time the correlation between estrogen and glucose levels in the circulation during an estrous cycle. A significant (p less than 0.01) negative correlation was observed with the lowest glucose level at the proestrus stage where estrogen is at peak. The severity of hyperglycemia induced by alloxan was positively correlated with the circulating level of endogenous estrogen, but was negatively correlated with the fasting glucose level. A similar pattern was observed in ovariectomized female rats that were followed by estradiol implantation to achieve a constant level of circulating estrogen. It may be concluded from the present study that estrogen, under physiological conditions, participates in the regulation of glucose metabolism during various stages of the estrous cycle in the rats, and that glucose is likely able to protect the pancreatic beta cells of the animals against the hyperglycemic action of alloxan.     

Maternal-infant separation impedes changes in feeding behavior during estrous cycle of rats

Traumatic and stressful events during childhood are associated with the development of eating disorders. We conducted an animal study to test if association stress in childhood affects ingestive behavior later in life by using female rats that have an adjusted estrous cycle. First, electrical impedance of the vagina was conducted to test estrous cycle adjustment. Second, the effects of 6 h per day maternal separation from birth to weaning, which models a psychologically stressful experience in childhood, was used to test feeding behavior during an ovarian cycle in female adult rats with matched estrous cycles. Food and water intake in maternal separated and non-separated rats was measured in each estrous phase. Non-separated rats showed periodical changes, but maternal separated rats showed no significant changes in food and water intake during an estrous cycle. An opposing tendency for food and water intake was seen between maternal separated and non-separated rats. These observations suggest that electrical impedance of the vagina showed the highest value in the estrous phase of rats housed in a reversed light-dark cycle, and maternal separation was found to disturb changes in feeding behavior during the estrous cycle.     

Ovarian atrial natriuretic peptide during the rat estrous cycle.

The changes in ovarian levels of immunoreactive atrial natriuretic peptide (irANP) and arginine vasopressin (irAVP) were observed during the estrous cycle of rat. We also demonstrated the synthesis of ovarian ANP. In adult 4-day cycling rats, ovarian level of irANP was found to be the highest on proestrus and was to be the lowest on diestrus. Ovarian irANP level inversely correlated with ovarian level of irAVP. On reverse-phase HPLC, two distinct peaks of ovarian irANP, high and low molecular weight forms, existed in the each stage of the estrous cycle. However, no significant changes in plasma and atrial concentrations of ANP were observed during the cycle. The rat ovary contained mRNA coding for ANP. These data showing the synchronized cyclic change of ovarian irANP and irAVP with the estrous cycle suggest that the ovary locally synthesizes ANP and ovarian ANP may play regulatory roles on the follicular fluid dynamics.     

Estrous cycle stage-independent treatment of PMSG and hCG can induce superovulation in adult Wistar-Imamichi rats.

The estrous cycle influence on the number of ovulated eggs after injection of pregnant mare serum gonadotropin (PMSG) and human chorionic gonadotropin (hCG) was investigated in 12, 18, and 24 weeks old adult female Wistar-Imamichi (WI) rats. PMSG (150 IU/kg) was injected at metestrus, diestrus, proestrus, or estrus, followed by hCG (75 IU/kg) 55 h later. Ovulation was induced at all ages and stages of the estrous cycle. The number of ovulated eggs was not affected by stage for similarly aged rats, however, the number of ovulated eggs obtained after treatment decreased with age. These results demonstrate that the PMSG/hCG treatment can induce ovulation at any stage of estrous cycle in WI rats and efficient superovulation at 12 weeks of age.     

Prolactin messenger ribonucleic acid concentrations throughout the ovine estrous cycle: assessment relative to prolactin serum and pituitary amounts

Prolactin (PRL) mRNA concentrations were assessed by nucleic acid hybridization assays in pituitaries of ewes representing the defined stages of the ovine estrous cycle. Concomitantly, pituitary and serum PRL concentrations were measured in these ewes using radioimmunoassays. It was observed that PRL serum, pituitary and mRNA concentrations tended to increase near the time of the gonadotropin preovulatory surge, particularly between 24 hrs before behavioral estrus to 5 hours after estrus. However, the changes in PRL mRNA, serum and pituitary concentrations were shown not to be statistically significant. These data suggest that PRL production during the sheep estrous cycle is maintained without dramatic changes in synthesis or secretion.     

Effects of 5-HT1A receptor agonist and antagonist on anxiety in intact and ovariectomized female rats

The purpose of this work was to study the role of 5-HT1A receptors on the level of anxiety in adult intact and ovariectomized (OVX) female rats. The influence of chronic administration of 5-HT1A receptor agonist 8-OH-DPAT (0.05 mg/kg, s.c.) and 5-HT1A receptor antagonist NAN-190 (0.1 mg/kg, i.p.) given for 14 days alone or in combination with 17beta-estradiol (0.5 microg i.m./rat/day) was studied on behavior in the elevated plus maze. In intact females administration of NAN-190 resulted in significant increase in the number of enterings and the time spent on the open arms in every phase of the estrous cycle, however, 8-OH-DPAT failed to modify these parameters. In OVX females 8-OH-DPAT alone or in combination with 17beta-estradiol significantly increased the number of enterings and time spent on the open arms. On the contrary, NAN-190 alone or in combination with 17beta-estradiol in OVX females failed to evoke behavioral changes in the elevated plus maze. Thus, the 5-HT1A receptor antagonist NAN-190 induced anxiolytic effect in intact female rats, while 5-HT1A receptor agonist 8-OH-DPAT produced an anxiolytic profile on OVX rats. Results of this work specify the involvement of 5-HT1A receptors in behavioral mechanisms of anxiety in OVX female rats.     

Follicular growth and kinetics during the estrous cycle, pregnancy and postpartum in the Indian mole rat (Bandicota bengalensis)

Follicular growth and kinetics were studied in detail in the ovaries of the Indian mole rat (Bandicota bengalensis) during various stages of the estrous cycle; days 7, 12, 15, 19, and 21 of pregnancy; and day 2 postpartum. The sizes of follicles, oocytes, nuclei, and nucleoli were measured. In all rats, regression coefficients, a, and intercepts, b, were calculated in oocyte/follicle, oocyte nucleus/follicle and oocyte nucleus/oocyte regressions. The oocyte reached its maximum size when the average follicle diameter was 117 microns in nonpregnant rats and 131 microns in pregnant rats. The oocyte nucleus attained maximum size when the follicle diameter was 110 microns during the estrous cycle and 111 microns during pregnancy and postpartum. Maximum values of the diameter of the largest antral follicle and average diameter of the four largest antral follicles were observed during proestrus (473 and 442 microns, respectively) and on day 21 of pregnancy (611 and 538 microns, respectively). Chi 2 analysis showed that distribution of various types of follicles was not independent of the stage of the estrous cycle and pregnancy. In estrus and metestrus most of the follicles were between stages I and V. However, by diestrus and proestrus, follicles of all size groups developed. The numbers of stage I and II follicles did not differ as pregnancy advanced. More stage V follicles were present on day 12 than on day 7 of pregnancy; however, their numbers decreased by day 15. Afterwards, progressive increase of stage V and (VI + VII) follicles was observed until day 21. This was accompanied by the shift of follicles from stage (III + IV) on days 19 and 21 of pregnancy and even of stage II on day 2 postpartum. Wherever possible, the results have been compared with previous observations in various rodent species.     

Change in the electrical impedance caused by cornification of the epithelial cell layer of the vaginal mucosa in the rat

The electrical impedance in the vagina (EIV) is significantly high in the proestrus stage compared with other stages of the estrous cycle in rats. Therefore, the EIV can be used to detect the optimum day for mating. The relation between the EIV and the conditions of the epithelial cell layer of vaginal mucosa were investigated. The EIV was at a high level (over 3,000 omega) in vaginas in the proestrus stage in either intact or excised vaginal mucus. But it decreased (under 3,000 omega) after the epithelium of the vaginal mucosa was removed. The EIV of ovariectomized rats was low, but increased after Estradiol administration. The cornification of the epithelial cell layer of the vaginal mucosa occurred concurrently with the high EIV in the proestrus stage and after Estradiol administration. This indicates that the cornification of the epithelial cell layer of the vaginal mucosa may cause the elevation of EIV in the proestrus stage, the optimum day for mating in the rats.     

Acute and chronic estrogen supplementation decreases uterine sympathetic innervation in ovariectomized adult virgin rats

Uterine innervation undergoes substantial reorganization associated with changes in reproductive status. Nerves innervating the uterus are decreased in pregnancy and puberty, and even the normal rodent estrous cycle is characterized by fluctuations in numbers of myometrial nerve fibers. During the follicular (proestrus/estrous) phase of the estrous cycle, intact nerves are rapidly depleted and then return over the next 2-3 days in the luteal (metestrus/diestrus) phase. We hypothesize that uterine nerve depletion is initiated by increased circulating estrogen in the follicular phase. However, studies have not shown whether estrogen can reduce uterine innervation and, if so, whether the time course is compatible with the rapid changes observed in the estrous cycle. These questions were addressed in the present study. Mature ovariectomized virgin rats received 17-beta-estradiol as a single injection (10 microg/kg s.c.) or chronically from timed-release pellets (0.1 microg/pellet for 3 weeks sustained release). Total (protein gene-product 9.5-immunoreactive) and sympathetic (dopamine beta-hydroxylase-immunoreactive) uterine innervation was assessed quantitatively. Both total and sympathetic innervation was abundant in uterine longitudinal smooth muscle of ovariectomized rats. However, following acute or chronic estrogen administration, total and sympathetic fiber numbers were markedly decreased. This was not due to altered uterine size, as reductions persisted after correcting for size differences. Our results indicate that sympathetic nerves are lost from uterine smooth muscle after estradiol treatment in a manner similar to that seen in the intact animal during estrus and pregnancy. This suggests that the rise in estradiol prior to estrus is sufficient to deplete uterine sympathetic innervation.