Hormonal Priming Research Articles

Hormonal Modulation of the Cutaneous Initiation of Lordosis in Infant and Adult Rats

The purpose of these experiments is to compare the regional specificity (Experiment 1) and the hormonal modulation (Experiment 2) of the cutaneous initiation of lordosis in 4- to 6-day-old male and female rats (infants) and in 60- to 90-day-old female rats (adults). In Experiment 1, subjects were primed with 100 μg estradiol benzoate (EB) and 0.5 mg progesterone (P) and were denervated on the Waist (dermatomes L1-L3), Midriff (dermatomes T10-L3), Flanks (dermatomes L4-L6), or Sides (dermatomes T10-L6). In infants, there were no significant differences between males and females. Denervation of the Waist. Midriff, or Sides but not of the Flanks significantly decreased the percentage of subjects displaying lordosis, lordosis quotient (LQ), and mean lordosis duration; no significant differences were obtained among Waist-, Midriff-, or Sides-denervated infants. In contrast, denervation of the Sides but not of the Waist significantly decreased LQ and mean lordosis intensity among adults. In Experiment 2, Waist-denervated infants and their surgical Controls were treated either with 100 μg EB and 0.5 mg P or with the oil vehicle; Waist-denervated adults and their surgical Controls received either 100 or 10 μg EB (no P). Regardless of hormone treatment, denervation of the Waist significantly decreased LQ and lordosis duration in infants and decreased LQ and lordosis intensity in adults. In infants, the only effect of priming with EB and P was to increase the percentage of pups showing lordosis and lordosis duration among the surgical Controls. In contrast, priming with 100 μg EB significantly increased the percentage of rats displaying lordosis, LQ, and lordosis intensity among Waist-denervated adults. These data suggest that cutaneous input from the Waist is important for eliciting lordosis in both infant and adult rats, and that the importance of this input is modulated by hormone priming in adult but not infant rats.

Growth hormone releasing hormone priming increases growth hormone secretion in patients with Cushing's syndrome.

In patients with Cushing's syndrome, decreased growth hormone (GH) secretion is observed though the basic mechanism is unknown. In states of chronic deficiency of hypothalamic growth hormone releasing hormone (GHRH) release, a blunted GH response to exogenous GHRH has been reported; such impairment can be partially normalized by repetitive GHRH administration (priming). In order to clarify whether a deficit in hypothalamic release of GHRH is the basis of the decreased GH secretion in patients with Cushing's syndrome, GHRH plus pyridostigmine tests were undertaken, both before and after GHRH priming. GHRH (200 micrograms/day as a single s.c. injection) was given daily over 7 days. Two pyridostigmine (120 mg p.o.) plus GHRH (100 micrograms i.v.) tests were performed before and after priming to assess GH response. Eight patients (seven women, one man), with untreated Cushing's syndrome (six Cushing's disease, one autonomous bilateral adrenal hyperplasia, one adrenal adenoma), were studied. Plasma GH levels were measured by immunoradiometric assay. GHRH plus pyridostigmine-induced GH release was impaired in patients with untreated Cushing's syndrome (mean peak 5.2 +/- 1.4 mU/l, area under the curve (AUC) 472 +/- 96). Repetitive administration of GHRH over 7 days partially restored the GH response to the second pyridostigmine-GHRH test (mean peak 15.0 +/- 2.1 mU/l. AUC 1016 +/- 104), both P < 0.05. All of the eight Cushing's syndrome patients studied presented a higher GHRH plus pyridostigmine-induced GH secretion after priming. Repetitive administration of GHRH increases the pyridostigmine-GHRH-induced GH secretion in patients with Cushing's syndrome. This suggests that impaired hypothalamic release of GHRH is a contributing factor to the decreased GH secretion observed in chronic hypercortisolism.

The effect of estrogen treatment on scopolamine inhibition of lordosis

Previous evidence indicates that the cholinergic muscarinic antagonist, scopolamine, inhibits lordosis in female rats. In the experiments reported here, the effects of various doses and repeated administrations of estrogen on the scopolamine inhibition of lordosis were examined. In the first experiment, intraperitoneal injections of scopolamine (1 mg/rat) completely inhibited lordosis in ovariectomized rats primed with low doses of estradiol benzoate (0.25 or 0.5 μg for 3 days) and progesterone (500 μg). However, scopolamine was significantly less effective in inhibiting lordosis in females primed with a higher dose of estradiol benzoate (25 μg for 3 days) and progesterone (500 μg). When hormone priming was repeated on subsequent weeks, scopolamine continued to inhibit lordosis in females that received 0.25 μg estradiol benzoate but was less effective in females primed with 0.5 μg. Scopolamine failed to inhibit lordosis in females treated with 25 μg estradiol benzoate on these later tests. In the second experiment, various doses of scopolamine (1, 2, or 4 mg/rat) were administered intraperitoneally to females primed with the highest dose of estradiol benzoate (25 μg) and progesterone (500 μg). Lordosis was inhibited equally by all scopolamine doses during the first week. As in the first experiment, scopolamine failed to inhibit lordosis at all doses on subsequent weeks of testing. These results indicate that the ability of scopolamine to inhibit lordosis is reduced by increasing the dose or the number of estrogen exposures. Because higher doses of scopolamine failed to restore its inhibitory effect on lordosis an upregulation of muscarinic receptors by estrogen cannot account for the reduced effectiveness of scopolamine.

Induction of transforming growth factor-alpha gene expression in rat decidua is independent of the conceptus.

We have previously shown that decidua is the major site of transforming growth factor-alpha (TGF-alpha) gene expression at the feto-maternal interface during the early stages of pregnancy in the rat. The present study was undertaken to determine whether the presence of TGF-alpha mRNA in the decidua was in direct response to a signal derived from the conceptus. We therefore used the model of pseudopregnancy in rat, inducing decidualization in the absence of a conceptus. TGF-alpha mRNA expression was examined using Northern blot analysis, and TGF-alpha peptide was localized using immunohistochemistry. Pseudopregnancy was produced through standard hormonal priming followed by an artificial stimulus of intrauterine sesame oil or PBS to induce decidualization. Northern blot analysis demonstrated TGF-alpha mRNA expression specifically in the deciduoma beginning on the day of decidual stimulus (Day 4), increasing on Day 6, and continuing through Day 14. In contrast to decidua of normal pregnancy, an additional transcript of 3.0 kb was present in the deciduoma. Immunohistochemistry of tissues from Day 9 of pseudopregnancy revealed specific cytoplasmic immunoreactivity in the majority of stromal type decidual cells of the antimesometrial area, whereas mesometrial decidual cells were not immunoreactive. The results indicate that the induction of decidual TGF-alpha gene expression is not in direct response to a signal derived from the conceptus but is a de novo event associated with the decidual reaction, and that the resulting TGF-alpha peptide is present in the majority of stromal type antimesometrial decidual cells. These findings also suggest that TGF-alpha could be playing a role in proliferation and/or differentiation of the decidua.

Nursing posture is elicited rapidly in maternally naive, haloperidol-treated female and male rats in response to ventral trunk stimulation from active pups

Maternal responsiveness in rats can be induced in virgin females and males, without hormonal priming, following several days of cohabitation with pups. Because antagonism of dopamine (DA) facilitates nursing behavior in lactating rats, the response of nonlactating, maternally naive rats to effective stimulation of the ventral trunk (ventrum) from pups following similar treatment was investigated. Lactating dams, virgin females and males, both intact and gonadectomized, were treated with a catalepsy-inducing dose of haloperidol (5 mg/kg), a DA receptor antagonist, and tested with hungry pups 1 hr later. Subjects were placed over 8 pups and postures assessed every 3 min for 30 min. The nursing posture occurred in most subjects. Lactating and nonlactating females were similar in occurrence of the nursing crouch, though the intensity was somewhat higher in the former; females scored higher than males in terms of likelihood and intensity of crouching; and there was no effect of gonadectomy. The nursing posture was not elicited in intact virgin females if the stimulus pups were anesthetized or if the subjects were treated with saline instead of haloperidol. There were no sex differences in onset or intensity of catalepsy in response to the dose of haloperidol used. These results suggest that the nursing posture occurs reflexively, is not directly dependent upon ovarian hormones, and is diminished by the effects of androgens, prior and current.

Importance of progesterone and estrogen priming for the induction of maternal behavior by vaginocervical stimulation in sheep: Effects of maternal experience

The effects of treating ovariectomised nulliparous and multiparous ewes with progesterone and estrogen on maternal behavior with or without vagino-cervical stimulation were investigated. Following 48 h of estrogen treatment there was neither evidence for stimulation of maternal behavior, nor a reduction in aggressive behavior, towards lambs by either multiparous or nulliparous ewes compared with control treatment (injections of the oil vehicle). Following 5 min of mechanical vaginocervical stimulation, the multiparous estrogen-treated ewes showed both positive maternal responses (low pitch bleats, licking, sniffing and approaching the lamb) and a reduction in aggression (butts) and negative behavior (withdrawal from the lamb) towards the lambs, whereas the nulliparous ewes showed only a reduction in aggression and negative behavior. Neither group showed positive maternal responses following vaginocervical stimulation without steroid priming. When the ewes received two weeks of progesterone priming prior to estrogen treatment, both multiparous and nulliparous ewes showed reduced aggression towards, and withdrawal from, the lambs compared to the control condition, but no positive maternal responses apart from an increased sniffing of the lamb. After vaginocervical stimulation positive maternal responses showed by multiparous ewes were significantly potentiated compared to those shown following estrogen treatment alone. Nulliparous ewes remained unresponsive on positive maternal behaviors. These studies show that hormonal priming has little effect in inducing the onset of maternal behavior in multiparous or nulliparous sheep but is an essential prerequisite for vaginocervical stimulation to do so in multiparous animals.

Stimulation of Parthenogenesis in Mouse Ovarian Follicles by Inhibitors of Inosine Monophosphate Dehydrogenase1

The effects of hormonal priming and inosine monophosphate (IMP) dehydrogenase inhibitors on the meiotic maturation and parthenogenetic activation of mouse oocytes were examined in this study. In the first series of experiments, unprimed mice or mice primed 24 h with equine chorionic gonadotropin (eCG) received injections of the IMP dehydrogenase inhibitors, bredinin (Br) or mycophenolic acid (MA), followed by histological examination at 24 h, 48 h, and 72 h after drug administration. In both treatment groups, oocytes from nonatretic antral follicles were stimulated to undergo germinal vesicle breakdown by 24 h and became parthenogenetically activated as manifested by pronuclear formation and early cleavage divisions. The parthenotes underwent degeneration by 72 h. In the second part of this study, the effects of priming and drug treatment on parthenogenetic activation and subsequent developmental potential in vitro were examined. Mice were primed with eCG, and 24 or 48 h later received injections of Br or MA. Cumulus cell-enclosed oocytes were isolated 21-22 h later and assessed for maturation; those having undergone germinal vesicle breakdown were cultured and subsequently examined for embryonic development. In mice primed for 24 h, but not 48 h, Br and MA stimulated a significant number of oocytes to resume maturation in vivo; these subsequently underwent activation and developed to blastocysts in vitro. In another series of experiments, germinal vesicle-stage oocytes were isolated from primed or unprimed mice and cultured in vitro to permit spontaneous meiotic maturation. Nine percent of mature ova from 24-h-primed mice developed to 2-cell parthenotes; activation in ova from unprimed and 48-h-primed mice was considerably lower. A time-course experiment demonstrated that the extent of parthenogenetic activation in vivo following Br treatment was related to the period of time between drug injection and isolation of ova, the optimal period being 12 h. Neither Br nor MA had a direct activating effect on the oocytes as evidenced by an inability to induce parthenogenesis in vitro. Simultaneous injection of hCG with either Br or MA stimulated ovulation and prevented the parthenogenetic response. These data are consistent with the idea that conditions within the follicle promote parthenogenetic activation when the oocyte matures in the absence of gonadotropin stimulation.

Experience-hormone interactions and maternal behavior in rats

Three studies were conducted to determine the effects of reproductive condition and hormonal background on the acquisition and retention of a prior maternal experience. In the first study five experience conditions were compared. All animals gave birth and received either no postpartum contact with pups or 1 2 hr, 1 hr, 2 hr or 24 hr of pup contact and were tested for maternal behavior 10 days later. Animals receiving pregnancy and parturitional experience, but minimal social experience with young, exhibited significantly longer maternal onset latencies than did groups receiving 2 or 24 hr of prior experience; also, comparisons of 10- and 30-day retention intervals indicated that animals tested 10 days after a 24-hr experience exhibited shorter latencies than those tested 30 days later. Thus, the duration of the postpartum experience and the interval since prior experience both affect the level of maternal responsiveness shown. In the second study six groups of females were tested. Four groups were permitted one day of interaction with pups either after parturition (primiparous animals) or following pup induction procedures (nulliparous animals) and were tested for their maternal responsiveness to foster pups 25–35 days later, either on day 19 of a subsequent pregnancy or following resumption of estrous cycling. For most measures of maternal behavior there were significant main experience and test effects; experienced and pregnant animals exhibited shorter latencies to retrieve, lick and crouch over pups than did inexperienced and cycling animals, respectively. Significant interactions were also found for genital licking latency as well as for retrieval and crouch frequencies. Primiparous experienced females tested during pregnancy exhibited higher levels of these behaviors than any other group. In the third study four groups of ovariectomized nulliparous animals were primed with the “maternal” hormones, progesterone and estradiol, and were given either 1 day of maternal experience following pup induction of maternal behavior or no experience. Animals were tested for maternal behavior 23–35 days later either following priming with progesterone and estradiol or following control injections. Consistent with the second study, the group exhibiting the shortest maternal onset latency was the maternally experienced group tested under hormonal priming. These data indicate that maternal experiences are more persistent if they are obtained under hormonal priming and are more easily activated if tests occur under hormonal priming; for many of the measures the effects of the two conditions are additive. Ways in which hormones might act to promote these effects are discussed.

Gonadotrophin-binding components in porcine follicular fluid

The follicular fluid is an important milieu for the growing and maturing oocyte and granulosa cells. In this study we investigated: (1) the properties of gonadotrophin-binding sites in the supernatant fraction of porcine follicular fluid (pFF) and compared them with those of membrane-bound receptors, and (2) the relative changes that occur in pFF and granulosa cell receptor-binding activity following hormone priming of gilts. 125I-Labelled human chorionic gonadotrophin (hCG) and 125I-labelled ovine FSH (oFSH) binding to particulate and supernatant fractions of pFF were hormone-specific and saturable. The concentration of 125I-labelled hCG-binding sites was roughly 50-fold higher in particulate than in supernatant fractions of pFF. However, 30-40% of the total 125I-labelled hCG-binding activity in pFF was present in the supernatant fraction of commercial batches of pFF. 125I-Labelled oFSH binding to pFF membranes was markedly higher than to supernatant fractions. Binding of 125I-labelled hCG and 125I-labelled oFSH to granulosa cells and supernatants of pFF showed a time-dependent variation in response to hormone priming. The results suggest that gonadotrophin-binding sites in the supernatant fraction of pFF have properties similar to those of their membrane-bound counterparts. 125I-Labelled hCG-binding activity in the supernatant fraction of pFF was shown to be more stable than detergent-solubilized LH/hCG receptors, even in glycerol-preserved preparations. Based on a number of criteria, we have speculated that pFF may have components which may be similar in structure to the extracellular domain of the LH/hCG receptor.

Cycloheximide blocks the retention of maternal experience in postpartum rats

Two studies were done to determine the effects of cycloheximide (CYX), a protein synthesis inhibitor, on maternal experience effects in rats. In the first study eight groups received a 2-h maternal experience 36 h after cesarean (c)-section and two groups received no post c-section experience. Among the experienced groups, two received icv injections of CYX or saline (SAL) 30 min before the maternal experience, two received CYX or SAL 10 min after the experience, and two received the injections 24 h after the experience. One inexperienced group received CYX and the other received SAL 36 h after c-section. Tests for maternal behavior occurred 10 days after c-section. CYX was not able to block or disrupt the "acquisition" or expression of ongoing maternal behavior during the 2-h experience phase. However, CYX was able to block the long-term "retention" of a 2-h maternal experience if the drug was present during or immediately after the experience, prior to "consolidation." The second study investigated the effects of CYX administered immediately after the maternal experience on the expression and retention of maternal behavior 4 and 6 days after c-section, to determine whether the hormonally mediated short-onset latencies of the 4-day group would be blocked by CYX. Eight groups of animals were tested for maternal behavior. Four were tested 4 days after c-section and four were tested 6 days after c-section. Within each of these groups two were experienced and two inexperienced; within each experience condition one group received CYX and one received SAL. Day 4 groups exhibited shorter onset latencies than Day 6 groups. There was also a CYX-SAL difference in maternal onset latencies among experienced Day 6 groups but not among Day 4 groups. These data indicate that the blocking effects of CYX can be seen only when hormonal priming of maternal behavior is no longer in evidence.

Maternal behaviour in ewes following Caesarian section

Lambs of 8 multiparous and eight primiparous Merino ewes were delivered by Caesarian section on the 143rd–149th day of gestation. Seven multiparas showed maternal behaviour and accepted lambs within 6 h of delivery and the other accepted its lamb by 3 days. No primiparous ewe showed maternal behaviour within 3 days, and only 2 came to tolerate the presence of their lambs by 5 and 8 days. The study shows that stimulation of the birth canal by passage of the lamb during birth is not essential for the onset of maternal behaviour in multiparas, but may be necessary in primiparas. The results indicate a deficiency in current knowledge about the hormonal priming necessary to induce the onset of maternal behviour; they also indicate that previous maternal experience plays a major role in this induction.

Hormonal Control of Sexual Behavior in the Female Rat: Molecular, Cellular and Neurochemical Studies1

The present era of molecular research on steroid hormone action originates from the demonstration that there are intracellular protein receptors that bind steroid hormones and carry them to sites in cell nuclei where they regulate gene expression (Jensen and Jacobson, 1962; Toft and Gorski, 1966; Jensen et al., 1968; O’Malley and Means, 1974). Researchers of steroid hormone action in brain tissue have taken advantage of this revolution in biochemistry and cell biology and have found a way to understand the actions of gonada! and adrenal steroids on neural cells in cellular and molecular terms. However, the road has not been an easy one. The difficulties stem from the extreme complexity and anatomical heterogeneity of the brain, and the precise and highly localized neural networks involved in governing behavior. There also have been conceptual problems caused by a common tendency to regard the hormone as a stimulus and the behavior it regulates as a response, a relationship that implies temporal immediacy. However, because a hallmark of steroid hormone-regulated behaviors is their long latency and duration in relation to hormone priming, it has been necessary to look at the role of hormones in a different light. More than 40 years ago, the preeminent pioneer in elucidating hormones’ effects on behavior, Frank Beach, anticipated the current view of steroid hormone action by writing:

Estrogen priming affects the sensitivity of midbrain central gray neurons to microiontophoretically applied LHRH but not beta-endorphin.

In vivo single-unit extracellular recording was used to assess neuronal membrane sensitivity at the level of the midbrain central gray (MCG) to the iontophoresis of luteinizing hormone releasing hormone (LHRH) and beta-endorphin (beta-END). The percentage of change in firing rate was evaluated to determine the effect of exogenously administered estradiol benzoate (EB) and EB plus progesterone (EB + P) on the membrane sensitivity of these MCG neurons to LHRH and beta-END. Ovariectomized adult female rats were primed with EB or EB + P, or nonprimed, 24-48 h prior to recording. EB priming significantly altered the membrane sensitivity of neurons in the MCG to LHRH by increasing the number of cells excited compared to the EB + P group and the nonprimed controls (p less than 0.005). The addition of P appeared to negate this effect. Hormonal priming did not alter the response profile for beta-END iontophoresis. The results suggest an estrogen-dependent sensitivity to LHRH at the MCG which translates into an increased electrical output, ultimately facilitating lordosis behavior. P treatment dampens this excitation. beta-END's effect on neuronal membrane excitability at the MCG was not distinctly characterized under the hormonal conditions our study evaluated and may reflect a regulatory role under physiological extremes.

Brain lateralization in primates and its evolution in hominids

Recent studies suggest that vocal communication and visuospatial processing are lateralized to left and right hemispheres respectively in monkeys of the genus Macaca, as they are in humans. The fundamental neurological substrate that forms the basis for complex cerebral asymmetries in Homo sapiens may therefore have been established remarkably early in anthropoid evolution. The tendency toward cortical lateralization has been greatly elaborated in human evolution, such that at least 90% of extant humans are right-handed. Numerous data support an association of the left human hemisphere with time-sequencing, language skills, certain neurochemical asymmetries, and specific psychiatric disorders. The right hemisphere, on the other hand, is associated with holistic processing, visuospatial and musical abilities, emotional processing, and its own neurochemical and psychiatric properties. Although a controversial topic, there appears to be slight but significant sexual dimorphism in certain skills associated with cortical lateralization in humans. Females excel at language and fine motor skills, as well as emotional decoding and expression; males are relatively adept at composing music and exhibit visuospatial and mathematical skills. Various scenarios that account for these differences are reviewed, and it is concluded that dimorphism in these behaviors may be due in part to hormonal priming involved in prenatal gender differentiation.

Sex hormone priming prior to the combined hypoglycaemia test.

The insulin hypoglycaemia test (IHT) was performed on 3 groups of short stature children. One group was unprimed with sex steroid hormones, a second group received 17 beta-oestradiol, while a third group received testosterone. The dosage of insulin was adjusted to produce a nadir in blood glucose of reversible 1 mmol/L. When this level is achieved plasma growth hormone (GH) responses less than 10 mU/L are not improved by either priming procedure. It is suggested from the data that there is no place for a diagnosis of a partial GH deficiency state. When the IHT is combined with Gn-RH and TRH infusion the data derived may indicate GH-RH deficiency alone or additionally a CRF deficiency. Alternatively a pituitary insensitivity to these releasing substances or a pituitary synthetic failure of all trophic hormones may be adduced. Unless a releasing hormone is deficient and the pituitary is shown to be able to respond to its synthetic analogue, treatment with the available analogues will fail to give the desired clinical response.

Induction of ovulation during anoestrus in two breeds of sheep with multiple injections of LH alone or in combination with FSH.

The gonadotrophic requirements for the induction of ovulation and formation of a viable corpus luteum in two breeds of seasonally anoestrous sheep of differing fecundity was investigated. Welsh Mountain (n = 20) and Damline ewes (n = 19) were given LH or FSH either alone or in combination. Luteinizing hormone was injected i.v. at an increasing frequency for 72 h (one injection every 3 h for 24 h, one every 2 h for 24 h, and one every hour for 24 h) and FSH was injected in an identical manner for the first 36 h of treatment. Exogenous LH alone and in combination with FSH induced a preovulatory LH surge in all 19 ewes and ovulation in 18 out of 19 ewes of both breeds. However exogenous FSH alone was ineffective. The incidence of normal corpus luteum function in ewes induced to ovulate was low and not related to treatment, timing or magnitude of the LH/FSH surge. It is concluded that in both breeds studied it is the infrequency of LH pulses which limits the development of preovulatory follicles during seasonal anoestrus, that the requirement for FSH remains unknown, and that the induction of inadequate corpora lutea during seasonal anoestrus reflects either defects in hormonal priming of the preovulatory follicle and/or inappropriate luteotrophic support after ovulation.

Facilitation of lordosis by estradiol in the mesencephalic central gray

Ovariectomized female hamsters received unilateral implants of estradiol aimed at the mesencephalic central gray (MCG). Postoperative levels of lordosis and ultrasonic vocalization were used to evaluate implant effects on sexual receptivity and proceptivity. Females with large MCG implants showed higher levels of receptivity than females with similar implants at control sites. In addition, females with small MCG implants showed little receptivity while the implant served as the sole source of estrogen, but diverged from controls by showing elevated receptivity during supplemental treatment with low systemic doses of estradiol. These results suggest that estradiol implants in the MCG facilitate receptivity if, and only if, accompanied by exposure of other brain areas to low estrogen levels. In turn, this suggests that the MCG, though not a self-sufficient site for the hormonal priming of lordosis, does modulate sexual motivation by mediating facilitatory effects of estrogen on receptivity and mating.

Immunocytochemical localization and determination of hormone-induced synthesis of the sulfated oviductal glycoproteins.

Secretory products of the oviduct provide part of the milieu for the critical events of fertilization and embryo development. Past work from this laboratory has indicated that three large sulfated glycoproteins can be isolated from rabbit oviductal fluid and are synthesized by oviductal epithelium incubated in vitro. These three glycoproteins are antigenically similar. This paper presents evidence for their localization within the oviductal tissue and their hormonal control of synthesis. Utilizing goat antiserum to these oviductal glycoproteins and the immunoglobulin-horseradish peroxidase bridge method, these macromolecules have been localized in the ampulla and isthmus of the oviduct. Ten days after ovariectomy an oviduct was removed for immunolocalization. The does were then given estradiol for the next 4 days and the second oviduct was removed. Oviducts treated with estradiol showed immunostaining of virtually all of the secretory granules within the secretory cells of the isthmus. While light level immunocytochemistry suggested the possibility of two populations of secretory granules within the ampulla because some of the granules did not show immunocytochemical staining, the more sensitive immunocytochemistry at the electron microscopic level showed staining of all granules of the ampulla and isthmus. Absorption of the antiserum with pure antigen prevented all staining. After ovariectomy and hormone withdrawal, most of the immunostaining was lost in the isthmus and virtually no staining in the ampulla was observed. Oviductal cell suspensions were made to evaluate incorporation of [35S] sulfate and [3H] leucine as a function of hormonal priming of the tissue. Estrogen-primed oviductal cells incorporated the sulfate and leucine into these specific glycoproteins.(ABSTRACT TRUNCATED AT 250 WORDS)

Dissociation between the direct stimulatory and inhibitory effects of a gonadotropin-releasing hormone analog on ovarian functions

The paradoxical effects of gonadotropin-releasing hormone (GnRH) on the ovary have hitherto been believed to result from different regimens of administration; an acute treatment was shown to stimulate the ovary while chronic administration of the hormone inhibited LH-induced responses. In the present report we demonstrate that a single injection of a GnRH analog (D-Ala 6)des-Gly 10-GnRH-N-ethylamide (GnRHa, 2 μg/rat) is sufficient to obtain a significant inhibition (75%) of hCG-induced ovulation in PMSG-primed, either intact or hypophysectomized, immature rats. Inhibition of ovarian development, in terms of growth and ovulation, by multiple injections with GnRHa (2 μg/rat, twice daily for 3 days) could be obtained only upon administration of the hormone at early stages of follicular development, i.e. concomitantly with the PMSG injection. When administered after PMSG, GnRHa could not inhibit the ovary but rather induced ovulation by itself in the absence of hCG. A 12–24 h delay in initiation of GnRHa treatment triggered 65% of the rats to ovulate while a delay of 48 h resulted in 100% ovulation. Under both regimes of GnRHa administration, either the inhibitory or the stimulatory, the oocytes of the treated rats were induced to resume meiotic maturation. Since under the inhibitory regime ovulation did not occur, maturation was followed by a massive degeneration of the oocytes trapped within their follicles. These findings demonstrate that the follicular stage of development rather than the dose and/or duration of GnRHa administration determines whether GnRHa inhibits ovarian growth and ovulation, while the competence of the oocytes to respond to the GnRHa stimulus and mature is independent of hormonal priming.

Hormonal interaction with stimulus and situational factors in the initiation of maternal behavior in nonpregnant rats.

Previous hormonal studies have identified the hormonal and stimulus factors mediating the initiation of maternal behavior but have failed to reduce hormone-induced latencies of nonpregnant females to less than 1-2 days of continuous pup exposure. For the purpose of testing whether this delay is due to an olfactory-vomeronasal-mediated aversive reaction to pups like that found in untreated virgins, estrogen-injected hysterectomized-ovariectomized (HO-EB) nonpregnant females were subjected to olfactory-vomeronasal deafferentation. Median latencies were reduced to 0 and 1.5 hr compared with 72 hr for HO-EB nondeafferented females, which indicates that normally after HO-EB treatment, tendencies to initially avoid pup contact remain strong. Next, the hypothesis was explored that experiences during late pregnancy and/or parturition interact with hormonal priming to modify pup avoidance. Nonpregnant HO-EB females that had been exposed to pregnant-parturient females for 2 wk were tested under conditions simulating parturition. A high percentage rapidly initiated maternal behavior, but conditions during testing proved more important than prior exposure to pregnancy/parturition. The contributions of three stimulus/situation factors were analyzed: pup age--newborn versus 3-8 day; method of pup presentation--four at once versus staggered introduction; and time of day--lights versus dark phase. Hormonally treated but not sham-treated females initiated maternal behavior most rapidly when first exposed to one newborn in the nest during the light phase (76% within 1.5 hr). Prepartum caesarean-delivered females, however, responded maternally to four 3-8-day-old pups outside the nest, which indicates that additional factors operate at parturition.