Central Actions of 3α,5α-THP Involving NMDA and GABAA Receptors Regulate Affective and Sexual Behavior of Female Rats.

The neurosteroid, 5α-pregnan-3α-ol-20-one (known as "allopregnanolone" or 3α,5α-THP), is produced in the midbrain ventral tegmental area (VTA), independent of peripheral sources of progestogens, where it has potential actions at N-methyl-D-aspartate (NMDA) and GABAA receptors to facilitate rodent sexual behavior. Progestogens can also have anti-anxiety effects, but whether these involve actions of centrally-derived 3α,5α-THP or these receptors to support reproductively-relevant behavior is not well understood. We investigated the extent to which 3α,5α-THP's actions via NMDA and/or GABAA receptors in the midbrain VTA influence reproductive behaviors. Estradiol-primed, ovariectomized/adrenalectomized (OVX/ADX) rats received midbrain VTA infusions of vehicle, an NMDA receptor blocker (MK-801; 200 ng), or a GABAA receptor blocker (bicuculline; 100 ng) followed by a second infusion of vehicle or 3α,5α-THP (100 ng). Reproductively-relevant behaviors were assessed: sexual (paced mating), anxiety-like (elevated plus maze), and social (partner preference, social interaction) behavior. Compared to vehicle, intra-VTA infusions of MK-801 exerted anxiolytic-like effects on elevated plus maze behavior and enhanced lordosis. Unlike prior observations in gonadally-intact rats, intra-VTA bicuculline had no effect on the behavior of OVX/ADX rats (likely due to a floor effect). Subsequent infusions of 3α,5α-THP reversed effects on lordosis and infusions of bicuculline inhibited 3α,5α-THP-facilitated lordosis. Thus, NMDA and GABAA receptors may act as mediators for reproductive behavioral effects of 3α,5α-THP in the midbrain VTA.

Progesterone's Effects on Cognitive Performance of Male Mice Are Independent of Progestin Receptors but Relate to Increases in GABAA Activity in the Hippocampus and Cortex.

Progestogens' (e.g., progesterone and its neuroactive metabolite, allopregnanolone), cognitive effects and mechanisms among males are not well-understood. We hypothesized if progestogen's effects on cognitive performance are through its metabolite allopregnanolone, and not actions via binding to traditional progestin receptors (PRs), then progesterone administration would enhance performance in tasks mediated by the hippocampus and cortex, coincident with increasing allopregnanolone concentrations, brain derived neurotrophic factor (BDNF) and/or muscimol binding of PR knock out (PRKO) and wild-type PR replete mice. Experiment 1: Progesterone (4 mg/kg, subcutaneously (SC; n = 12/grp), or oil vehicle control, was administered to gonadally-intact adult male mice PRKO mice and their wild-type counterparts and cognitive behaviors in object recognition, T-maze and water maze was examined. Progesterone, compared to vehicle, when administered post-training increased time investigating novel objects by the PRKO and wild-type mice in the object recognition task. In the T-maze task, progesterone administration to wild-type and PRKO mice had significantly greater number of spontaneous alternations compared to their vehicle-administered counterparts. In the water maze task, PRKO mice administered vehicle spent significantly fewer seconds in the quadrant associated with the escape platform on testing compared to all other groups. Experiment 2: Progesterone administered to wild-type and PRKO mice increased plasma progesterone and allopregnanolone levels (n = 5/group). PRKO mice had higher allopregnanolone levels in plasma and hippocampus, but not cortex, when administered progesterone and compared to wild-type mice. Experiment 3: Assessment of PR binding revealed progesterone administered wild-type mice had significantly greater levels of PRs in the hippocampus and cortex, compared to all other groups (n = 5/group). Wild-type mice administered progesterone, but not vehicle, had increased BDNF levels in the hippocampus, but not the cortex, compared to PRKOs. Wild-type as well as PRKO mice administered progesterone experienced significant increases in maximal GABAA agonist, muscimol, binding in hippocampus and cortex, compared to their vehicle-administered counterparts. Thus, adult male mice can be responsive to progesterone for cognitive performance, and such effects may be independent of PRs trophic actions of BDNF levels in the hippocampus and/or increases in GABAA activity in the hippocampus and cortex.

Effects of non-contingent cocaine on 3alpha-androstanediol. I. Disruption of male sexual behavior.

One of the hallmarks of drug abuse is a reduction in the salience of, and motivation for, natural rewards, such as mating. The effects of psychostimulants on male sexual interest and performance are conflicting; use of psychostimulants can produce increases in risky sexual behaviors but have detrimental effects on sexual ability. We hypothesize that these conflicting effects on sexual behavior are due to interactions between cocaine and androgens, such as testosterone and its neuroactive metabolite, 3α-androstanediol (3α-diol). Male rats were administered saline or cocaine (5, 10, or 20mg/kg, i.p.). Motor behavior was observed in the first 30min following drug-administration, and then sexual responding was assessed for 15min. Levels of androgens (testosterone, 3ɑ-diol, and testosterone's aromatized metabolite, estradiol) were measured in circulation and brain regions (frontal cortex, hippocampus, hypothalamus/striatum (hypo/str), and midbrain). Cocaine had no effect on measures of sexual interest (i.e. anogenital investigation). However, cocaine had substantial effects on consummatory sexual behaviors, such as the latency to mount/intromit and the number of sexual contacts. Frontal cortex and hypo/str 3α-diol levels were strongly correlated with consummatory behaviors in saline administered rats; however, this relationship was disrupted by cocaine at all dosages, concomitant with impaired sexual behaviors. Additionally, there was a shift in metabolism at low dosages of cocaine to push testosterone metabolism in the midbrain towards 3α-diol. On the contrary, moderate and high dosages of cocaine shifted testosterone metabolism towards estradiol. These data demonstrate that the association between cortical and hypo/str 3α-diol levels and sexual behavior of male rats is disrupted by non-contingent cocaine and that there may be dose-dependent effects of acute cocaine on androgen metabolism.

Effects of non-contingent cocaine on 3 alpha-androstanediol. II. Disruption of lordosis of proestrous rats.

Drug use influences sexual behavior, performance, and can be associated with increased sexual risk-taking. Our prior results using an animal model indicate that progestogens contribute to hormonally-mediated changes in sexual behavior of female rodents during acute cocaine exposure. Androgens, such as testosterone, and its metabolite 3ɑ-androstanediol (3α-diol), and estradiol, are known to influence male sexual behavior, but can also alter the expression of sexual behavior of female rodents. As such, we investigated the influence of endogenous androgen and estradiol fluctuations on cocaine-mediated changes in motor behavior and sexual receptivity of rats during diestrous or proestrous phases of the estrous cycle. Female rats were administered saline or cocaine (5, 10, or 20mg/kg, i.p.). Motor behavior was observed in the first 30min following drug administration, and then sexual responding was assessed for 15min. Cocaine decreased aggressive behavior in response to attempted mounts by a male among non-receptive (diestrous) rats and inhibited sexual behavior among sexually receptive (proestrous) rats. Cocaine dose-dependently altered concentrations of testosterone metabolites (estradiol and 3α-diol), but not testosterone, which correlated to motor and sexual behaviors of diestrous and proestrous rats, respectively. These data suggest that actions of 3α-diol may be involved in female sexual and motor behavior in response to cocaine, in a cycle-dependent manner.

Research Brief: Self-Reports of a Constellation of Persistent Antiandrogenic, Estrogenic, Physical, and Psychological Effects of Finasteride Usage Among Men.

Our research objective is to understand more, through subjective, self-reports on discussion boards/forums, persons' experiences associated with the use of drugs that alter androgen metabolism, such as finasteride. Finasteride is an orally active, specific inhibitor of 5α-reductase, which is localized to many androgen-dependent tissues. Finasteride inhibits the conversion of testosterone (T) to dihydrotestosterone (DHT), and is commonly used to treat benign prostatic hypertrophy (BPH) and male pattern baldness (MPB), both disorders associated with elevated DHT levels and 5α-reductase activity in the prostate and hair follicles, respectively. It is now acknowledged that long-term use and discontinuation of finasteride has adverse effects (AEs); however, these claims have not been well documented. In this study, discussion board posts (forums) were analyzed as self-reports of what finasteride users indicate is problematic for them. Reports were categorized by the age of subjects as well as the types of AEs described: antiandrogenic, estrogenic, central, and nonspecific/severe. A total of 244 cases were recorded and analyzed on the discussion forum on propeciahelp.com . Among these, 74 (32%) cases reported antiandrogenic affects, 43 (19%) reported estrogenic effects, 70 (30%) reported central effects, 11 (5%) reported nonspecific/severe AEs, and 31 (14%) reported AEs in all categories. The categorization of AEs may prompt further investigation into the pathophysiology of post-finasteride syndrome (PFS). Also, subjective reports may engender greater understanding of the perceived lasting AEs of finasteride.

Progestogens' effects and mechanisms for object recognition memory across the lifespan.

This review explores the effects of female reproductive hormones, estrogens and progestogens, with a focus on progesterone and allopregnanolone, on object memory. Progesterone and its metabolites, in particular allopregnanolone, exert various effects on both cognitive and non-mnemonic functions in females. The well-known object recognition task is a valuable experimental paradigm that can be used to determine the effects and mechanisms of progestogens for mnemonic effects across the lifespan, which will be discussed herein. In this task there is little test-decay when different objects are used as targets and baseline valance for objects is controlled. This allows repeated testing, within-subjects designs, and longitudinal assessments, which aid understanding of changes in hormonal milieu. Objects are not aversive or food-based, which are hormone-sensitive factors. This review focuses on published data from our laboratory, and others, using the object recognition task in rodents to assess the role and mechanisms of progestogens throughout the lifespan. Improvements in object recognition performance of rodents are often associated with higher hormone levels in the hippocampus and prefrontal cortex during natural cycles, with hormone replacement following ovariectomy in young animals, or with aging. The capacity for reversal of age- and reproductive senescence-related decline in cognitive performance, and changes in neural plasticity that may be dissociated from peripheral effects with such decline, are discussed. The focus here will be on the effects of brain-derived factors, such as the neurosteroid, allopregnanolone, and other hormones, for enhancing object recognition across the lifespan.

Allopregnanolone levels and seizure frequency in progesterone-treated women with epilepsy.

OBJECTIVE: To determine whether allopregnanolone (AP) may mediate seizure reduction in progesterone-treated women with epilepsy. METHODS: The NIH Progesterone Trial compared the efficacy of adjunctive cyclic natural progesterone therapy vs placebo treatment of intractable seizures in 294 subjects, randomized 2:1 to progesterone or placebo, stratified by catamenial vs noncatamenial designation. Treatments were compared on proportions of 50% responders, and changes in seizure frequency from 3 baseline to 3 treatment cycles. Serum AP levels were measured by radioimmunoassay from 155 women with intractable focal-onset seizures who had baseline and treatment-phase midluteal serum samples drawn each cycle for hormone measurements. RESULTS: There was no significant correlation between percentage changes in AP levels and seizure frequencies from baseline to treatment for either the catamenial or noncatamenial stratum. There was a significant correlation for the subset of subjects who showed a significantly greater responder rate in the post hoc analysis of the trial, i.e., subjects who had a 3-fold or greater increase in average daily seizure frequency perimenstrually compared with the midfollicular and midluteal phases (C1 ≥ 3: r = -0.442, p = 0.013, and specifically for C1 ≥ 3 progesterone-treated subjects [r = -0.452, p = 0.035], but not other groups [C1 ≥ 3 placebo: r = -0.367; C1 <3 progesterone: r = 0.099; C1 <3 placebo: r = 0.131; p = not significant]). CONCLUSIONS: The findings support AP as a mediator of seizure reduction in progesterone-treated women who have a substantial level of perimenstrually exacerbated seizures.

Female mice with deletion of Type One 5α-reductase have reduced reproductive responding during proestrus and after hormone-priming.

The capacity to form progesterone (P4)'s 5α-reduced metabolite, 5α-pregnan-3α-ol-20-one (3α,5α-THP; a.k.a. allopregnanolone), in the brain may be related to facilitation of lordosis among estrogen-primed (E2) mice. We investigated this idea further by comparing effects of endogenous and exogenous progestogens in mice that are deficient in the Type One 5α-reductase enzyme (5α-reductase knockout mice; 5α-RKO), and their wildtype counterparts for sexual behavior. Comparisons were made following administration of progestogens that are expected to increase 3α,5α-THP or not. Sexual receptivity of 5α-RKO mice and their wildtype counterparts was examined when mice were naturally-cycling (Experiment 1); ovariectomized (OVX), E2-primed (10 µg, subcutaneous; SC) and administered P4 (0, 125, 250, or 500 µg SC; Experiment 2); and OVX, E2-primed and administered P4, medroxyprogesterone acetate (MPA, 4 mg/kg, SC, which does not convert to 3α,5α-THP) or 3α,5α-THP (4 mg/kg, SC; Experiment 3). The percentage of mounts that elicited lordosis (lordosis quotient) or aggression/rejection behavior (aggression quotient), as well as the quality of lordosis (lordosis rating), was scored. Wildtype, but not 5α-RKO, mice in behavioral estrus demonstrated significantly greater lordosis quotients and lordosis ratings, but similar aggression quotients, compared to their diestrous counterparts. Among OVX and E2-primed mice, P4 facilitated lordosis of wildtype, but not 5α-RKO, mice. MPA neither facilitated lordosis of wildtype, nor 5α-RKO mice. 3α,5α-THP administered to wildtype or 5α-RKO mice increased lordosis quotients and lordosis ratings and decreased aggression quotients. 3α,5α-THP levels in the midbrain, one brain region important for sexual behavior, were increased during behavioral estrus, with P4 administered to WT, but not 5α-RKO mice, and 3α,5α-THP administered to WT and 5α-RKO mice. MPA did not increase 3α,5α-THP. Thus, deletion of Type One 5α-reductase among female mice may attenuate reproductive responding during the estrous cycle and after hormone-priming.

Endocrine-disrupting chemicals: elucidating our understanding of their role in sex and gender-relevant end points.

Endocrine-disrupting chemicals (EDCs) are diverse and pervasive and may have significant consequence for health, including reproductive development and expression of sex-/gender-sensitive parameters. This review chapter discusses what is known about common EDCs and their effects on reproductively relevant end points. It is proposed that one way that EDCs may exert such effects is by altering steroid levels (androgens or 17-estradiol, E2) and/or intracellular E2 receptors (ERs) in the hypothalamus and/or hippocampus. Basic research findings that demonstrate developmentally sensitive end points to androgens and E2 are provided. Furthermore, an approach is suggested to examine differences in EDCs that diverge in their actions at ERs to elucidate their role in sex-/gender-sensitive parameters.

Progesterone-facilitated lordosis of estradiol-primed mice is attenuated by knocking down expression of membrane progestin receptors in the midbrain.

Evidence is emerging of the role of membrane progestin receptors (referred to as mPRs herein: members of Progestin and AdipoQ Receptor (Paqr) family) as a novel brain target in mammals, such as rats. In the present study, the role of mPRs in mice was assessed to further elucidate the conservation of this mechanism across species. The brain target investigated was the midbrain ventral tegmental area (VTA) given its described role for rapid actions of progestins for reproduction. Studies tested the hypothesis that if mPRs are required for progestin-facilitated lordosis through actions in the VTA, then knockdown of mPRs in the VTA will attenuate lordosis. Ovariectomized (OVX) mice were subcutaneously injected with estradiol (E2) and progesterone (P4), and infused with antisense oligodeoxynucleotides (AS-ODNs) to mPRα (Paqr7) and/or mPRß (Paqr8) or vehicle to the lateral ventricle or VTA. Mice were assessed for reproductive behavior (lordosis and aggression/rejection quotients) in a standard mating task. Results supported our hypothesis. E2+P4-facilitated lordosis was significantly reduced, and aggression/rejection increased, with infusions of mPRα, mPRß, or mPRαß AS-ODNs to the lateral ventricle, compared to vehicle. E2+P4-facilitated lordosis was significantly decreased, and aggression/rejection increased, with mPRß or mPRαß AS-ODNs to the VTA of C57/BL6 mice. Both mPRɑ and mPRß AS-ODNs reduced lordosis, and increased aggression/rejection, of wildtype (C57/BL6x129) mice, but not nuclear PR knockout mice. Thus, mPRs may be a novel target of progestins for reproductive behavior of mice.

Progesterone facilitates exploration, affective and social behaviors among wildtype, but not 5α-reductase Type 1 mutant, mice.

Progesterone (P4) facilitates exploration, anxiety and social behaviors in estrogen (E2)-primed mice. Some of these effects may be due to actions of its 5α-reduced metabolite, 5α-pregnan-3α-ol-20-one (3α,5α-THP). In order to address the role of P4 and its metabolite, 3α,5α-THP, a mouse model was utilized. We hypothesized that if P4's metabolism to 3α,5α-THP is essential to facilitate exploratory, anti-anxiety and social behaviors of mice, then wildtype, but not 5α-reductase knockout (5α-RKO), mice will have greater expression of these behaviors. Experiment 1: Mice were ovariectomized (ovx), E2-primed and administered P4 (0, 125, 250, or 500µg) subcutaneously and then tested 4h later in a battery of tasks: open field, elevated plus maze, and social interaction. Experiment 2: Ovx, E2-primed mice were administered P4 (4mg/kg), 3α,5α-THP (4mg/kg), medroxyprogesterone acetate (MPA, which does not convert to 3α,5α-THP; 4mg/kg), or vehicle subcutaneously and tested 4h later. There was a dose-dependent effect of P4 to wildtype, but not 5α-RKO, mice. Neither wildtype, nor 5α-RKO, mice had increased exploration, anti-anxiety or pro-social behavior with MPA administration. Progesterone only exerted effects on anti-anxiety behavior, and increased 3α,5α-THP in the prefrontal cortex and hippocampus, when administered to wildtype mice. 3α,5α-THP to both WT and 5α-RKO mice increased exploration, anti-anxiety and social interaction and 3α,5α-THP levels in the hippocampus and prefrontal cortex. Thus, metabolism of P4 by the 5α-reductase enzyme may be essential for enhancement of these behaviors.

Progesterone, compared to medroxyprogesterone acetate, to C57BL/6, but not 5α-reductase mutant, mice enhances object recognition and placement memory and is associated with higher BDNF levels in the hippocampus and cortex.

Progesterone (P4) may influence cognition in part through actions of its 5α-reduced metabolite, allopregnanolone. Ovariectomized mice that were C57BL/6 wildtype (WT), or deficient in the 5α-reductase Type 1 enzyme (5α-reductase knockout; 5αRKO), were administered vehicle, P4, allopregnanolone, or medroxyprogesterone acetate (MPA) after training in the object recognition or placement tasks. WT mice administered P4 or allopregnanolone performed significantly better in the object recognition and placement tasks than did WT mice administered vehicle or MPA. 5αRKO mice administered allopregnanolone, but not P4, MPA, or vehicle showed enhanced performance in the object recognition and placement tasks. Levels of brain-derived neurotrophic factor (BDNF) in the prefrontal cortex and hippocampus were lowest among mice administered MPA. Thus, some of P4s effects to enhance cognitive performance may be incumbent upon its 5α-reduction.

Membrane progestin receptors in the midbrain ventral tegmental area are required for progesterone-facilitated lordosis of rats.

Progesterone (P4) and its metabolites, rapidly facilitate lordosis of rats partly through actions in the ventral tegmental area (VTA). The study of membrane progestin receptors (mPRs), of the Progestin and AdipoQ Receptor (PAQR) superfamily, has been limited to expression and regulation, instead of function. We hypothesized that if mPRs are required for progestin-facilitated lordosis in the VTA, then mPRs will be expressed in this region and knockdown will attenuate lordosis. First, expression of mPR was examined by reverse-transcriptase polymerase chain reaction (RT-PCR) in brain and peripheral tissues of proestrous Long-Evans rats. Expression of mPRα (paqr7) was observed in peripheral tissues and brain areas, including hypothalamus and midbrain. Expression of mPRß (paqr8) was observed in brain tissues and was abundant in the midbrain and hypothalamus. Second, ovariectomized rats were estrogen (E2; 0.09 mg/kg, SC), and P4 (4 mg/kg, SC) or vehicle-primed, and infused with antisense oligodeoxynucleotides (AS-ODNs) targeted against mPRα and/or mPRß intracerebroventricularly or to the VTA. Rats were assessed for motor (open field), anxiety (elevated plus maze), social (social interaction), and sexual (lordosis) behavior. P4-facilitated lordosis was significantly reduced with administration of AS-ODNs for mPRα, mPRß, or co-administration of mPRα and mPRß to the lateral ventricle, compared to vehicle. P4-facilitated lordosis was reduced, compared to vehicle, by administration of mPRß AS-ODNs, or co-administration of mPRα and mPRß AS-ODNs, but not mPRα AS-ODNs alone, to the VTA. No differences were observed for motor, anxiety, or social behaviors. Thus, mPRs in the VTA are targets of progestin-facilitated lordosis of rats.

Type 1 5α-reductase may be required for estrous cycle changes in affective behaviors of female mice.

There are estrous cycle differences in affective behaviors of rodents that are generally attributed to cyclic variations in estradiol, progesterone (P) and its metabolites. A question is the role of the steroid metabolism enzyme, 5α-reductase, for these estrous cycle differences. To address the requirement of 5α-reductase, estrous cycle variations in the behavior of wildtype mice and their littermates that are deficient in the 5α-reductase type 1 enzyme (5αRKO mice) were examined. The hypothesis was that if some of the estrous cycle differences in exploratory (open field) and anxiety (elevated plus maze) are due to P's 5α-reduction to 5α-pregnan-3α-ol-20-one (3α,5α-THP), then wildtype mice will have estrous cycle differences in the expression of these behaviors, but 5αRKO mice will not. Mice were tested in these tasks and then had plasma and brains collected so that steroid levels (estradiol, P, 3α,5α-THP, corticosterone) could be measured in these tissues. Results supported this hypothesis. There were estrous cycle differences among wildtype, but not 5αRKO, mice. Proestrous wildtype mice made more central entries in the open field and spent more time on the open arms of the plus maze, coincident with higher 3α,5α-THP levels in plasma and brain regions important for these behaviors, such as the hippocampus and cortex, compared to their diestrous counterparts. Variability in the open field and elevated plus maze could be explained by circulating and hippocampus levels of 3α,5α-THP, respectively. Thus, 5α-reductase may be required for the estrous cycle variations in affective behavior and 3α,5α-THP levels of female mice.

Immune stress in late pregnant rats decreases length of gestation and fecundity, and alters later cognitive and affective behaviour of surviving pre-adolescent offspring.

Immune challenge during pregnancy is associated with preterm birth and poor perinatal development. The mechanisms of these effects are not known. 5α-Pregnan-3α-ol-20-one (3α,5α-THP), the neuroactive metabolite of progesterone, is critical for neurodevelopment and stress responses, and can influence cognition and affective behaviours. To develop an immune challenge model of preterm birth, pregnant Long-Evans rat dams were administered lipopolysaccharide [LPS; 30 µg/kg/ml, intraperitoneal (IP)], interleukin-1ß (IL-1ß; 1 µg/rat, IP) or vehicle (0.9% saline, IP) daily on gestational days 17-21. Compared to control treatment, prenatal LPS or IL-1ß reduced gestational length and the number of viable pups born. At 28-30 days of age, male and female offspring of mothers exposed to prenatal IL-1ß had reduced cognitive performance in the object recognition task compared to controls. In females, but not males, prenatal IL-1ß reduced anxiety-like behaviour, indicated by entries to the centre of an open field. In the hippocampus, progesterone turnover to its 5α-reduced metabolites was lower in prenatally exposed IL-1ß female, but not in male offspring. IL-1ß-exposed males and females had reduced oestradiol content in hippocampus, medial prefrontal cortex and diencephalon compared to controls. Thus, immune stress during late pregnancy reduced gestational length and negatively impacted birth outcomes, hippocampal function and central neurosteroid formation in the offspring.

Progesterone attenuates depressive behavior of younger and older adult C57/BL6, wildtype, and progesterone receptor knockout mice.

Progesterone may have actions independent of intracellular progestin receptors (PRs) to influence depressive behavior. To investigate this, we examined effects of progesterone (P; 10mg/kg, SC) on the depressive behavior of mice in the forced swim test (FST). In Experiment 1, subjects were 4 to 6 months old, intact or ovariectomized (OVX) female and intact or gonadectomized (GDX) male, C57/BL6 mice. Progesterone reduced depressive behavior of young diestrous and OVX mice but male mice were impervious to effects of P. In Experiment 2, subjects were intact aged (20-28 months old) C57/BL6 female and male mice. Progesterone reduced depressive behavior of aged female and male C57/BL6 mice, albeit effects were greater among males. In Experiment 3, effects of P were examined in 4 to 6 months old, gonadally-intact, female and male mice that were wildtype or PR knockouts (PRKOs). Progesterone decreased depressive behavior of young adult, wildtype and PRKO mice, which showed greater immobility than did their wildtype counterparts. In Experiment 4, subjects were 18-24 months old wildtype or PRKO mice (Exp 4). Progesterone decreased immobility among wildtype and PRKO mice (which were not different in terms of their baseline depressive behavior). Together these data demonstrate that P decreases depressive behavior of young and older adult C57/BL6, wildtype and PRKO mice, which suggest that acute anti-depressant effects of P may occur independent of actions at "classic" PRs.

Effects of neurosteroid actions at N-methyl-D-aspartate and GABA A receptors in the midbrain ventral tegmental area for anxiety-like and mating behavior of female rats.

RATIONALE: In the midbrain ventral tegmental area (VTA), actions of neurosteroids, such as the progesterone metabolite, 5α-pregnan-3α-ol-20-one (3α,5α-THP), can facilitate mating and influence stress-related processes. Some actions of 3α,5α-THP may occur via positive modulation of GABA(A) receptors (GBRs), or negative modulation of N-methyl-D: -aspartate receptors (NMDARs), to influence anxiety-like behavior; but this is not known. OBJECTIVES: We aimed to assess the role that neurosteroids and stress factors play on intra-VTA NMDAR- and/or GBR-mediated anxiety-like and mating behavior. METHODS: Estradiol-primed, ovariectomized rats, which were partially or completely adrenalectomized (ADX), received infusions of vehicle, an NMDAR blocker (MK-801; 200 ng), or a GBR antagonist (bicuculline, 100 ng) to the VTA. Rats then received intra-VTA vehicle or a neurosteroidogenesis enhancer (N,N-Dihexyl-2-(4-fluorophenyl)indole-3-acetamide, FGIN 1-27, 5 µg) and anxiety-like and sexual behavior was assessed. RESULTS: Complete, compared to partial, ADX significantly reduced open arm exploration on an elevated plus maze, the proportion of females that engaged in mating, lordosis quotients, pacing of sexual contacts, and defensive aggression towards a sexually vigorous male. Intra-VTA MK-801 enhanced open arm investigation and the proportion of females that engaged in mating. Infusions of either, MK-801 or FGIN 1-27, enhanced lordosis and, when co-administered, FGIN 1-27 attenuated MK-801's lordosis-enhancing effects. Intra-VTA infusions of bicuculline, prior to FGIN 1-27, blocked FGIN 1-27's effects to enhance lordosis. CONCLUSIONS: Together, these data suggest that reduced NMDAR activity in the VTA may influence motivation to explore and engage in sexual behavior. These data suggest that neurosteroid actions at NMDARs and GBRs in the VTA are important for exploration and/or sexual behavior.

Progesterone, administered before kainic acid, prevents decrements in cognitive performance in the Morris Water Maze.

The nature of progesterone (P4)'s neuroprotective effects is of interest. We investigated effects of P4 when administered before, or after, kainic acid, which produces ictal activity and damage to the hippocampus, to mediate effects on spatial performance. The hypothesis was that P4, compared with vehicle, would reduce decrements in Morris Water Maze performance induced by kainic acid. Experiment 1: We examined the effects of kainic acid on plasma stress hormone, corticosterone, and progestogen (P4 and its metabolites) levels in plasma and the hippocampus after subcutaneous (s.c.) P4 administration to ovariectomized rats. Rats administered kainic acid had the highest corticosterone levels immediately following injection. P4 is 5α-reduced to dihydroprogesterone (DHP) and subsequently metabolized to 5α-pregnan-3α-ol-20-one (3α,5α-THP) by 3α-hydroxysteroid dehydrogenase. The regimen of P4 used produced circulating and hippocampal levels of P4, DHP, and 3α,5α-THP within a physiological range, which declined at 14 hours postinjection and were not altered by kainic acid. Experiment 2: The physiological P4 regimen was administered to rats before, or after, kainic acid-induced seizures, and later effects on water maze performance were compared with that of rats administered vehicle. Rats administered kainic acid had significantly poorer performance in the water maze (i.e., increased latencies and distances to the hidden platform) than did rats administered vehicle. Administration of P4 before, but not after, kainic acid prevented these performance deficits. Thus, these data suggest that a physiological regimen of P4 can prevent some of the deficits in water maze performance produced by kainic acid.

Progesterone reduces depressive behavior of young ovariectomized, aged progestin receptor knockout, and aged wild type mice in the tail suspension test.

Progestins may have effects to reduce depressive behavior, in part through actions of its metabolite, 5α-pregnan-3α-ol-20-one (3α,5α-THP) at GABA(A) receptors, rather than through intracellular progestin receptors. In this study, we examined the effects of progesterone (10 mg/kg, subcutaneous injection) versus vehicle control (propylene glycol) on the depressive behavior of young and aged mice in the tail suspension test. In Experiment 1, we first characterized progesterone's anti-depressant effects by utilizing young (4-6-month-old) intact or ovariectomized female, and intact or gonadectomized male, C57BL/6 mice. Young female mice showed more depressive behavior than the young male mice. Compared with vehicle administration, progesterone reduced depressive behavior of ovariectomized female, but not male or intact female mice. In Experiment 2, mice were aged (20-24-month-old) intact wild type or progestin receptor knockout mice. Progestin receptor knockout mice showed less depressive behavior than wild type mice. Administration of progesterone to wild type and progestin receptor knockout mice reduced depressive behavior. Together, these data suggest that progesterone can decrease depressive behavior of young adult ovariectomized female, aged wild type and progestin receptor knockout mice. Thus, progesterone's effect to reduce depressive behavior of aged mice may not require actions at the intracellular progestin receptors.

Juvenile offspring of rats exposed to restraint stress in late gestation have impaired cognitive performance and dysregulated progestogen formation.

Gestational stress may have lasting effects on the physical and neurocognitive development of offspring. The mechanisms that may underlie these effects are of interest. Progesterone and its 5α-reduced metabolites, dihydroprogesterone and 5α-pregnan-3α-ol-20-one (3α,5α-THP), maintain pregnancy, have neurotrophic effects, and can enhance cognitive performance. We hypothesized that some of the deleterious effects of gestational stress on the cognitive performance of offspring may be related to progestogen formation. Pregnant rat dams were exposed to restraint under a bright light (thrice daily for 45 min) on gestational days 17-21 or were minimally handled controls. Dams that were exposed to restraint had lower circulating levels of 3α,5α-THP and significantly greater concentrations of corticosterone at the time of birth than did control dams. Male and female offspring, that were gestationally stressed or not, were cross-fostered to non-manipulated dams. Between postnatal days 28-30, offspring were assessed for object recognition, a prefrontal cortex (PFC)-dependent cognitive task. Restraint-exposed offspring performed more poorly in the object recognition task than did control offspring, irrespective of sex. As well, progesterone turnover to its 5α-reduced metabolites in the medial PFC (but not the diencephalon) was significantly reduced among restraint-exposed, compared to control, offspring. Progesterone turnover, and levels of 3α,5α-THP, positively correlated with performance in the object recognition task. Thus, restraint stress in late pregnancy impaired cognitive development and dysregulated progestogen formation in brain.