A selective androgen receptor modulator enhances male-directed sexual preference, proceptive behavior, and lordosis behavior in sexually experienced, but not sexually naive, female rats

Androgens influence many aspects of reproductive behavior, including sexual preference of females for males. In oophorectomized women with sexual desire disorder, testosterone patches improve libido, but their use is limited because of adverse side effects. Selective androgen receptor modulators offer an improved safety profile for both sexes: enhancing libido and muscle and bone growth in a manner similar to steroidal androgens but with fewer adverse effects, such as hirsutism, acne, and prostate growth. The current study investigated the action of a novel selective androgen receptor modulator (LGD-3303 [9-chloro-2-ethyl-1-methyl-3-(2,2,2-trifluoroethyl)-3H-pyrrolo-[3,2-f]quinolin-7(6H)-one]) on male-directed sexual preference, proceptivity, and lordosis behavior of female rats. LGD-3303 is a nonsteroidal, nonaromatizable, highly selective ligand for the androgen receptor and effectively crosses the blood-brain barrier. Gonadectomized female rats were treated with LGD-3303 (3-30 mg/kg) or vehicle by daily oral gavage. Results showed that LGD-3303 treatment enhanced sexual preference of females for males but only if females had previous sexual experience. This occurred after 1 or 7 d of treatment. In contrast, preference for males was inhibited by LGD-3303 treatments of sexually naive females. The LGD-3303 increase in male preference was blocked by pretreatment with the androgen receptor antagonist flutamide. LGD-3303 treatment increased lordosis and proceptivity behaviors in ovariectomized females primed with suboptimal doses of estradiol benzoate plus progesterone. These data support the concept that LGD-3303 can stimulate aspects of female sexual behavior and may serve as a potential therapeutic for women with sexual desire disorders.

Ethanol exposure during the last week of gestation in the rat: inhibition of the prenatal testosterone surge in males without long-term alterations in sex behavior

In utero ethanol exposure decreases the prenatal testosterone (T) surge in male rats. To determine the functional significance of this suppression, we measured sex behavior in adult litter representatives of pregnant rats that were administered a fortified liquid diet containing 35% ethanol-derived calories from day 15 of gestation through parturition. Control dams were pair-fed an isocaloric liquid diet with the ethanol calories replaced by sucrose. Results from the behavioral studies showed that gonadally intact fetal alcohol-exposed (FAE) males exhibited little masculine sex behavior in the first of four weekly sessions. However, their behavior in the subsequent three tests was indistinguishable from pair-fed controls. Lordosis quotients in the same males following castration and estrogen and progesterone treatment were under 10%. In castrated FAE females, no effects of prenatal ethanol exposure were observed in masculine behaviors following androgen replacement or feminine sex behaviors following estrogen and progesterone replacement. Additional studies measured the duration of prenatal ethanol exposure necessary to inhibit the prenatal T surge in order to determine whether the inhibition was due to a direct effect of the drug. Results revealed an inhibition of the surge in males exposed to ethanol from days 14 through 20 of pregnancy, days 14 through 16 of pregnancy, or days 17 through 20 of pregnancy. A normal surge of T was observed on days 18-19 of gestation in control fetuses. These findings indicate that ethanol does not have to be present in blood at the time of the surge to have an inhibitory effect. They also reveal that the surge can be inhibited with as little as 24-36 h of ethanol exposure prior to its normal appearance on day 18 of gestation. In spite of this inhibition of the prenatal T surge, the behavioral results indicate that normal masculinization and defeminization of sex behavior occurs in FAE males exposed to ethanol after the beginning of the period of differentiation of the hypothalamus and testes.

Prenatal ethanol exposure induces a sexually dimorphic effect on daily water consumption in prepubertal and adult rats

Previous studies have shown that female rats consume significantly more water than males on a weight basis. Because exposure to alcohol during the last week of gestation is associated with incomplete behavioral defeminization in male rats, we examined daily water intake in fetal alcohol-exposed (FAE) males and females. Time-pregnant multiparous Sprague-Dawley dams were administered an ethanol liquid diet containing 35% ethanol-derived calories from day 14 through parturition. At 80 days of age, daily water consumption of FAE males and female litter representatives was measured for 7 days. FAE males, but not females, consumed significantly more water than their pair-fed counterparts. Subsequent experiments determined that the increased water consumption in FAE males is present prepubertally, persists into mature adulthood, and is not influenced by prenatal or postnatal castration. Chronic estrogen treatment induced large increases in water consumption, but consumption of FAE males remained elevated over elevated pair-fed male consumption, indicating that pituitary sensitivity to estrogen was not increased in FAE males. Morphometric studies of hypothalamic nuclei containing vasopressin cells revealed no long-term effects of prenatal ethanol exposure on the volume of the supraoptic nucleus or paraventricular nucleus in males, nor was an effect observed in the ventromedial nucleus measured as a control. In FAE females, the volume of the paraventricular nucleus was significantly smaller than chow-fed controls. Whereas baseline plasma and pituitary arginine vasopressin (AVP) levels of FAE animals and pair-fed controls were not significantly different, AVP content was significantly reduced in the septal/bed nucleus region in brains of FAE animals of both sexes. Overall, these data indicate that prenatal ethanol exposure increases male water consumption in the absence of alterations in basal plasma AVP.

A novel endogenous corticotropin release inhibiting factor

ACTH is the major regulator of the body's adaptive response to stress and the physiological stimulus for glucocorticoid secretion. A hypothalamic corticotropin release inhibiting factor (CRIF) that inhibits ACTH synthesis and secretion has long been postulated but was not characterized until recently. We have recently identified a 22 amino acid peptide, prepro-thyrotropin releasing hormone (TRH) 178-199 that inhibits basal and stimulated ACTH synthesis and secretion in vitro and stress-induced ACTH secretion in vivo. Prepro-TRH 178-199 is abundant in several brain regions, including the external zone of the median eminence, where its concentration changes in response to stress. We propose that this peptide is a physiological regulator of ACTH production: an endogenous CRIF. Because prepro-TRH 178-199 is encoded within the same precursor as TRH, its expression is likely to be negatively regulated by thyroid hormones leading to changes in endogenous glucocorticoid levels. Streptococcal cell wall (SCW)-induced inflammation, a model of rheumatoid arthritis (RA), was alleviated after long-term thyroxine treatment. Inversely, a hypothyroid milieu led to decreased basal hypothalamic-pituitary-adrenal activity, but increased expression of IL-1 beta and MIP-1 alpha, specific markers for RA in humans. These results suggest that this putative CRIF may be an important component in the development of RA and that regulation of prepro TRH may be highly relevant to the development of other autoimmune diseases that are also exacerbated by low endogenous glucocorticoid levels.

Maternal adrenalectomy eliminates a surge of plasma dehydroepiandrosterone in the mother and attenuates the prenatal testosterone surge in the male fetus

Previous work has established a number of sex-related deficits in immune function, behavior, and endocrine responses to stress in the offspring of dams exposed to ethanol. To examine the potential role of maternal glucocorticoids as a mediator of these sexually dimorphic effects in the fetus, we examined the influence of prenatal alcohol exposure in the presence or absence of maternal glucocorticoids on fetal plasma corticosterone (CORT) production. An additional question to be addressed by these studies was whether maternal adrenalectomy could eliminate the known inhibition by ethanol of the prenatal surge of plasma testosterone in male fetuses. Pregnant dams were adrenalectomized (ADX) or sham-adrenalectomized on gestational day (G) 7 and placed on a liquid diet containing 35% ethanol-derived calories or pair-fed an isocaloric control diet throughout the experiment. On G18, G19, and G21, plasma levels of CORT, testosterone, and dehydroepiandrosterone (DHEA) were measured in male and female fetuses and their mothers. Ethanol administration consistently increased maternal plasma CORT levels but did not significantly alter CORT levels in the fetus. Maternal ADX resulted in compensatory increases in fetal CORT levels that were lower in fetuses of ADX dams on alcohol, suggesting a direct effect of ethanol on fetal pituitary-adrenal activity. There were no significant sex differences in fetal plasma CORT levels in response to any of these manipulations. A novel surge of maternal plasma DHEA was found on G19 that was absent in plasma from ADX dams. In spite of the absence of a surge on G19, plasma DHEA levels of ADX dams rose from very low levels at G18 to levels on G21 that were significantly higher than in Sham dams. A normal testosterone surge was observed in male fetuses on G18 and G19 from sham-adrenalectomized dams administered the pair-fed diet. However, this surge was greatly attenuated in males administered ethanol and also in male fetuses from ADX dams. These results reveal a direct inhibitory influence of ethanol on fetal CORT secretion as well as on the prenatal testosterone surge in males. Furthermore, these studies demonstrate the presence of a surge of DHEA in the pregnant rat. Overall, these data suggest that there is a critical adrenal factor in the rat that regulates the maternal surge of DHEA on G19 and the prenatal testosterone surge of male fetuses on G18-19.

Sex differences in visual recognition memory: support for a sex-related difference in attention in adults and children

The selectivity hypothesis of Meyers-Levy (1989) proposes that cognitive sex differences reflect underlying differences in information processing between males and females. Males are considered to be more likely to organize information in a self-related manner, whereas females are more likely to adopt a comprehensive approach to information processing. We tested this hypothesis in children (10-15 years) and adults using recognition memory tasks. Tests were devised which employed male-oriented objects, female oriented objects, or random objects. In both the child and adult samples, females performed significantly better than males on tests using random and female-oriented objects. Males performed at the level of females only when tested for recognition of male-oriented objects. These results demonstrate that this sex difference is present prior to puberty and support the concept of sex differences in information processing.

Alterations in the estrogen sensitivity of hypothalamic proenkephalin mRNA expression with age and prenatal exposure to alcohol

Studies suggest that exposure to alcohol in utero causes reproductive and neuroendocrine deficits in adult female rats. The ventromedial nucleus of the hypothalamus (VMN) is an estrogen-sensitive brain region which is regarded as a primary locus for modulating female reproduction. Proenkephalin (PE) mRNA expression in the VMN is dramatically increased by estrogen and this elevation is thought to be involved in modulating female reproductive behavior and neuroendocrine function. To examine whether prenatal alcohol exposure has long-term effects on the ability of estrogen to influence hypothalamic PE mRNA levels, female rats at 2-3, 6-7 or 15-18 months of age, derived from alcohol- or control-fed dams, were studied. 7 days following ovariectomy, animals received either estrogen or sham treatment for 2 days prior to sacrifice. PE mRNA levels in the VMN and striatum were determined by in situ hybridization histochemistry. Film autoradiogram density, numbers of PE mRNA-expressing cells and exposed silver grains/cell were analyzed. Estrogen treatment increased hybridization density, the number of PE mRNA-expressing cells and PE mRNA (grains) level/cell in the VMN of normal adult female rats. In old rats, estrogen increased the number of PE mRNA-expressing cells without up-regulating PE mRNA grain density/cell. In fetal alcohol-exposed (FAE) female rats, the number of cells that expressed PE mRNA did not increase following estrogen treatment at any age. Elevation of grain density/cell following estrogen was observed in FAE animals but only at 7-8 months of age. Overall, these data indicate that the estrogen responsiveness of PE mRNA expression in the VMN declines with age and, furthermore, prenatal exposure to alcohol blunts estrogen's effects on PE mRNA expression in the adult VMN. These finding may help to explain the mechanisms underlying the loss of reproductive function observed in FAE females.

Inhibition of stress-induced neuroendocrine and behavioral responses in the rat by prepro-thyrotropin-releasing hormone 178-199

A corticotropin release-inhibiting factor (CRIF) in brain has been postulated for several decades, based on increased plasma levels of ACTH and corticosterone after hypothalamic-pituitary disconnection. Recent in vitro studies indicate that prepro-TRH178-199 may function as an endogenous CRIF, prompting us to examine stress-related neuroendocrine and behavioral responses after in vivo administration to the adult male rat. Animals that were administered prepro-TRH178-199 intravenously 5 min before restraint stress exhibited a significant attenuation of stress-induced elevations of ACTH, corticosterone, and prolactin, as compared with controls infused with vehicle, whereas thyroid-stimulating hormone (TSH) secretion was not changed. In behavioral studies of stress responsiveness, either the vehicle or prepro-TRH178-199 was administered intracerebroventricularly (ICV) 5 min before testing. In the open field, prepro-TRH178-199 significantly increased grooming, locomotor activity, rearing, and sniffing behaviors. In the light/dark box, it significantly increased the time animals spent in the light compartment and increased the number of crossings between the light/dark compartments. In the plus maze, the peptide significantly increased the amount of time animals spent in the open arms. The same dose of peptide, administered ICV, had no effect on peripheral hormone release in response to restraint stress. Overall, these results support a role for prepro-TRH178-199 in the inhibition of the neuroendocrine responses to stress at the level of the pituitary and indicate that it has central modulatory influences over stress-related behaviors.

Androstenedione synergizes with stress or prenatal drug exposure to retard fetal growth: role of IGF

Pregnant Sprague-Dawley dams were implanted with a Silastic capsule (3 or 10 mm) containing androstenedione (AN) or cholesterol prior to being administered one of several treatments that create an endocrine profile of stress: maternal exposure to alcohol, pair feeding (PF), cocaine (COC), or restraint stress (RS). Controls (chow fed, CF) were left undisturbed during pregnancy. Treatments were administered from day 14 to day 22 of gestation. Fetuses were delivered by cesarean section on day 22. Results revealed that administration of AN to pregnant dams at a dose that does not influence fetal growth by itself can retard fetal growth in the presence of alcohol, PF, COC or RS. Data indicate that these effects are not directly attributable to changes in adrenocorticotropin (ACTH) or corticosterone levels. Preliminary results suggest a role for insulinlike growth factor (IGF) binding proteins (IGFBPs). Overall, these data demonstrate that AN can synergize with drugs and/or stress to enhance intrauterine growth retardation (IUGR). One underlying cause of this synergism between stress-related environmental events and androgenic actions on fetal growth may be increased expression of IGFBPs, which can sequester IGFs, thereby inhibiting their trophic actions on fetal and/or placental tissue.

Absence of postnatal testosterone fails to demasculinize the male rat's corpus callosum

We had previously shown that elimination of testosterone from embryonic day 17 through adulthood reduced the midsagittal area of the male rat corpus callosum (CC). However, day 1 castration, performed after the 2-h post-birth testosterone surge, was without effect. To elucidate the contribution of this surge on the CC, male rats were delivered by cesarean section and castrated within 20 min. This procedure eliminated the 2-h postnatal rise in testosterone levels. The prenatal surge in testosterone, which occurs on embryonic day 18, remained intact. In adulthood, callosal area was examined in castrate males, sham males, and intact females. Castrate males and sham males had significantly larger CCs as compared to females. The two male groups did not differ from each other. Body weight was significantly higher in sham versus castrate males, establishing the effectiveness of the castration. These results show that hormonal organization of the CC in the male is the result of the independent action of prenatal testicular androgens, and suggest that the end of this period marks the end of callosal sensitivity to testicular hormone influence. In addition, this report documents sexual dimorphism of the CC in a third rat strain.

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.

Sex difference in daily water consumption of rats: effect of housing and hormones

Females rats consume more water than males per day when consumption is indexed to body weight. We examined the developmental expression of this sex difference as well as the organizational and activational influences of testosterone (T). The amount of water consumed from weaning to adulthood exhibited a linear decrease with age in both sexes. The development of a sex difference in water consumption was evident immediately after weaning in singly housed animals, but did not emerge until about Day 42-45 in group-housed animals, when females began to consume greater amounts of water than males. Castration at weaning had minimal effects on the sex difference. Treating dams with testosterone propionate (TP; 0.3 mg/kg; E15-E20) resulted in a significant increase in adult water consumption in offspring of both sexes, but the sex difference remained. Overall, these data indicate that gonadal steroids are not the primary organizational influence on this sex difference. The greater water consumption in females is consistent with other studies demonstrating sex differences in plasma vasopressin levels, as well as differences in vasopressin sensitivity.

Gonadotropin-releasing hormone mRNA and gonadotropin beta-subunit mRNA expression in the adult female rat exposed to ethanol in utero

Previous studies have demonstrated that exposure of female rats to ethanol in utero results in long-term deficits in reproductive function, including a delayed onset of puberty and an early onset of acyclicity. In the present studies, we determined if changes in reproduction are correlated with changes in gonadotropin-releasing hormone (GnRH) mRNA expression in the brain or gonadotropin subunit mRNA expression in the anterior pituitary gland. We used in situ hybridization histochemical techniques to examine the density of GnRH mRNA and the distribution of GnRH mRNA-containing cells in the basal forebrain, and reverse transcription-polymerase chain reaction (RT-PCR) to quantitate the beta-subunit mRNA of luteinizing hormone (LH beta) and follicle-stimulating hormone (FSH beta) in the anterior pituitary gland of adult (3 months of age) fetal alcohol-exposed (FAE) female rats. For GnRH mRNA measurements, animals were gonadectomized 4 days before use. Three groups of animals were examined. FAE females were derived from pregnant dams fed a liquid diet containing 35% ethanol-derived calories from gestational day 14 until parturition. Dams of control animals were either pair-fed (PF) an isocaloric diet with sucrose substituted for ethanol or maintained on normal laboratory rat chow [chow-fed (CF)]. Serial blood samples taken by indwelling right atrial cannulae demonstrated significantly smaller pulses of LH (p < 0.05) and FSH (p < 0.05) in ovariectomized FAE females at 3 months of age, compared with PF and CF controls. Distribution of GnRH mRNA-containing cells was mapped throughout the forebrain, and the number of autoradiographic silver grains/cell was determined.(ABSTRACT TRUNCATED AT 250 WORDS)

Plasma testosterone surge and luteinizing hormone beta (LH-beta) following parturition: lack of association in the male rat

Studies examining the role of luteinizing hormone (LH) in the initiation of the postnatal surge of testosterone in the male rat have produced ambiguous results. We examined the pattern of postnatal LH secretion in the newborn male rat, coincident with plasma testosterone levels, using a specific monoclonal antibody for LH-beta. In some males, we attempted to block LH secretion and the postnatal testosterone surge by injecting males with a gonadotropin-releasing hormone (GnRH) antagonist, an LH antibody or progesterone immediately after delivery by cesarean section on day 22. Following injection, animals were immediately sacrificed (time 0) or housed in a humidified incubator maintained at 30 degrees C until sacrifice at 60, 120, 240, 360 or 480 min after delivery. Plasma from individual animals was measured subsequently for LH-beta and testosterone by radioimmunoassay. Results revealed a postnatal surge of testosterone which peaked at 2 h after delivery in males from all treatment groups. This testosterone surge was not accompanied by a postnatal rise in plasma LH-beta in any group. Administration of the GnRH antagonist or the ethanol vehicle produced a transient drop of approximately 25% in LH-beta levels at 60 min but did not decrease the postnatal testosterone surge in the same animals. Additional studies in untreated males and females born by cesarean section or natural birth also failed to reveal a postnatal rise in plasma LH-beta during the first 3 h after birth. Plasma levels in both sexes were significantly lower in animals delivered by cesarean section compared to natural birth.(ABSTRACT TRUNCATED AT 250 WORDS)

Loss of reproductive competence at an earlier age in female rats exposed prenatally to ethanol

Previous studies have shown that prenatal ethanol exposure can partially masculinize or defeminize neurobehavioral development of female rats. An early age of onset of anovulation is one of the primary characteristics of partial defeminization. Consequently, we examined the occurrence of anovulation in fetal alcohol-exposed (FAE) female rats at 2, 6, and 12 months of age using both vaginal cytology as well as wheel-running behavior. We assessed the ability of estrogen and progesterone to elicit proprioceptive behaviors and lordosis at 2 and 17 months of age. Female subjects were derived from Sprague-Dawley dams administered an ethanol liquid diet (35% ethanol-derived calories), a pair-fed isocaloric liquid diet, or fed lab chow from days 14 to 22 of gestation. Litter representatives were placed in a computer-monitored wheel-running apparatus under a 12-hr lighting schedule from 49 to 60 days of age. Vaginal smears were taken from littermates during this same period. This same procedure was conducted again from 180 to 196 and from 380 to 396 days of age, except that vaginal cytology was examined in the same animals immediately after wheel-running behavior was studied. At approximately 2 months of age, a normal cyclical pattern of wheel-running, characteristic of 4- to 5-day estrus cycles, was observed in all animals. No differences were detected in mean activity levels during the wheel-running period. This was accompanied by normal cyclic vaginal cytology and normal proprioceptive behaviors and lordosis. At 6 months of age, FAE females exhibited significantly reduced wheel-running.(ABSTRACT TRUNCATED AT 250 WORDS)

Fast glucocorticoid feedback inhibition of ACTH secretion in the ovariectomized rat: effect of chronic estrogen and progesterone

The purpose of this study was to determine whether estrogen and progesterone influence fast glucocorticoid negative feedback regulation of the ACTH and corticosterone (CORT) responses to stress. Mature rats were ovariectomized and 6 weeks later implanted with 17 beta-estradiol (E2, 0.5 mg), E2 and progesterone (P, 100 mg; E2 + P group) or placebo pellets (OVX). Seven days later rats were subjected to a single or repeated intermittent footshock stress (0.2 mA, 15 s duration, 0.5 s on). The repeated stress was of the same intensity and duration, and was applied either during the time domain of the rate-sensitive fast glucocorticoid feedback when plasma CORT levels are rising (5 min after the onset of the first stress), or at the time of peak CORT response (15 min) to the initial stress. Plasma ACTH and CORT were measured from serial samples. Estrogen replacement alone or in combination with progesterone lowered the immediate (t = 5) ACTH and CORT response to a single stress in ovariectomized animals. The second stress applied 5 min after the initial stress produced net ACTH responses similar to those obtained after a single stress in the OVX and E2 + P-replaced hormone groups, while total ACTH responses were lower in the E2-treated group. In ovariectomized animals, a facilitation of ACTH response by a prior stress is apparent in response to a footshock 15 min later, when the integrated ACTH secretion is significantly greater than the response measured after a single shock, or after a repeated shock 5 min apart. Anterior pituitary proopiomelanocortin (POMC) mRNA levels were lower in groups with E2 or E2 + P replacement compared to OVX animals. In contrast, hypothalamic corticotropin-releasing factor (CRF) mRNA levels did not increase significantly. However, hypothalamic glucocorticoid receptor (GR) mRNA levels increased after 17 beta-estradiol treatment, and this increase was reversed by progesterone. These results suggest that prior stress leads to both a fast-feedback inhibition and a facilitation of the subsequent stress response. In the absence of gonadal hormones this facilitation is balanced by fast-feedback inhibition during the glucocorticoid fast-feedback time domain, and is unmasked outside of this time domain. Estrogen suppresses POMC mRNA synthesis leading to a decrease in the availability of releasable ACTH, thereby reducing the facilitation. Progesterone may counter this effect of estrogen by decreasing the efficacy of the fast rate-sensitive glucocorticoid negative feedback.

Adrenalectomy reverses stress-induced suppression of luteinizing hormone secretion in long-term ovariectomized rats

An inhibitory effect of stress on reproductive function is well established. This inhibition involves activation of the hypothalamic-pituitary-adrenal (HPA) axis, which leads to a suppression of LH secretion. It has been proposed that this suppression is mediated by a direct effect of CRF that is independent of glucocorticoid actions. We tested this proposition by examining plasma LH levels in adult rats that were both ovariectomized (OVX) and adrenalectomized (ADX). Each animal was surgically implanted with an indwelling atrial cannula and exposed to intermittent foot shock for 100 min. Blood samples were drawn just prior to putting the animals into the test cage and then at 20-min intervals. Results revealed normal castrate levels of plasma LH in both ADX and ADX/OVX animals prior to shock. A significant shock-induced suppression of LH was observed in OVX animals within 20 min after the onset of shock and remained throughout the duration of the session. In contrast, no evidence was obtained for a suppression of LH in OVX/ADX animals at any time point. Additional studies demonstrated a marked suppression of LH in experimentally naive OVX/ADX females implanted with corticosterone capsules for 2 weeks prior to blood sampling. Overall, these results support a primary role for glucocorticoid actions in the stress-induced inhibition of reproductive function.

Decreased postnatal testosterone and corticosterone concentrations in rats following acute intermittent prenatal hypoxia without alterations in adult male sex behavior

The prenatal and postnatal testosterone surges in the male rat are associated with neurobehavioral sexual differentiation of the brain. Both surges can be attenuated by maternal stress or other environmental factors that activate the maternal and/or fetal hypothalamic/pituitary/adrenal (HPA) axis during the last week of gestation. Since hypoxia is known to activate the HPA axis, we studied its effect during gestation on sexual differentiation in the male rat. We examined the influence of intermittent hypoxic exposure during gestation with respect to the postnatal testosterone surge and corticosterone levels, and subsequent development of adult reproductive and nonreproductive sexually dimorphic behaviors. Plasma testosterone and corticosterone concentrations of male neonates were measured after maternal exposure to acute, intermittent, prenatal hypoxia (9% O2 6 h/day from Day 15 to 21 of gestation). Relative to normoxic controls, acute, intermittent, prenatal hypoxia significantly attenuated the postnatal testosterone surge. Postpartum plasma corticosterone levels in these animals were also suppressed. In adulthood, prenatally hypoxic animals exhibited normal masculine sex behavior. Lordosis behavior in response to estrogen and progesterone priming was not significantly different between treatment groups. Saccharin preference, a nonreproductive, sexually dimorphic behavior, was not significantly influenced by prenatal hypoxic exposure. These results demonstrate that in the male acute intermittent prenatal hypoxia attenuates the postnatal testosterone surge. However, this reduction failed to result in significant alterations in the expression of sex related behaviors in adulthood.

Androgen regulation of adrenocorticotropin and corticosterone secretion in the male rat following novelty and foot shock stressors

To examine mechanisms responsible for sex differences in hypothalamo-pituitary-adrenal (HPA) axis responsiveness to stress, we studied the role of androgens in the regulation of the adrenocorticotropin (ACTH) and corticosterone (CORT) responses to foot shock and novelty stressors in gonadectomized (GDX) or intact male F344 rats. Foot shock or exposure to a novel open field increased plasma ACTH and CORT, which was significantly greater in GDX vs. intacts. Testosterone (T) or dihydrotestosterone propionate (DHT) treatment of GDX animals returned poststress levels of ACTH and CORT to intact levels. Estrogen treatment of GDX males further increased poststress CORT secretion above GDX levels. There was no difference in the ACTH response of anterior pituitaries from intact, GDX, and GDX+DHT animals to CRF using an in vitro perifusion system. There were no differences in beta max or binding affinity of type I or II CORT receptors in the hypothalamus or hippocampus of intact, GDX, or GDX+DHT groups. These data demonstrate an effect of GDX on hormonal indices of stress. The increased response in GDX rats appears to be due to the release from androgen receptor mediated inhibition of the HPA axis. This inhibition by androgen is not due to changes in anterior pituitary sensitivity to CRH, nor to changes in type I or type II corticosteroid receptor concentrations.

Decreased postnatal testosterone surge in male rats exposed to ethanol during the last week of gestation

Prenatal alcohol exposure in the rat is known to interfere with the neurobehavioral sexual differentiation of the male brain. Because normal sexual differentiation of the male brain requires adequate levels of perinatal testosterone, we examined the effect of prenatal ethanol exposure on (1) the postnatal surge of testosterone and (2) the in vitro secretion of testosterone in response to luteinizing hormone (LH) stimulation of testes from fetal alcohol exposed (FAE) animals and controls. Sprague-Dawley dams were administered a fortified liquid diet containing 35% ethanol-derived calories, a pair-fed (PF) isocaloric liquid diet, or given ad libitum access to dry lab chow (CF). Dams were administered the liquid diets from days 7 or 14 through parturition. The postnatal surge of testosterone in FAE males was studied only in animals exposed to ethanol from day 14 through parturition. In the first experiment, FAE and PF males and females were delivered by cesarean section on day 22 of gestation (E22) and trunk blood collected at 0, 60, 120, and 240 min after parturition. Experiment 2 measured plasma testosterone in male pups that were killed at 0, 60, 120, 240, 360, and 480 min after delivery. Results showed that the postnatal testosterone surge of FAE males in both experiments was significantly attenuated compared with PF controls. No effect of prenatal ethanol was observed in female offspring. Female testosterone levels were several fold lower than male littermates, and no evidence of a postnatal testosterone surge was observed. Production of testosterone from testes was studied using an automated perifusion system.(ABSTRACT TRUNCATED AT 250 WORDS)

Altered adult sexual behavior in the male rat following chronic prenatal hypoxia

The last week of gestation is a critical period for the sexual differentiation of the brain in the rat. Exposure to prenatal stress during this period has been shown to demasculinize and/or feminize adult male sexual behavior. Many of the neurochemical and endocrine responses to hypoxia are similar to that observed under stressful conditions such as restraint stress. Therefore, we examined the postnatal consequences on reproductive and nonreproductive sexually dimorphic behaviors in male offspring of dams exposed to chronic hypoxia during the last week of gestation. In addition, we examined sensorimotor development in offspring of both sexes. Pregnant Sprague-Dawley dams were exposed to continuous hypoxia (10.5% O2 from gestational day 15 to 21). Offspring were weaned at 22 days of age and group housed. Behavioral tests were conducted with littermate representatives. In adulthood, male rats prenatally exposed to hypoxia had significantly delayed initiation latencies of masculine sexual behavior and decreased number of ejaculations, but did not display a significant increase in feminine sex behavior potentials. Developmentally, animals exposed to prenatal hypoxia did not differ significantly from controls with respect to day of eye or ear opening, or the in times of righting reflex, negative geotaxis or cliff avoidance. Wire hanging latencies in hypoxic exposed animals were significantly greater than controls around the time of eye opening, but did not differ at earlier or later ages. A significant effect of hypoxia was detected on stride length at 95 days of age, but other aspects of gait patterns were similar to controls. No group differences in gait patterns were observed at 17 or 45 days of age. In addition, no significant differences were observed in open field activity, circadian locomotor activity, saccharin preference, or Morris water maze test. This hypoxia regimen did not influence the occurrence of the prenatal or postnatal surge of plasma testosterone. Overall, these results provide some evidence that, in males, mild, chronic prenatal hypoxia may result in incomplete masculinization of adult reproductive behavior in the absence of overt changes in perinatal testosterone surges.

Decreased tolerance to ethanol-induced hypothermia in long-term castrate male rats

A potential role for central stores of vasopressin in the development of tolerance was studied in the long-term castrate rat. Vasopressin stores in the septal region are known to be dramatically depressed following long-term castration. Sprague-Dawley male rat littermates were castrated at 26 days of age or given a sham surgery. Experiments began when animals reached 130 days of age. Tolerance to the hypothermic effects of ethanol occurred in intact but not castrate animals over the course of six daily IP injections of 3.0 g/kg ethanol. Both groups exhibited tolerance to the length of time needed to return to baseline temperature over the 6 days of ethanol injections. Tolerance to this effect of ethanol was still evident in intact animals but not castrates following another injection of ethanol 1 week later. No tolerance developed to the rebound hyperthermia that occurred in both groups. Blood ethanol levels did not differ significantly between castrate and intact littermates administered a single dose of ethanol. Overall, these results support the hypothesis that endogenous vasopressin is involved in the development of some aspects of tolerance to ethanol.

Comparison of two weeks versus one week of prenatal ethanol exposure in the rat on gonadal organ weights, sperm count, and onset of puberty

Sprague-Dawley dams from Harlan Ind. (Indianapolis, IN) were administered a fortified ethanol liquid diet containing 35% ethanol derived calories for two weeks (E-2) beginning on day 7 or one week (E-1) beginning on day 13 of gestation and continuing through parturition. Control dams were pair-fed an isocaloric liquid diet containing no ethanol during these periods or remained on lab chow and water. E-2 dams consumed an average of 13.52 g ethanol/kg bwt during the first week of exposure (days 8-14) and 12.50 g ethanol/kg bwt the second week (days 14-20). E-1 dams consumed significantly less than E-2 dams during the second week (9.75 g/kg; p < 0.0001). Although the lower consumption in E-1 dams led to a significant decrease in maternal weight gained during the few days of pregnancy compared to E-2 dams, birthweights of E-1 offspring were significantly heavier than those of E-2 offspring (p < 0.05). No effect of ethanol was detected on anogenital distance at birth in either sex. Puberty was delayed in female offspring of both E-1 and E-2 dams (p < 0.01) as measured by age of vaginal opening. These data suggest that the primary teratogenic actions of ethanol in the rat on fetal growth, as well as delayed puberty in females, occur in the last week of gestation. In adult E-2 males, testis weight was significantly heavier than all other groups when indexed to body weight. No effect of prenatal ethanol exposure was observed on the indexed weights of prostate, epididymis, or seminal vesicles.(ABSTRACT TRUNCATED AT 250 WORDS)

Delayed onset of puberty and subtle alterations in GnRH neuronal morphology in female rats exposed prenatally to ethanol

Fetal alcohol exposed (FAE) animals exhibit physiological and behavioral deficits associated with reproduction including alterations in LH secretion and decreased sex behavior. Such deficits led us to examine the morphological characteristics and number of GnRH neurons in female rats prenatally exposed to ethanol. Sprague-Dawley dams (Harlan, Indianapolis, IN) were administered a fortified liquid diet (Sustacal) containing 35% ethanol derived calories from day 7 through parturition. Controls were pair-fed a similar isocaloric diet containing no ethanol during this period or allowed access to dry food pellets ad lib. Compared to both control groups, puberty was found to be significantly delayed in females that were exposed prenatally to ethanol. The median age of vaginal opening for chow-fed and pair-fed controls was 34-35 days compared to 38-39 days for FAE animals. A subgroup of these females was selected at 44 days of age on the basis of delayed onset of puberty and compared with pair-fed controls for the number and morphology of GnRH-immunoreactive staining (ir) neurons in the medial preoptic area (MPOA) and the diagonal band of Broca (DBB), regions which contain the majority of GnRH-IR cells in the rat brain. In both areas, light microscopic study revealed no differences in GnRH-IR cell number, nor were differences detected among the groups in the number of bipolar versus unipolar cells. However, a significant increase was observed in FAE brains compared to controls in the ratio of GnRH-IR neurons with irregular processes compared to smooth cell contours.(ABSTRACT TRUNCATED AT 250 WORDS)

Behavioral sequelae in young rats of acute intermittent antenatal hypoxia

Several studies have examined behavioral sequelae of acute or chronic pre- or postnatal hypoxia. However, few of these tested a large battery of behavioral functions, particularly those following relatively mild, intermittent hypoxia. Also, in few studies were the hypoxic pups cross-fostered or the experimenter blinded as to experimental group. In addition, in almost no studies were concomitant hypoxic-induced brain biochemicals measured. The present study tested the hypotheses that mild, intermittent antenatal hypoxia can lead to long-term alterations in neurobehavioral development, as well as neurochemical changes.

Neonatal ovariectomy and pituitary-adrenal responsiveness in the adult rat

Litters of female rat pups were handled daily from birth to weaning. When 12 days old the pups were ovariectomized or received sham surgery. At 70 days sham and ovariectomized animals were decapitated immediately or placed within a novel environment for 10, 20, or 40 min before decapitation. Basal plasma levels of androstenedione in ovariectomized animals were approximately half that of intact sham controls, and stress caused only a small rise in androstenedione in this group. Androstenedione levels in ovariectomized animals were consistently at or below the lower sensitivity of the radioimmunoassay, indicating that circulating levels of androstenedione in the female rat are primarily of ovarian origin. Basal ACTH and corticosterone levels did not differ significantly between the two groups. However, stress-induced levels of ACTH and corticosterone were significantly depressed in ovariectomized subjects compared to controls following exposure to the novel environment. Furthermore, while ACTH levels started to return to baseline by 40 min in controls, this effect was not observed in ovariectomized animals. These findings demonstrate that prepubertal removal of ovarian humoral factors can have a long-term impact on the responsiveness of the hypothalamic-pituitary-adrenal axis to stress.

Prenatal lead exposure in the rat during the third week of gestation: long-term behavioral, physiological, and anatomical effects associated with reproduction

Sprague-Dawley dams were administered lead acetate (0.1%) in their drinking water from Day 14 of gestation to parturition to determine whether exposure of the fetus to elevated lead (Pb) levels during a period of rapid differentiation of the hypothalamic-pituitary-gonadal (HPG) axis would disrupt HPG function in adulthood. At birth, offspring from 20 Pb-treated and 10 control dams were weighed and 2 litter representatives from each sex were fostered to untreated dams. Animals were weaned at 26 days of age and subsequently group housed by sex and treatment. Blood Pb levels in prenatally exposed pups were below the limits of detectability at weaning. Female offspring from Pb-treated dams were found to have a significant delay in the day of vaginal opening. In a sample of lead exposed females, 50% were found to exhibit prolonged and irregular periods of diestrous which was accompanied by an absence of observable corpora lutea when they were euthanized at 83 days of age. Male offspring from these dams were found to have decreased sperm counts at 70 and 160 days of age and to exhibit significantly less territorial scent marking and masculine sex behavior in adulthood compared to controls. Azoospermia was observed in 1 lead exposed animal at 70 days of age and 2 animals at 160 days. Enlarged prostates were observed in Pb-exposed males measured at 160 days, but other sex organ weights were normal. Volume of the sexually dimorphic nucleus of the preoptic area of the hypothalamus in adulthood was significantly reduced by approximately 35% in Pb-exposed males. Pulsatile release of gonadotropins, measured in castrated adult animals of both sexes, revealed irregular release patterns of both FSH and LH in some Pb animals which were not observed in controls. The overall pattern of results suggests that multiple levels of the HPG axis can be affected by exposure to Pb during a period of gestation when structures related to the HPG axis are undergoing rapid proliferation. These data indicate that lead exposure during this period places the exposed animal at significant risk for reduced reproductive capacity in adulthood.

Body temperature differentially affects ethanol sensitivity in both inbred strains and selected lines of mice

Offsetting ethanol-induced hypothermia in five inbred strains of mice changed ethanol sensitivity within strains and markedly reduced differences between strains in brain sensitivity to hypnotic ethanol doses. The present study extended this work to mice selectively bred for sensitivity and resistance to ethanol-induced loss of righting reflex (LORR) and hypothermia. In all experiments LORR duration and ethanol concentrations at return of righting reflex were measured after i.p. hypnotic ethanol doses and exposure to 22 or 34 degrees C. In experiment 1, C57BL/6J, A/HeJ, 129/J, LS/lbg and SS/lbg mice were given 4.2 g/kg ethanol. In experiment 2, the same mouse genotypes were tested with different ethanol doses (2.5-4.9 g/kg) selected to produce an equivalent degree of impairment (60 min LORR duration). In experiment 3, HOT and COLD lines of mice were given 4.0 g/kg ethanol. In agreement with previous work, offsetting hypothermia reduced differences between genotypes in ethanol sensitivity. Comparisons within genotypes indicated that ethanol sensitivity in C57, A/He, SS, HOT and COLD mice increased as body temperature increased. In contrast, ethanol sensitivity in 129 and LS mice decreased as body temperature increased. These results extend previous findings indicating that body temperature during intoxication contributes to differences between genotypes in ethanol sensitivity. The present findings also suggest that there are qualitative differences in the effects of temperature on ethanol sensitivity within genotypes.

Prenatal inhibition of hypothalamic sex steroid uptake by cocaine: effects on neurobehavioral sexual differentiation in male rats

Several adrenergically active drugs have been shown to prevent the masculinizing and/or defeminizing effects of testosterone on brain sexual differentiation. We examined the ability of the neuronal norepinephrine uptake blocker, cocaine, to produce similar effects. The ability of cocaine to inhibit sex steroid incorporation into the hypothalamus during a critical period for sexual differentiation of the brain was examined in females treated at birth with testosterone. Sixty minutes after administration, cocaine was observed to inhibit both testosterone and estradiol incorporation into the hypothalamus by approximately 50%. Long-term consequences of prenatal cocaine exposure were studied by injecting Sprague-Dawley dams twice daily with 3, 10 or 30 mg/kg of cocaine hydrochloride on days 15 through 20 of gestation and examining the offspring. In adulthood, cocaine-exposed males, but not females were found to exhibit significantly less marking behavior than controls. Cocaine-exposed males in the 10 mg/kg group tested for sex behavior exhibited demasculinization in some aspects of the behaviors tested. Measurement of plasma hormone levels in this group revealed elevated levels of plasma LH, but normal levels of FSH and testosterone. No differences were observed in cocaine-exposed males with respect to sex organ or adrenal weights, but thymus was approximately 25% smaller compared to control males at 80 days of age. In a separate experiment, dams were treated with 3 mg/kg of cocaine twice daily from days 15 through 21 of gestation and half of the male pups received additional injections twice a day for the first 5 days postnatally.(ABSTRACT TRUNCATED AT 250 WORDS)

Interaction of naltrexone with postnatal administration of testosterone and estrogen on neurobehavioral sexual differentiation in rats

The present study examined whether some effects of gonadal sex hormones on neurobehavioral sexual differentiation might be mediated by endogenous opioids. Male and female pups were administered sesame oil, testosterone propionate (TP; 25 micrograms) or estradiol benzoate (EB; 10 micrograms) on postnatal Days 2 and 3. Half of each group was also administered naltrexone (N; 50 micrograms) twice daily on these two days. Females were studied for effects of the treatments on puberty. Males and females were studied in adulthood for open field behavior, daily water intake, and saccharin consumption and preference for 0.125, 0.25, and 0.50% saccharin solutions. TP treatment significantly delayed the date of vaginal opening, whereas EB treatment significantly accelerated the date. N treatment potentiated this effect of TP, but had no effect in EB treated females, nor did it influence the anovulatory sterility produced by both hormone treatments. N treatment alone had no effect on puberty in females or open field behavior of either sex. The drug produced an overall increase in female saccharin consumption and preference, but no effect was observed in males on these measures. Both TP and EB treatment produced marked increases in daily water consumption in females, an effect which was significantly attenuated by N treatment. Effects of both hormones on saccharin consumption were sex dependent and partially antagonized by N treatment. Finally, we observed a sex difference in daily water intake wherein females were found to consume approximately 20% more water on a body weight basis in a 24-hr period than males. Postnatal TP and EB treatment increased adult daily water consumption in females above the level of controls. This increase was partially antagonized by N. Treatment with N alone had no effect on female water consumption, but produced a small decrease in male consumption. Overall, these results provide preliminary evidence that some organizational effects of TP and EB on nonreproductive sex differences may be mediated by endogenous opioids.

Prenatal exposure to a low-frequency electromagnetic field demasculinizes adult scent marking behavior and increases accessory sex organ weights in rats

Pregnant Sprague-Dawley dams were exposed to a low-level, low-frequency pulsed electromagnetic (EM) field (15 Hz, 0.3 msec duration, peak intensity 8 gauss) for 15 min twice a day from day 15 through day 20 of gestation, a period in development that is critical for sexual differentiation of the male rat brain. No differences in litter size, number of stillborns, or body weight were observed in offspring from field-exposed dams. At 120 days of age, field-exposed male offspring exhibited significantly less scent marking behavior than controls. Accessory sex organ weights, including epididymis, seminal vesicles, and prostate, were significantly higher in field-exposed subjects at this age. However, circulating levels of testosterone, luteinizing hormone, and follicle-stimulating hormone, as well as epididymal sperm counts, were normal. These data indicate that brief, intermittent exposure to low-frequency EM fields during the critical prenatal period for neurobehavioral sex differentiation can demasculinize male scent marking behavior and increase accessory sex organ weights in adulthood.

Low birthweight in rats induced by prenatal exposure to testosterone combined with alcohol, pair-feeding, or stress

Pregnant Sprague-Dawley dams were exposed to a liquid ethanol diet (35% ethanol-derived calories), an isocaloric pair-feeding regimen, restraint stress, or no treatment during the last week of pregnancy. Dams in each group received injections of testosterone propionate (TP) or the oil vehicle from days 15 through 20 of gestation. Birthweights of pups from dams administered TP and also exposed to alcohol, pair-feeding, or restraint stress were significantly depressed by as much as 40 percent compared to oil-injected counterparts. Prenatal exposure to alcohol, pair-feeding, or restraint stress in the absence of TP did not significantly depress birthweight, nor was birthweight depressed in animals from dams injected with TP but exposed to no other treatment. Results are discussed with respect to an inhibition of fetal growth produced by a possible synergism between activation of the hypothalamic-pituitary-adrenal axis and elevated androgen levels.

Alcohol exposure in utero results in diminished T-cell function and alterations in brain corticotropin-releasing factor and ACTH content

The long-term teratogenic effects of prenatal ethanol exposure during the last week of gestation on immune responsiveness and levels of pituitary ACTH and hypothalamic corticotropin-releasing factor (CRF) were examined in Sprague-Dawley rats. Immune responsiveness was measured by T-lymphocyte proliferation in response to mitogenic stimulation with Con A (3 micrograms/ml) in spleen and thymus cells of 21-old-day male rats who were exposed to alcohol in utero. The proliferative response was 8-fold lower in spleen and twofold lower in thymus cells from alcohol-exposed animals compared to responses measured in control rats. Thymus weight was significantly smaller at birth in alcohol exposed males, but significantly larger at 21 days of age compared to controls. Alterations in the content of ACTH and CRF, hormones, known to be direct or indirect modulators of immune responsiveness, were also observed in alcohol exposed males. Hypothalamic content of CRF and pituitary content of ACTH were significantly lower in alcohol exposed males on postnatal Day 1, but hypothalamic ACTH content was significantly higher compared to controls. These results indicate that alcohol exposure during the last week of gestation can produce alterations of the hypothalamic-pituitary-adrenal function in addition to teratogenic effects on the immune system which have been previously observed only with a much longer alcohol exposure regimen.

Testosterone dose-dependency of sexual and nonsexual behaviors in the gonadotropin-releasing hormone antagonist-treated male rat

The testosterone dose-dependency of several mating and nonmating behaviors was examined in the male rat, chemically castrated with a GnRH antagonist analog. Graded doses of testosterone enanthate (TE) were given to male rats to reinstate behaviors abolished by GnRH antagonist treatment. GnRH antagonist treatment alone markedly lowered serum LH, FSH and T concentrations and ventral prostate and testis weights. Open field behaviors were not significantly affected by GnRH antagonist treatment or castration. Scent-marking behavior was markedly suppressed by both castration and GnRH antagonist and restored by the lowest dose of TE (0.05 mg). All measures of male sexual behavior were impaired by GnRH antagonist treatment and castration and restored by the lowest dose of TE (0.05 mg). The doses of TE required to restore normal ventral prostate weights and testis weights were higher than those required to maintain scent marking and mating behaviors. No direct behavioral effects of the GnRH antagonist, other than those that can be explained by GnRH antagonist-induced suppression of testosterone were observed. The finding that sexual and nonsexual behaviors in the male rat have different testosterone requirements from those maintaining spermatogenesis and fertility may have significant implications for contraception.

Perinatal aromatase activity in male and female rats: effect of prenatal alcohol exposure

Fetal alcohol exposure has been shown to produce long-term feminizing and demasculinizing effects on male rat behaviors which are organizationally dependent upon perinatal androgen levels. Such exposure has previously been shown to suppress the normal surge of testosterone during the critical prenatal period. Since defeminization of male rat behavior is dependent upon estrogen derived from the aromatization of testosterone in brain, brain aromatase activity was measured during the perinatal period in males and females exposed to alcohol beginning on Day 14 of gestation. Aromatase activity was measured in whole hypothalamus of fetuses from Day 16 through 20 of gestation and in the hypothalamic preoptic area and amygdala of animals 6-12 hr postparturition. Hypothalamic aromatase activity was elevated in fetal alcohol exposed males compared to controls on Days 18 and 19 of gestation and on postnatal Day 1. No effect of prenatal alcohol exposure was found in females. A sex effect in aromatase activity in the amygdala was evident on Day 1 when activity was found to be greater in males than females. Overall, these findings indicate that fetal alcohol exposure will elevate regional brain aromatase activity in males, but not females during the perinatal period of neurobehavioral sexual differentiation.

Increased sensitivity to ethanol in viral free rats compared to non-viral free rats of the same strain and supplier: a technical note

Adult viral free Sprague-Dawley rats were compared with non-viral free rats of the same strain and supplier for their sleep-time and hypothermic response to an acute injection of ethanol (3.5 g/kg, IP). Viral free animals were found to be significantly more sensitive to the sleep-time and hypothermic properties of ethanol than the non-viral free animals. This increased sensitivity was accompanied by higher blood alcohol concentrations in viral free animals for up to four hours after ethanol injection. These results indicate that animals born and raised in a viral free environment differ markedly in their sensitivity to ethanol compared to non-viral free animals derived from the same genetic stock. Such differences may be due to decreased metabolic clearance of ethanol in viral free animals. These findings suggest that the use of viral free animals in developmental, behavioral, pharmacological or toxicological studies of the effects of ethanol may be an important consideration.

Lack of prenatal testosterone surge in fetal rats exposed to alcohol: alterations in testicular morphology and physiology

Pregnant Sprague-Dawley rats were administered a liquid alcohol diet (35% ethanol-derived calories), a pair-fed isocaloric diet, or dry food pellets beginning on Day 14 of gestation and continuing until parturition. Testosterone levels in male fetuses were measured on Days 17 through 20 of gestation. The normal surge of testosterone on Days 18 and 19 was present in controls, but notably absent in male fetuses exposed to alcohol. Light microscopic examination of the testes at birth revealed a reduction in the number of leydig cells in the alcohol exposed group and the presence of a large number of vacuoles in the seminiferous tubules. In vitro studies of fetal testes at 18 and 22 days of gestation revealed that this in utero alcohol exposure regimen produced a marked insensitivity to rat LH (10 ng/ml) stimulation of testosterone secretion compared to controls. The response to ethanol (160 mg/dl) in alcohol exposed testes was characterized by a long-lasting suppression of testosterone compared to a large increase observed in control testes. No differences in anogenital distance were observed among the groups. Together, these data may explain some of the long-term feminizing and demasculinizing effects on reproductive and nonreproductive sexually dimorphic behaviors observed in adult males prenatally exposed to alcohol.

Neonatal exposure to a high level of ACTH4-10 impairs adult learning performance

Male offspring of Sprague-Dawley dams were injected with 25 micrograms of ACTH4-10 or the vehicle on days 2 through 7 postpartum. Peptide treated animals exhibited a marked motor response to the peptide injection. Adrenal weights of these animals were consistently heavier than littermate controls in both the developing and adult animals. ACTH4-10 treated neonates exhibited significantly poorer learning performance in the shuttle box and were slower to acquire the reversal learning problem of a visual discrimination task under light shock levels. In addition, these animals also exhibited an exaggerated startle response and a stronger thigmotaxis response in the open field than controls. These results indicate that exposing the developing nervous system to relatively high levels of ACTH4-10 can produce marked long-term effects on behavior.

Influence of prenatal exposure to cimetidine and alcohol on selected morphological parameters of sexual differentiation: a preliminary report

Pregnant rats were administered ethanol, cimetidine or a combination of both drugs from day 14 of gestation until parturition. Ano-genital (AG) distance measured at birth was significantly reduced in males exposed to cimetidine, but not in males or females exposed to alcohol. AG distance in males exposed to both ethanol and cimetidine also was not reduced, indicating a possible protective influence of ethanol against this effect of cimetidine. Birthweights in both sexes were reduced by prenatal ethanol exposure, both alone and with cimetidine exposure. Prenatal cimetidine exposure, both alone and in combination with ethanol significantly reduced seminal vesicle weights of adult males. However, no long-term effects of ethanol or cimetidine were observed on adrenal, testicular or ovarian weights. These results indicate that when fetal alcohol exposure is restricted to the critical prenatal period for hormonal actions on sexual differentiation, testosterone levels are maintained at an adequate level for normal morphological development of the genitalia.

Effects of prenatal testosterone propionate treatment on saccharin preference of adult rats exposed to ethanol in utero

Prenatal exposure to alcohol feminizes saccharin consumption patterns in adult male rats. To study the involvement of testosterone in this effect, testosterone propionate (TP) was administered to pregnant dams in an attempt to reverse that feminized saccharin consumption pattern in the male offspring. Female offspring were also studied to determine the effect of TP on saccharin preference in normal males and females. During the last week of gestation, dams were administered a liquid diet containing 35% ethanol derived calories, an isocaloric liquid diet containing no ethanol, or Purina Lab Chow. Half of the dams in each group received twice daily injections of TP, the other half were injected with the oil vehicle. Saccharin consumption of adult fetal alcohol exposed (FAE) males from dams administered oil or TP was significantly greater than controls, indicating that the feminized pattern of saccharin consumption of FAE males cannot be overcome with TP administration during the prenatal period. In controls, prenatal TP exposure alone was found to increase adult saccharin consumption in both sexes. Prenatal administration of TP was also found to markedly depress body weight of offspring of dams receiving the liquid diets compared to offspring from dams receiving the same diets plus oil injections. Body weights of offspring from TP or oil injected dams receiving the chow fed diets during pregnancy did not differ.

Influence of prenatal ethanol exposure on hormonal responses to clonidine and naloxone in prepubescent male and female rats

The expression of sexually dimorphic behavior has been found to be altered in adult animals following prenatal alcohol exposure. The present study examined whether such exposure would alter the sexually dimorphic response of luteinizing hormone (LH) to clonidine and naloxone observed in normal prepubescent animals. Both LH and corticosterone (CS) were measured in 16 day old male and female rats 30 min after injection of naloxone (2 mg/kg) or clonidine (0.1 mg/kg). Prenatal alcohol exposure did not influence the LH response to either drug in females. An LH response to clonidine in normal males did not occur, but it was present in the males exposed to alcohol in utero and in the pair-fed controls. Prenatal alcohol exposure influenced the CS response to both drugs. CS levels were depressed in the naloxone-treated males prenatally exposed to alcohol compared to their saline-injected counterparts. The CS levels of other groups following naloxone administration were unchanged compared to saline injection. Normal animals of both sexes exhibited an elevation in CS levels following clonidine. However, this stimulatory effect of clonidine on CS release was absent in both female and male animals prenatally exposed to alcohol. The results of this study indicate that prenatal alcohol exposure may alter noradrenergic and opioid modulation of corticosterone and possibly of LH in young animals.

Exposure to alcohol in utero alters the adult patterns of luteinizing hormone secretion in male and female rats

Luteinizing hormone (LH) secretory patterns were characterized in adult male and female rats exposed to ethanol during the last week of fetal life. Gonadectomized fetal alcohol exposed (FAE) males and females had significantly reduced plasma LH titers as compared to those of pair-fed (PF) controls. The phasic afternoon LH secretory response to estrogen and progesterone priming was also significantly reduced in FAE females. These differences do not appear to be a result of altered pituitary sensitivity to luteinizing hormone releasing hormone (LHRH), since the infusion of LHRH resulted in an equal response in PF and FAE females. Subsequent characterization of the episodic pattern of LH secretion in FAE males revealed significantly reduced mean LH level as well as a decreased pulse amplitude and frequency when compared to PF males. Taken together, these data indicate that some of the central mechanisms controlling pituitary LH secretion are altered by prenatal exposure to alcohol.

Prenatal alcohol exposure alters adult expression of sexually dimorphic behavior in the rat

Saccharin preference and performance in a Lashley III maze were found to be altered in adult male and female rats that had been exposed to alcohol during gestation. Specifically, the sexual dimorphism normally observed in both behaviors was absent in fetal alcohol-exposed animals. The lack of sexual dimorphism appeared to result from a masculinization of the exposed females and a feminization of the exposed males.

Prenatal alcohol exposure alters enkephalin levels, without affecting ethanol preference

Pregnant dams were pair-fed a liquid diet containing 35% ethanol derived calories or isocaloric sucrose during the last two trimesters of pregnancy. No differences were observed in adult ethanol preference between fetal alcohol exposed (FAE) animals and pair-fed controls. However, Met- and Leu-enkephalin levels were significantly elevated in globus pallidus of adult FAE animals. Pituitary levels were unaffected.

Prolonged intermittent footshock stress decreases Met and Leu enkephalin levels in brain with concomitant decreases in pain threshold

The influence of a 21 day intermittent footshock regimen upon enkephalin levels in brain and adrenals was examined in the rat. Changes in pain sensitivity as well as analgesic and hyperthermic responsiveness to morphine (7.5 mg/kg) were also monitored. Following the stress regimen, Met and Leu enkephalin levels were decreased by 40 to 50% in brain, but were unchanged in adrenals. Post-stress pain thresholds were markedly decreased in stressed animals while the analgesic properties of morphine were enhanced. Core body temperature of stressed animals was significantly raised, but the hyperthermic response to morphine was unchanged.

Mediation of diurnal fluctuations in pain sensitivity in the rat by food intake patterns: reversal by naloxone

Rats maintained on a 12-hour light-dark cycle were tested for pain sensitivity after being deprived of food during either the dark or the light phase of the cycle. Diurnal fluctuations in pain sensitivity were observed. The fluctuations followed food intake patterns rather than a natural circadian rhythm, with food deprivation producing a decrease in pain sensitivity. The analgesic response produced by this mild food deprivation was strongly attenuated by naloxone or feeding, suggesting that endogenous opioid systems may be related to patterns of food intake.