Radioimmunoassay of 3 alpha-hydroxy-5 alpha-pregnan-20-one in rat and human plasma

Neuroactive Steroids, Toll-like Receptors, and Neuroimmune Regulation: Insights into Their Impact on Neuropsychiatric Disorders

Pregnane neuroactive steroids, notably allopregnanolone and pregnenolone, exhibit efficacy in mitigating inflammatory signals triggered by toll-like receptor (TLR) activation, thus attenuating the production of inflammatory factors. Clinical studies highlight their therapeutic potential, particularly in conditions like postpartum depression (PPD), where the FDA-approved compound brexanolone, an intravenous formulation of allopregnanolone, effectively suppresses TLR-mediated inflammatory pathways, predicting symptom improvement. Additionally, pregnane neurosteroids exhibit trophic and anti-inflammatory properties, stimulating the production of vital trophic proteins and anti-inflammatory factors. Androstane neuroactive steroids, including estrogens and androgens, along with dehydroepiandrosterone (DHEA), display diverse effects on TLR expression and activation. Notably, androstenediol (ADIOL), an androstane neurosteroid, emerges as a potent anti-inflammatory agent, promising for therapeutic interventions. The dysregulation of immune responses via TLR signaling alongside reduced levels of endogenous neurosteroids significantly contributes to symptom severity across various neuropsychiatric disorders. Neuroactive steroids, such as allopregnanolone, demonstrate efficacy in alleviating symptoms of various neuropsychiatric disorders and modulating neuroimmune responses, offering potential intervention avenues. This review emphasizes the significant therapeutic potential of neuroactive steroids in modulating TLR signaling pathways, particularly in addressing inflammatory processes associated with neuropsychiatric disorders. It advances our understanding of the complex interplay between neuroactive steroids and immune responses, paving the way for personalized treatment strategies tailored to individual needs and providing insights for future research aimed at unraveling the intricacies of neuropsychiatric disorders.

Increased Voluntary Alcohol Consumption in Mice Lacking GABAB(1) Is Associated With Functional Changes in Hippocampal GABAA Receptors

Gamma-aminobutyric acid type B receptor (GABA_BR) has been extensively involved in alcohol use disorders; however, the mechanisms by which this receptor modulates alcohol drinking behavior remain murky. In this study, we investigate alcohol consumption and preference in mice lacking functional GABA_BR using the 2-bottle choice paradigm. We found that GABA_B(1), knockout (KO), and heterozygous (HZ) mice drank higher amounts of an alcoholic solution, preferred alcohol to water, and reached higher blood alcohol concentrations (BACs) compared to wild-type (WT) littermates. The GABA_BR agonist GHB significantly reduced alcohol consumption in the GABA_B(1) HZ and WT but not in the KO mice. Next, because of a functional crosstalk between GABA_BR and δ-containing GABA_A receptor (δ-GABA_AR), we profiled δ subunit mRNA expression levels in brain regions in which the crosstalk was characterized. We found a loss of the alcohol-sensitive GABA_AR δ subunit in the hippocampus of the GABA_B(1) KO alcohol-naïve mice that was associated with increased ɣ² subunit abundance. Electrophysiological recordings revealed that these molecular changes were associated with increased phasic inhibition, suggesting a potential gain of synaptic GABA_AR responsiveness to alcohol that has been previously described in an animal model of excessive alcohol drinking. Interestingly, voluntary alcohol consumption did not revert the dramatic loss of hippocampal δ-GABA_AR occurring in the GABA_B(1) KO mice but rather exacerbated this condition. Finally, we profiled hippocampal neuroactive steroids levels following acute alcohols administration in the GABA_B(1) KO and WT mice because of previous involvement of GABA_BR in the regulation of cerebral levels of these compounds. We found that systemic administration of alcohol (1.5 g/kg) did not produce alcohol-induced neurosteroid response in the GABA_B(1) KO mice but elicited an expected increase in the hippocampal level of progesterone and 3α,5α-THP in the WT controls. In conclusion, we show that genetic ablation of the GABA_B(1) subunit results in increased alcohol consumption and preference that were associated with functional changes in hippocampal GABA_AR, suggesting a potential mechanism by which preference for alcohol consumption is maintained in the GABA_B(1) KO mice. In addition, we documented that GABA_B(1) deficiency results in lack of alcohol-induced neurosteroids, and we discussed the potential implications of this finding in the context of alcohol drinking and dependence.

Effect of progesterone and first evidence about allopregnanolone action on the progression of epithelial human ovarian cancer cell lines

Ovarian carcinoma is one of the most common cause of death by gynecologic cancer. Several epidemiological and in vitro studies have shown controversial data about progesterone effects in ovarian cancer. Progesterone can be converted in its active metabolite, allopregnanolone, its effects in ovarian cancer are still unknown. Previously, we demonstrated that allopregnanolone modifies ovarian morphophysiology, being able to alter critical process of tumor development such as proliferation, apoptosis and angiogenesis. Taking into account these antecedents, we investigated the effect of progesterone and allopregnanolone on proliferation, apoptosis, clonogenic capacity and migration on two epithelial human ovarian cancer cell lines, IGROV-1 and SKOV-3. To this end, IGROV-1 and SKOV-3 cells were exposed to a range of progesterone and allopregnanolone concentrations (10^-11 to 10^-5 M) for 72 h. Proliferation was analyzed by MTT and Ki67 expression. Apoptosis was measured by immunocytochemistry of cleaved caspase 3. Clonogenic capacity was evaluated by counting colonies. Migration was analyzed by wound assay. We found that allopregnanolone increased proliferation and Ki67 expression respect to control on IGROV-1 cells, while expression of cleaved caspase 3 did not change in any cell line studied. IGROV-1 clonogenic capacity was also increased by allopregnanolone treatment. Both steroids, progesterone and allopregnanolone, increased IGROV-1 migration in a concentration dependent manner. None of the steroids tested modified SKOV-3 biological behavior analized. This is the first evidence that allopregnanolone, a progesterone metabolite, affects critical events in tumor development of human epithelial ovarian cancer. These results could have an impact in the future in clinic diagnosis, prognosis and treatment of ovarian cancer patients. The regulation of progesterone and allopregnanolone steroideogenesis and their molecular mechanisms might be considered as potential therapeutic tool in ovarian cancer.

Combined effect of gestational stress and postpartum stress on maternal care in rats

Variations in maternal care in the rat influence the development of individual differences in behavioral and endocrine responses to stress. This study aimed to examine the interaction between intragastric intubation during late gestation and postpartum stress, induced by pup separation, on maternal behavior and on dams' emotional state and HPA axis function. Rats received intragastric intubation of water on days 12-20 of gestation or remained untreated in their home cage (naïve dams). Pup separation was used as a model of postpartum stress. The procedure consisted of a daily separation of the dam from its litter for 3h from PND 3 until PND 15. Pup separation was carried out in both naïve and intubated dams. The behavioral results indicate that the association of these two stressors significantly decreased arched-back nursing (ABN) and licking and grooming (LG), behaviors considered important parameters to discriminate the high quality of maternal care. Moreover, dams that received both stressors displayed less nest building and blanket nursing behaviors; no effect on the frequency of passive and total nursing was recorded. The analysis of single effects on ABN and LG, revealed that dams that underwent gestational stress induced by intragastric intubation displayed less LG, but ABN was overall unchanged. On the contrary, pup separation stress significantly increased ABN and LG upon reunion of naïve dams with their pups. Treatments per se or the association of both induced modest changes in plasma levels of allopregnanolone and corticosterone that likely did not influence maternal care. These data show that the association of a mild stress during gestation with an unfavorable experience after parturition had a significant impact on maternal care. This effect seems independent from HPA axis activation or from changes in emotional state; further studies would be necessary to ascertain the neural changes that could contribute to altered maternal behavior in stressed mothers. Moreover, these results suggest that the use of intragastric intubation during gestation would interfere with measures of drug-induced changes in maternal behavior and likely their consequences on the offspring.

Juvenile social isolation affects maternal care in rats: involvement of allopregnanolone

RATIONALE

Social isolation of rats immediately after weaning is thought to represent an animal model of anxiety-like disorders. Socially isolated virgin females showed a significant decrease in allopregnanolone levels, associated with increased anxiety-related behavior compared with group-housed rats.

OBJECTIVES

The present study investigates whether post-weaning social isolation affects maternal behavior and assesses neuroactive steroid levels in adult female rats during pregnancy and postpartum.

RESULTS

Socially isolated dams displayed a reduction in the frequency of arched back nursing (ABN) behavior compared to group-housed dams. In addition, both total and active nursing were lower in socially isolated dams compared to group-housed dams. Compared to virgin females, pregnancy increases allopregnanolone levels in group-housed as well as isolated dams and such increase was greater in the latter group. Compared to pregnancy levels, allopregnanolone levels decreased after delivery and this decrease was more pronounced in isolated than group-housed dams. Moreover, the fluctuations in plasma corticosterone levels that occur in late pregnancy and during lactation follow a different pattern in socially isolated vs. group-housed rats.

CONCLUSIONS

The present results show that social isolation in female rats decreases maternal behavior; this effect is associated with lower allopregnanolone concentrations at postpartum, which may account, at least in part, for the poor maternal care observed in socially isolated dams. In support of this conclusion is the finding that finasteride-treated dams, which display a decrease in plasma allopregnanolone levels, also showed a marked reduction in maternal care, suggesting that allopregnanolone may contribute to the quality of maternal care.

The relationship between weight gain during pregnancy and allopregnanolone levels: a longitudinal study

OBJECTIVE

Large weight gain during pregnancy is a risk factor for complications for mother and fetus. Hunger and satiety are regulated in the hypothalamus, where the gamma-amino-butyric acid system (GABA) has an important role. Allopregnanolone, a progesterone metabolite, increases during pregnancy and is a potent GABA-A receptor modulating steroid. Allopregnanolone has been shown to induce overeating in rodents. The aim was to investigate whether there is a relationship between weight gain and allopregnanolone concentrations during pregnancy in humans.

DESIGN

A longitudinal, cohort study.

METHODS

Pregnant women (n = 56) were recruited in primary care in northern Sweden. Allopregnanolone concentrations in plasma were measured using radioimmunoassay and weight was measured in gestational weeks 12 and 35.

RESULTS

Weight increase correlated significantly to allopregnanolone in late pregnancy increase (rs = 0.320; P = 0.016), indicating a positive relationship between weight increase and allopregnanolone increase. A positive relationship was also noted between allopregnanolone in the 35th gestational week and weight increase. Women who gained ≥11 kg during pregnancy showed higher allopregnanolone concentrations in week 35 and higher increase compared to women who increased <11 kg (P = 0.006 and P = 0.009 resp.). There was no difference in weight or allopregnanolone concentrations at the onset of pregnancy.

CONCLUSIONS

The results show a relationship between weight gain during pregnancy and increase in allopregnanolone concentrations.

Increased anxiety-like phenotype in female guinea pigs following reduced neurosteroid exposure in utero

Neurosteroids are essential for aiding proper fetal neurodevelopment. Pregnancy compromises such as preterm birth, prenatal stress and intrauterine growth restriction are associated with an increased risk of developing behavioural and mood disorders, particularly during adolescence. These pathologies involve the premature loss or alteration of trophic steroid hormones reaching the fetus leading to impaired neurodevelopment. While the specific programming mechanisms are yet to be fully elucidated, in adult life, dysfunctions of allopregnanolone action are prevalent in individuals with depression, post-traumatic stress disorder and anxiety disorders. The objective of this study was to assess if changes in concentrations of the neurosteroid, allopregnanolone, may be a fetal programming factor in priming the brain towards a negative behavioural phenotype during the childhood to adolescent period using a guinea pig model. Pregnant guinea pigs received either vehicle (45% (2-hydroxypropyl)-β-cyclodextrin) or the 5α-reductase inhibitor, finasteride (25mg/kg maternal weight) from gestational age 60 until spontaneous delivery (∼71days gestation). Male and female offspring from vehicle and finasteride treated dams were tested at postnatal day 20 (juvenile-equivalence) in an open field arena, and hippocampus and amygdala subsequently assessed for neurological changes in markers of development and GABA production pathways 24h later. Females with reduced allopregnanolone exposure in utero displayed increased neophobic-like responses to a change in their environment compared to female controls. There were no differences in the neurodevelopmental markers assessed; MAP2, NeuN, MBP, GFAP or GAD67 between intrauterine finasteride or vehicle exposure, in either the hippocampus or amygdala whereas GAT1 staining was decreased. This study indicates that an intrauterine reduction in the supply of allopregnanolone programs vulnerability of female offspring to anxiety-like disorders in juvenility without impacting long term allopregnanolone concentrations.

GABAA receptor modulating steroid antagonists (GAMSA) are functional in vivo

GABAA receptor modulating steroid antagonists (GAMSA) selectively inhibit neurosteroid-mediated enhancement of GABA-evoked currents at the GABAA receptor. 3α-hydroxy-neurosteroids, notably allopregnanolone and tetrahydrodeoxycorticosterone (THDOC), potentiate GABAA receptor-mediated currents. On the contrary, various 3β-hydroxy-steroids antagonize this positive neurosteroid-mediated modulation. Importantly, GAMSAs are specific antagonists of the positive neurosteroid-modulation of the receptor and do not inhibit GABA-evoked currents. Allopregnanolone and THDOC have both negative and positive actions. Allopregnanolone can impair encoding/consolidation and retrieval of memories. Chronic administration of a physiological allopregnanolone concentration reduces cognition in mice models of Alzheimer's disease. In humans an allopregnanolone challenge impairs episodic memory and in hepatic encephalopathy cognitive deficits are accompanied by increased brain ammonia and allopregnanolone. Hippocampal slices react in vitro to ammonia by allopregnanolone synthesis in CA1 neurons, which blocks long-term potentiation (LTP). Thus, allopregnanolone may impair learning and memory by interfering with hippocampal LTP. Contrary, pharmacological treatment with allopregnanolone can promote neurogenesis and positively influence learning and memory of trace eye-blink conditioning in mice. In rat the GAMSA UC1011 inhibits an allopregnanolone-induced learning impairment and the GAMSA GR3027 restores learning and motor coordination in rats with hepatic encephalopathy. In addition, the GAMSA isoallopregnanolone antagonizes allopregnanolone-induced anesthesia in rats, and in humans it antagonizes allopregnanolone-induced sedation and reductions in saccadic eye velocity. 17PA is also an effective GAMSA in vivo, as it antagonizes allopregnanolone-induced anesthesia and spinal analgesia in rats. In vitro the allopregnanolone/THDOC-increased GABA-mediated GABAA receptor activity is antagonized by isoallopregnanolone, UC1011, GR3027 and 17PA, while the effect of GABA itself is not affected.

Women with premenstrual dysphoric disorder have altered sensitivity to allopregnanolone over the menstrual cycle compared to controls-a pilot study

RATIONALE

In premenstrual dysphoric disorder (PMDD), a condition that afflicts 3-8 % of women in fertile ages, the cyclic recurrence of debilitating mood symptoms is restricted to the luteal phase of the menstrual cycle. The progesterone metabolite allopregnanolone is produced by the corpus luteum, and circulating levels are reflected in the brain. Allopregnanolone is a modulator of the GABAA receptor, enhancing the effect of γ-aminobutyric acid (GABA). Previous studies have demonstrated different sensitivity to other GABAA receptor agonists, i.e., benzodiazepines, alcohol, and pregnanolone, in PMDD patients compared to controls.

OBJECTIVES

This study aimed to investigate the sensitivity to intravenous allopregnanolone over the menstrual cycle in PMDD patients.

METHODS

Allopregnanolone, 0.05 mg/kg, was administered intravenously once in the mid-follicular and once in the luteal phase of the menstrual cycle to 10 PMDD patients and 10 control subjects. The saccadic eye velocity (SEV) was recorded by electrooculography as a measurement of functional GABAA receptor activity, at baseline and repeatedly after the injection. A mixed model was used to analyze data.

RESULTS

There was a highly significant group × phase interaction in the SEV response to allopregnanolone (F(1,327.489) = 12.747, p < 0.001). In the PMDD group, the SEV response was decreased in the follicular phase compared to the luteal phase (F(1,168) = 7.776, p = 0.006), whereas in the control group, the difference was opposite during the menstrual cycle (F(1,158.45) = 5.70, p = 0.018).

CONCLUSIONS

The effect of exogenous allopregnanolone is associated with menstrual cycle phase in PMDD patients and in controls. The results suggest an altered sensitivity to allopregnanolone in PMDD patients.

Women with PTSD have a changed sensitivity to GABA-A receptor active substances

RATIONALE

The use of benzodiazepines in treating anxiety symptoms in patients with posttraumatic stress disorder (PTSD) has been debated. Studies on other anxiety disorders have indicated changed sensitivity to GABA-A receptor active substances.

OBJECTIVE

In the present study, we investigated the GABA receptor sensitivity in PTSD patients.

METHODS

Injections of allopreganolone, diazepam, and flumazenil were carried out, each on separate occasions, in 10 drug naïve patients with PTSD compared to 10 healthy controls. Effects were measured in saccadic eye velocity (SEV) and in subjective ratings of sedation.

RESULTS

The PTSD patients were less sensitive to allopregnanolone compared with healthy controls. This was seen as a significant difference in SEV between the groups (p = 0.047). Further, the patients were less sensitive to diazepam, with a significant less increase in sedation compared to controls (p = 0.027). After flumazenil injection, both patients and controls had a significant agonistic effect on SEV, leading to decreased SEV after injection. The patients also responded with an increase in sedation after flumazenil injection, while this was not seen in the controls.

CONCLUSIONS

Patients with PTSD have a changed sensitivity to GABA-A receptor active substances. As a consequence of this, benzodiazepines and other GABA-A receptor active compounds such as sleeping pills will be less useful for this group of patients.

Sex differences in the outcome of juvenile social isolation on HPA axis function in rats

Women are more likely than men to suffer from anxiety disorders and major depression. These disorders share hyperresponsiveness to stress as an etiological factor. Thus, sex differences in brain arousal systems and their regulation by chronic stress may account for the increased vulnerability to these disorders in women. Social isolation is a model of early life stress that results in neurobiological alterations leading to increased anxiety-like and depressive-like behaviors. Here we investigated the sex difference in the effects of post-weaning social isolation on acute stress sensitivity and behavior in rats. In both sexes, social isolation at weaning reduced basal levels of the neuroactive steroid allopregnanolone in the brain and of corticosterone in plasma. Moreover, acute stress increased plasma corticosterone levels in both group-housed and socially isolated male and female rats; however this effect was greater in male than female rats subjected to social isolation. Intriguingly, group-housed female rats showed no change in plasma and brain levels of allopregnanolone after acute foot-shock stress. The absence of stress-induced effects on allopregnanolone synthesis might be due to the physiologically higher levels of this hormone in females vs. males. Accordingly, increasing allopregnanolone levels in male rats blunted the response to foot-shock stress in these animals. Socially isolated male, but not female, rats also display depressive-like behavior and increased hippocampal brain-derived neurotrophic factor (BDNF). The ovarian steroids could "buffer" the effect of this adverse experience in females on these parameters. Finally, the dexamethasone (DEX) suppression test indicated that the chronic stress associated with social isolation impairs feedback inhibition in both sexes in which an increase in the abundance of glucocorticoid receptors (GRs) in the hippocampus was found. Altogether, these results demonstrate that social isolation affects neuroendocrine reactivity to stress, plasticity and emotionality in a sexually dimorphic manner.

Roux-en-Y Gastric Bypass Surgery in Patients with Polycystic Ovary Syndrome and Metabolic Syndrome

BACKGROUND

We aimed to evaluate the impact of Roux-en-Y gastric bypass (RYGB) surgery on metabolic syndrome-related variables in obese women with polycystic ovarian syndrome (PCOS).

METHODS

Thirteen obese women with PCOS (Rotterdam criteria) who met the International Diabetes Federation criteria for metabolic syndrome and who qualified for RYGB were enrolled. Clinical examinations included ovarian ultrasonography and measurement of waist, hip, body mass index and blood pressure. Venous blood samples were taken at the visit before surgery to measure triglyceride, high-density lipoprotein, low-density lipoprotein, fasting glucose, glycated haemoglobin (HbA1c), serum progesterone, allopregnanolone, total testosterone and sex hormone-binding globulin (SHBG) levels. Six months after surgery, patients underwent the same examinations and provided blood samples to analyse the same variables.

RESULTS

At 6 months after surgery, the metabolic syndrome-related variables improved in all patients, except in six patients with anovulatory menstrual cycles who still satisfied the criteria for metabolic syndrome. The metabolic variables normalised and serum progesterone and allopregnanolone levels increased in seven patients with ovulatory cycles. Testosterone and SHBG normalised in all patients at 6 months after surgery. Serum HDL and diastolic blood pressure did not change after surgery. Correlations were found among testosterone, progesterone, allopregnanolone, lipoproteins, triglyceride, fasting glucose and HbA1c levels, which was interpreted as progesterone and its metabolite allopregnanolone may contribute to metabolic abnormalities.

CONCLUSIONS

In PCOS patients, normalisation of metabolic dysfunction may be incomplete by 6 months after RYGB surgery, and the start of ovulatory menstrual cycles may indicate normalisation of metabolic dysfunction.

Women with polycystic ovary syndrome have elevated serum concentrations of and altered GABA(A) receptor sensitivity to allopregnanolone

OBJECTIVE

Several studies have reported that γ-aminobutyric acid (GABA) ergic circuits are involved in the pathophysiology of polycystic ovary syndrome (PCOS). The progesterone metabolite allopregnanolone is a potent GABA(A) -receptor-modulating steroid, and patients may have increased concentrations of allopregnanolone or altered GABAA receptor sensitivity. We investigated both of these possibilities in this study.

PATIENTS

We enrolled 9 women with PCOS and 24 age-matched eumenorrhoeic controls, who were divided into two groups by body mass index (BMI) (16 normal weight and 8 overweight).

MEASUREMENTS

We investigated the effects of allopregnanolone injection on GABA(A) receptor sensitivity in both groups of women. All women received a single intravenous dose of allopregnanolone (0·050 mg/kg). GABA(A) receptor sensitivity was assessed with the saccadic eye velocity (SEV) over 30° (SEV30°), the SEV30°/allopregnanolone concentration ([Allo]) ratio, and sedation, which were measured together with serum allopregnanolone at intervals for 180 min after injection. The controls were tested in the follicular phase of the menstrual cycle.

RESULTS

Baseline allopregnanolone concentrations were higher in the PCOS women than in the normal-weight (P = 0·034) and overweight controls (P = 0·004). The allopregnanolone concentrations after injection were higher in the PCOS women (P = 0·006) and overweight controls (P = 0·037) than in the normal-weight controls. All groups showed a decline in the SEV30°/[Allo] ratio after injection. Allopregnanolone had a smaller effect on the SEV30°/[Allo] ratio in the overweight women (PCOS, P = 0·032; controls, P = 0·007) than in the normal-weight controls. The sedation score after allopregnanolone injection was lower in the PCOS patients than in the controls, but was not different between the two control groups.

CONCLUSIONS

PCOS women had elevated baseline allopregnanolone concentrations compared with follicular-phase controls. All overweight women (PCOS and controls) were less sensitive to allopregnanolone than normal-weight controls.

NPY-Y1 coexpressed with NPY-Y5 receptors modulate anxiety but not mild social stress response in mice

The Y1 and Y5 receptors for neuropeptide Y have overlapping functions in regulating anxiety. We previously demonstrated that conditional removal of the Y1 receptor in the Y5 receptor expressing neurons in juvenile Npy1r(Y5R-/-) mice leads to higher anxiety but no changes in hypothalamus-pituitary-adrenocortical axis activity, under basal conditions or after acute restraint stress. In the present study, we used the same conditional system to analyze the specific contribution of limbic neurons coexpressing Y1 and Y5 receptors on the emotional and neuroendocrine responses to social chronic stress, using different housing conditions (isolation vs. group-housing) as a model. We demonstrated that control Npy1r(2lox) male mice housed in groups show increased anxiety and hypothalamus-pituitary-adrenocortical axis activity compared with Npy1r(2lox) mice isolated for six weeks immediately after weaning. Conversely, Npy1r(Y5R-/-) conditional mutants display an anxious-like behavior but no changes in hypothalamus-pituitary-adrenocortical axis activity as compared with their control littermates, independently of housing conditions. These results suggest that group housing constitutes a mild social stress for our B6129S mouse strain and they confirm that the conditional inactivation of Y1 receptors specifically in Y5 receptor containing neurons increases stress-related anxiety without affecting endocrine stress responses.

Allopregnanolone in the bed nucleus of the stria terminalis modulates contextual fear in rats

Trauma- and stress-related disorders are among the most common types of mental illness affecting the U.S. population. For many of these disorders, there is a striking sex difference in lifetime prevalence; for instance, women are twice as likely as men to be affected by posttraumatic stress disorder (PTSD). Gonadal steroids and their metabolites have been implicated in sex differences in fear and anxiety. One example, allopregnanolone (ALLO), is a neuroactive metabolite of progesterone that allosterically enhances GABA_A receptor activity and has anxiolytic effects. Like other ovarian hormones, it not only occurs at different levels in males and females but also fluctuates over the female reproductive cycle. One brain structure that may be involved in neuroactive steroid regulation of fear and anxiety is the bed nucleus of the stria terminalis (BNST). To explore this question, we examined the consequences of augmenting or reducing ALLO activity in the BNST on the expression of Pavlovian fear conditioning in rats. In Experiment 1, intra-BNST infusions of ALLO in male rats suppressed freezing behavior (a fear response) to the conditioned context, but did not influence freezing to a discrete tone conditioned stimulus (CS). In Experiment 2, intra-BNST infusion of either finasteride (FIN), an inhibitor of ALLO synthesis, or 17-phenyl-(3α,5α)-androst-16-en-3-ol, an ALLO antagonist, in female rats enhanced contextual freezing; neither treatment affected freezing to the tone CS. These findings support a role for ALLO in modulating contextual fear via the BNST and suggest that sex differences in fear and anxiety could arise from differential steroid regulation of BNST function. The susceptibility of women to disorders such as PTSD may be linked to cyclic declines in neuroactive steroid activity within fear circuitry.

Effect of postnatal progesterone therapy following preterm birth on neurosteroid concentrations and cerebellar myelination in guinea pigs

Allopregnanolone protects the fetal brain and promotes normal development including myelination. Preterm birth results in the early separation of the infant from the placenta and consequently a decline in blood and brain allopregnanolone concentrations. Progesterone therapy may increase allopregnanolone and lead to improved oligodendrocyte maturation. The objectives of this study were to examine the efficacy of progesterone replacement in augmenting allopregnanolone concentrations during the postnatal period and to assess the effect on cerebellar myelination – a region with significant postnatal development. Preterm guinea pig neonates delivered at 62 days of gestation by caesarean section received daily s.c. injections of vehicle (2-Hydroxypropyl-β-cyclodextrin) or progesterone (16 mg/kg) for 8 days until term-equivalent age (TEA). Term delivered controls (PND1) received vehicle. Neonatal condition/wellbeing was scored, and salivary progesterone was sampled over the postnatal period. Brain and plasma allopregnanolone concentrations were measured by radioimmunoassay; cortisol and progesterone concentrations were determined by enzyme immunoassay; and myelin basic protein (MBP), proteolipid protein (PLP), oligodendroctye transcription factor 2 (OLIG2) and platelet-derived growth factor receptor-α (PDGFRα) were quantified by immunohistochemistry and western blot. Brain allopregnanolone concentrations were increased in progesterone-treated neonates. Plasma progesterone and cortisol concentrations were elevated in progesterone-treated male neonates. Progesterone treatment decreased MBP and PLP in lobule X of the cerebellum and total cerebellar OLIG2 and PDGFRα in males but not females at TEA compared with term animals. We conclude that progesterone treatment increases brain allopregnanolone concentrations, but also increases cortisol levels in males, which may disrupt developmental processes. Consideration should be given to the use of non-metabolizable neurosteroid agonists.

Quantification of neurosteroids during pregnancy using selective ion monitoring mass spectrometry

Analytical techniques used to quantify neurosteroids in biological samples are often compromised by non-specificity and limited dynamic range which can result in erroneous results. A relatively rapid and inexpensive gas chromatography-mass spectrometry (GC-MS) was developed to simultaneously measure nine neurosteroids, including allopregnanolone, estradiol, and progesterone, as well as 25-hydroxy-vitamin D3 in plasma samples collected from adult women subjects during and after pregnancy. Sample preparation involved solid-phase extraction and derivatization, followed by automated injection on a GC equipped with a mass selective detector (MSD) operated in single ion monitoring (SIM) mode to yield a run time of less than 11min. Method detection limits for all neurosteroids ranged from 30 to 200pg/mL (parts per trillion), with coefficients of variation that ranged from 3% to 5% based on intra-assay comparisons run in triplicate. Although concentrations of estradiol measured by chemiluminescent immunoassay (CIA) were consistent with values determined by GC-MS values, CIA yielded considerable higher values of progesterone, suggesting antibody cross reactions resulting from low specificity. Mean neurosteroid levels and representative time-course data demonstrate the ability of the method to quantify changes in multiple neurosteroids during pregnancy, including rapid declines in neurosteroid levels associated with delivery. This simplified GC-MS method holds particular promise for research and clinical laboratories that require simultaneous quantification of multiple neurosteroids, but lack the resources and expertise to support advanced liquid chromatography-tandem mass spectrometry facilities.

Isoallopregnanolone antagonize allopregnanolone-induced effects on saccadic eye velocity and self-reported sedation in humans

Allopregnanolone (AP) is an endogenous neurosteroid. It modulates the effect of γ-amino-butyric acid (GABA) on the GABA type A (GABAA) receptor, which leads to increased receptor activity. Since the GABA-system is mainly inhibitory, increased AP activity leads to modulation of neuronal activity. In vitro studies of GABAA receptor activity and in vivo animal studies of sedation have shown that AP-induced effects can be inhibited by another endogenous steroid, namely isoallopregnanolone (ISO). In this study we investigated if ISO can antagonize AP-induced effects in healthy female volunteers, via measurements of saccadic eye velocity (SEV) and self-rated sedation. With a single-blind cross-over design, 12 women were studied on three separate occasions; given AP alone or AP in combination with one of two ISO doses. Congruent with previous reports, AP administration decreased SEV and induced sedation and these effects were diminished by simultaneous ISO administration. Also, the ISO effect modulation was seemingly stronger for SEV than for sedation. These effects were observed already at an ISO dose exposure that was approximately half of that of AP. In conclusion, ISO antagonized AP-induced decrease in SEV and self-reported sedation, probably in a non-competitive manner.

The impact of sex hormone concentrations on decision-making in females and males

Human decision-making has been frequently studied and sex differences have been reported. Interestingly, previous results of hormone concentration on decision-making are somewhat inconsistent, regarding the impact of menstrual cycle phase in women or the influence of testosterone concentration on decision-making in women and men. However, the influence of the female sex hormone concentration (estradiol, progesterone) and the impact of oral contraceptive intake have rarely been examined and data regarding the effect of daytime variations of male testosterone are lacking. Moreover if personality factors such as sensation seeking, impulsivity, and anxiety influence decision-making, sex-specific effects, act as modulators is unclear. In the present study 71 women and 45 men were enrolled. All participants performed an evaluated decision-making task measuring risk-taking behavior on the basis of contingencies (Haegler et al., 2010), which can be carried out several times without a learning effect. Saliva samples were collected to obtain estradiol, progesterone, and testosterone levels. Additionally, all participants completed questionnaires measuring various personality factors. Data analysis revealed no sex differences in decision-making and no significant impact of testosterone concentration on behavioral performance in women or men. However, a significant negative correlation between progesterone concentration of women in the luteal phase and their performance in the risk-averse condition was obtained. Interestingly, a significant correlation between trait anxiety and decision-making occurred in females and males. Despite similar risky decision-making of women and men and no influence of testosterone concentration, menstrual cycle phase showed an effect on risk taking in women. In contrary to other studies, our findings provide rather subtle evidence for hormonal influences in decision-making, which may be primarily explained by task factors.

Structure-activity relationship studies on neuroactive steroids in memory, alcohol and stress-related functions: a crucial benefit from endogenous level analysis

RATIONALE

New research findings in the field of neuroactive steroids strongly suggest that to understand their role in physiopathology, it is essential to accurately measure their tissue levels. Through his broad chemical expertise and extensive knowledge of steroids, Dr. Robert H. Purdy pioneered structure-activity relationship studies on these compounds and developed innovative detection assays that are essential to assess their function in biological tissues.

OBJECTIVE

The goal of the present paper is to point out the specific contributions of Dr. Purdy and his collaborators to the current knowledge on the role of neuroactive steroids in the modulation of memory and alcohol- and stress-related effects with particular emphasis on the detection assays he developed to assess their endogenous levels. Reviewed here are the major results as well as the original and valuable methodological strategies issued by the long-term collaboration between Dr Purdy and many scientists worldwide on the investigation of the structure-activity relationship of neuroactive steroids.

RESULTS

Altogether, the data presented herein put forward the original notion that knowledge of the chemical structure of steroids is essential for their detection and the understanding of their role in physiological and pathological conditions, including the stress response.

CONCLUSIONS

The current challenge is to identify and quantify using appropriate methods neuroactive steroids in the context of both animal and clinical studies in order to reveal how their levels change under physiological and disease states. Dr. Purdy passed away in September 2012, but scientists all over the world will always be grateful for his pioneering work on steroid chemistry and for his great enthusiasm in research.

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.

Menstrual phase, depressive symptoms, and allopregnanolone during short-term smoking cessation

Preclinical literature indicates that allopregnanolone (ALLO), a neuroactive steroid metabolized from progesterone, may protect against drug abuse behaviors. It is important to understand how ALLO varies during smoking changes in clinical samples with depressive symptoms (DS) given they are at high risk of smoking relapse. The purpose of this article is to characterize changes in ALLO by menstrual phase during short-term smoking cessation among women with and without DS. At screening, study participants (n = 84) were classified as either having past or current DS (n = 48) or not (n = 36). In a controlled crossover trial design, participants completed 2 testing weeks in the follicular (F; low ALLO) and luteal (L; high ALLO) menstrual phases. During each testing week, blood samples were collected during ad libitum smoking and on the fourth day of biochemically verified smoking abstinence. Participants were, on average, 30.1 ± 6.7 years old, smoked 12.6 ± 5.7 cigarettes per day, and most (73%) were White. The change in ALLO during short-term smoking cessation varied significantly by menstrual phase such that it decreased by 10% in the follicular phase and increased by 31% in the luteal phase. There were no significant differences in ALLO levels by DS group. In premenopausal women, ALLO levels varied by menstrual phase and smoking status, but not DS. Given that other research has indicated L phase is associated with improved smoking cessation outcomes, an increase in ALLO during short-term cessation in the L phase may protect against relapse whereas a decrease in ALLO, as observed in the F phase, may increase risk for relapse.

Allopregnanolone induces a diurnally dependent hyperphagic effect and alters feeding latency and duration in male Wistar rats

AIM

Gamma-aminobutyric acid (GABA)-ergic transmission from the hypothalamus is essential for normal feeding regulation, and hyperphagia can be induced by local application of GABAA -receptor agonists to different feeding-associated brain areas. The food intake in rats varies diurnally and that may influence the effect of GABAA -receptor active compounds. The progesterone metabolite allopregnanolone is a highly potent endogenous positive modulator of the GABAA receptor. Therefore, it is easy to envisage that allopregnanolone would have a hyperphagic effect, but earlier reports in rat have given ambiguous results. However, a contributing factor for the discrepancy may be the time point of the diurnal cycle in which the experiments were performed. The aim of this study was to investigate the effect of allopregnanolone on intake of standard chow in male Wistar rats at different time points of the day.

METHODS

Chow intake was measured after acute administration of allopregnanolone, and feeding behaviour was analysed to detect meal patterns.

RESULTS

We found that allopregnanolone increased chow intake by up to four times in the dark part of the 24-h cycle. The rats ate significantly more, and the effect of allopregnanolone was more prominent in the active (dark) compared with the inactive (light) period. Allopregnanolone also reduced feeding latency and prolonged the meal duration compared with vehicle.

CONCLUSION

Allopregnanolone seems to act at several levels of feeding regulation, that is, to initiate feeding and to prolong the duration of a meal, thereby increasing the meal size, especially in the dark period of the 24-h cycle.

Women with acute intermittent porphyria have a defect in 5α-steroid production during the menstrual cycle

OBJECTIVE

To measure serum concentrations of progesterone, estradiol and 5α- and 5β-reduced progesterone metabolites in the follicular and luteal phases of the menstrual cycle in women with latent acute intermittent porphyria and manifest acute intermittent porphyria in comparison with healthy control women.

DESIGN

A descriptive study with repeated measurements during a complete, ovulatory menstrual cycle.

SETTING

University hospital out-patient clinic.

POPULATION

Thirty-two women with DNA-diagnosed acute intermittent porphyria and 20 healthy control women.

METHODS

Blood samples for serum progesterone, estradiol, allopregnanolone and pregnanolone were drawn on predefined menstrual cycle days, twice in the follicular phase and three times in the luteal phase. Serum levels of estradiol and progesterone were analysed with commercial kits. Allopregnanolone and pregnanolone levels were analysed with radioimmunoassay following diethylether extraction and celite column chromatography.

MAIN OUTCOME MEASURES

Changes in serum levels of progesterone, estradiol, allopregnanolone and pregnanolone throughout the menstrual cycle.

RESULTS

Women with acute intermittent porphyria displayed lower serum concentrations of allopregnanolone in comparison with healthy control women, the difference being most prominent in the luteal phase (p < 0.001). Levels of pregnanolone did not differ significantly between groups. No significant difference was found between women with latent acute intermittent porphyria and manifest acute intermittent porphyria.

CONCLUSIONS

Decreased levels of the 5α-reduced progesterone metabolite allopregnanolone were found in the menstrual cycle of women with acute intermittent porphyria. This has not been reported previously and could indicate a reduced 5α-reductase type 1 capacity in the ovary and liver among these women.

Effects and Mechanisms of 3α,5α,-THP on Emotion, Motivation, and Reward Functions Involving Pregnane Xenobiotic Receptor

Progestogens [progesterone (P(4)) and its products] play fundamental roles in the development and/or function of the central nervous system during pregnancy. We, and others, have investigated the role of pregnane neurosteroids for a plethora of functional effects beyond their pro-gestational processes. Emerging findings regarding the effects, mechanisms, and sources of neurosteroids have challenged traditional dogma about steroid action. How the P(4) metabolite and neurosteroid, 3α-hydroxy-5α-pregnan-20-one (3α,5α-THP), influences cellular functions and behavioral processes involved in emotion/affect, motivation, and reward, is the focus of the present review. To further understand these processes, we have utilized an animal model assessing the effects, mechanisms, and sources of 3α,5α-THP. In the ventral tegmental area (VTA), 3α,5α-THP has actions to facilitate affective, and motivated, social behaviors through non-traditional targets, such as GABA, glutamate, and dopamine receptors. 3α,5α-THP levels in the midbrain VTA both facilitate, and/or are enhanced by, affective and social behavior. The pregnane xenobiotic receptor (PXR) mediates the production of, and/or metabolism to, various neurobiological factors. PXR is localized to the midbrain VTA of rats. The role of PXR to influence 3α,5α-THP production from central biosynthesis, and/or metabolism of peripheral P(4), in the VTA, as well as its role to facilitate, or be increased by, affective/social behaviors is under investigation. Investigating novel behavioral functions of 3α,5α-THP extends our knowledge of the neurobiology of progestogens, relevant for affective/social behaviors, and their connections to systems that regulate affect and motivated processes, such as those important for stress regulation and neuropsychiatric disorders (anxiety, depression, schizophrenia, drug dependence). Thus, further understanding of 3α,5α-THP's role and mechanisms to enhance affective and motivated processes is essential.

Allopregnanolone, a GABAA receptor agonist, decreases gonadotropin levels in women. A preliminary study

Animal studies suggest regulatory effects on the hypothalamic-pituitary-gonad axis by allopregnanolone, an endogenous gamma-aminobutyric acid A (GABA(A)) receptor agonist. Elevated levels of allopregnanolone in women with hypothalamic amenorrhea have been seen. Isoallopregnanolone is an isomer to allopregnanolone, but without GABA(A) receptor effects. The purpose of this study was to investigate effects of allopregnanolone and isoallopregnanolone on gonadotropin levels in healthy women of fertile age. Ten women were given allopregnanolone and five women isoallopregnanolone intravenously in follicular phase. Repeated blood samples were drawn during the test day. Main outcomes were changes in serum levels of follicle-stimulating hormone (FSH), luteinising hormone (LH), oestradiol, and progesterone. Serum-FSH decreased between 5 and 105 min after the allopregnanolone injection (F(16,144)=2.18, p=0.008). Serum-LH was reduced between 5 and 35 min following the allopregnanolone injection (F(16,144)=2.63, p=0.001). Serum-oestradiol and -progesterone were not significantly changed after allopregnanolone injections. No effect on gonadotropin levels were seen after administration of isoallopregnanolone. Allopregnanolone reduces FSH and LH levels in women and the effect might be mediated via a specific GABA(A) receptor activation since isoallopregnanolone lacked this effect. Although the number of women was small, the results suggest a regulatory mechanism on the hypothalamic-pituitary-gonadal axis by allopregnanolon.

Inhibition of 5α-reductase activity in late pregnancy decreases gestational length and fecundity and impairs object memory and central progestogen milieu of juvenile rat offspring

Psychological, physical and/or immune stressors during pregnancy are associated with negative birth outcomes, such as preterm birth and developmental abnormalities. In rodents, prenatal stressors can alter the expression of 5α-reductase enzymes in the brain and may influence cognitive function and anxiety-type behaviour in the offspring. Progesterone plays a critical role in maintaining gestation. In the present study, it was hypothesised that 5α-reduced progesterone metabolites influence birth outcomes and/or the cognitive and neuroendocrine function of the offspring. 5α-Reduced steroids were manipulated in pregnant Long-Evans rats via the administration of vehicle, the 5α-reduced, neuroactive metabolite of progesterone, 5α-pregnan-3α-ol-20-one (3α,5α-THP, allopregnanolone; 10 mg/kg/ml, s.c.), or the 5α-reductase inhibitor, finasteride (50 mg/kg/ml, s.c.), daily from gestational days 17-21. Compared to vehicle or 3α,5α-THP treatment, finasteride, significantly reduced the length of gestation and the number of pups per litter found in the dams' nests after parturition. The behaviour of the offspring in hippocampus-dependent tasks (i.e. object recognition, open field) was examined on post-natal days 28-30. Compared to vehicle-exposed controls, prenatal 3α,5α-THP treatment significantly increased motor behaviour in females compared to males, decreased progesterone content in the medial prefrontal cortex (mPFC) and diencephalon, increased 3α,5α-THP and 17β-oestradiol content in the hippocampus, mPFC and diencephalon, and significantly increased serum corticosterone concentrations in males and females. Prenatal finasteride treatment significantly reduced object recognition, decreased hippocampal 3α,5α-THP content, increased progesterone concentration in the mPFC and diencephalon, and increased serum corticosterone concentration in female (but not male) juvenile offspring, compared to vehicle-exposed controls. Thus, inhibiting the formation of 5α-reduced steroids during late gestation in rats reduces gestational length, the number of viable pups per litter, and impairs cognitive and neuroendocrine function in the juvenile offspring.

Changes in functioning of mesolimbic incentive processing circuits during the premenstrual phase

The premenstrual phase of the menstrual cycle is associated with marked changes in normal and abnormal motivated behaviors. Animal studies suggest that such effects may result from actions of gonadal hormones on the mesolimbic dopamine (DA) system. We therefore investigated premenstrual changes in reward-related neural activity in terminal regions of the DA system in humans. Twenty-eight healthy young women underwent functional magnetic resonance imaging on 2 days during the menstrual cycle, once during the late follicular phase and once during the premenstrual phase, in counterbalanced order. Using a modified version of the monetary incentive delay task, we assessed responsiveness of the ventral striatum to reward anticipation. Our results show enhanced ventral striatal responses during the premenstrual as compared to the follicular phase. Moreover, this effect was most pronounced in women reporting more premenstrual symptoms. These findings provide support for the notion that changes in functioning of mesolimbic incentive processing circuits may underlie premenstrual changes in motivated behaviors. Notably, increases in reward-cue responsiveness have previously been associated with DA withdrawal states. Our findings therefore suggest that the sharp decline of gonadal hormone levels in the premenstrual phase may trigger a similar withdrawal-like state.

Effects of voluntary ethanol consumption on emotional state and stress responsiveness in socially isolated rats

Social isolation of rats immediately after weaning is thought to represent an animal model of anxiety-like disorders. This mildly stressful condition reduces the cerebrocortical and plasma concentrations of 3α-hydroxy-5α-pregnan-20-one (3α,5α-TH PROG) as well as increases the sensitivity of rats to the effects of acute ethanol administration on the concentrations of this neuroactive steroid. We further investigated the effects of voluntary consumption of ethanol at concentrations increasing from 2.5 to 10% over 4 weeks of isolation. Isolated rats showed a reduced ethanol preference compared with group-housed animals. Ethanol consumption did not affect the isolation-induced down-regulation of BDNF or Arc, but it attenuated the increase in the cerebrocortical concentration of 3α,5α-TH PROG induced by foot-shock stress in both isolated and group-housed animals as well as increased the percentage of number of entries made by socially isolated rats into the open arms in the elevated plus-maze test. Ethanol consumption did not affect expression of the α₄ subunit of the GABA(A) receptor in the hippocampus of group-housed or isolated rats, whereas it up-regulated the δ subunit throughout the hippocampus under both conditions. The results suggest that low consumption of ethanol may ameliorate some negative effects of social isolation on stress sensitivity and 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.

Voluntary Ethanol Consumption Induced by Social Isolation Reverses the Increase of α(4)/δ GABA(A) Receptor Gene Expression and Function in the Hippocampus of C57BL/6J Mice

Post-weaning social isolation (SI) is a model of prolonged mild stress characterized by behavioral and neurochemical alterations. We used SI in C57BL/6J mice to investigate the effects of ethanol (EtOH) in the free-choice drinking paradigm on gene expression and function of γ-aminobutyric acid type A receptors (GABA_ARs) and the role of neuroactive steroids in the actions of EtOH in the hippocampus. SI stress induced a marked reduction in hippocampal 3α-hydroxy-5α-pregnan-20-one (3α,5α-TH PROG) and was associated with molecular and functional changes of the GABA_AR. The gene expression of the α₄ and δ subunits was increased in the hippocampus of SI C57BL/6J mice; the expression of the γ₂ subunit was decreased whereas that of the α₁ did not change. Patch-clamp recordings in dentate gyrus (DG) granule cells obtained from SI C57BL/6J mice revealed a greater enhancement of tonic currents induced by α-(4,5,6,7-tetrahydroisoxazolo[5,4-c] pyridin-3-ol (THIP) compared to that in control C57BL/6J mice. These neurochemical, molecular and functional changes observed in SI C57BL/6J mice were associated with an increased EtOH intake and EtOH preference. Nevertheless, the increase in EtOH consumption did not restore the reduction in hippocampal 3α,5α-TH PROG induced by SI. EtOH self-administration blocked the changes in gene expression of the α₄ subunit but not those of the δ and γ₂ subunits induced by SI. In addition, EtOH self-administration did not block the SI-induced changes in GABA_AR-mediated tonic inhibition in hippocampal granule cells but increased the frequency of basal GABAergic sIPSCs in DG granule cells. We conclude that self-administration of EtOH selectively abolishes the increase of α₄ subunit but not other neurochemical, molecular, and functional modifications induced by SI prolonged mild stress.

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.

Neurosteroids for a successful pregnancy

Steroid hormones play a critical role in the initiation and maintenance of pregnancy. In particular, the important role that the progesterone metabolite, and neurosteroid, allopregnanolone, may play in fetal and adolescent development is becoming increasingly evident. Unlike steroid hormones, neurosteroids act at nontraditional targets in the central and peripheral nervous systems, including GABA(A) receptor complexes. This commentary discusses the three works in this issue that elucidate the important role of allopregnanolone in the mechanisms that regulate stress hypo-sensitivity of rodents in late pregnancy, neuroprotective effects in fetal sheep exposed to a hypoxic insult, and the continuing role that prefrontal cortex formation of allopregnanolone may play on the cognitive development of gestationally stressed rat offspring, grown to adolescence. The narrative that these works comprise was facilitated by the 5(th) International Meeting on Steroids and the Nervous System (Torino, Italy), which is organized to update our knowledge on the relationships between steroid hormones synthesized in different organs and the nervous system. Topics covered in this most recent meeting included sex differences in, and hormonal influences on, cannabinoid-regulated biology; steroids and pain; the importance of co-regulatory factors for steroid receptor action in the brain; mechanism and role of estrogen-induced nonclassical signaling in the brain; vitamin D as the forgotten neurosteroid; neurosteroids and GABA(A) receptors; and pathogenic mechanisms mediated by glucocorticoid receptors in psychiatric disorders. The 6(th) International Meeting on Steroids and the Nervous System will be held in Torino, Italy in February 2011.

Anti-anxiety, cognitive, and steroid biosynthetic effects of an isoflavone-based dietary supplement are gonad and sex-dependent in rats

Isoflavone-rich diets are associated with reduced menopausal symptoms and lowered risk of cancers of reproductive tissues. Isoflavones may mimic some effects of estrogen by binding to estrogen receptors, and/or altering steroid availability. Despite their potential health benefits, neither the effects, nor mechanisms, of isoflavones are well understood. We hypothesized that isoflavones would alter behavior and physiology of rats in sex and/or gonad-dependent manner. An isoflavone-based, commercially-available, dietary supplement was administered via subcutaneous implantation to female and male, intact and gonadectomized Long-Evans rats. Affective (elevated plus-maze), cognitive (water-maze), and reproductive (sexual) behavior was examined. Weights of reproductive structures were measured, as an index of trophic effects. Steroid levels in circulation and brain regions associated with behavioral measures were evaluated by radioimmunoassay. The supplement increased anti-anxiety behavior of intact, but not gonadectomized, rats. The supplement enhanced visual-spatial performance of all rats, but this effect was most evident among proestrous female rats, which had the poorest spatial performance. There were neither effects of the supplement on sexual behavior, mass of reproductive tissues, nor plasma steroid levels. The supplement increased levels of 5α-androstane,17ß-diol-3α-diol (3α-diol) in the hippocampus (but not other brain regions) of gonadectomized females. Thus, the supplement altered anxiety and cognitive behavior and brain production of steroids; however, the anti-anxiety effects were limited to rats with an intact reproductive axis and effects on cognitive performance and neurosteriodogenesis were most evident among intact and gonadectomized, female rats respectively.

Differential activation of the periaqueductal gray by mild anxiogenic stress at different stages of the estrous cycle in female rats

The effect of acute exposure to mild anxiogenic stress on cutaneous nociceptive threshold was investigated in female Wistar rats at different stages of the estrous cycle. Baseline tail flick latencies did not change significantly during the cycle. However after brief exposure to vibration stress (4 Hz for 5 min), rats in late diestrus, but not at other cycle stages, developed a hyperalgesia (decrease in tail flick latency). Animals in late diestrus revealed a more than fivefold increase in the density of Fos-like immunoreactive nuclei in the dorsolateral, lateral, and ventrolateral columns in the caudal half of the periaqueductal gray matter (PAG). There was no change in the density of Fos-like immunoreactive nuclei in the PAG in rats in estrus and early diestrus, although rats in proestrus showed a smaller (50%) but significant increase. Rats undergoing withdrawal from a progesterone dosing regimen (5 mg/kg i.p. twice daily for 6 days) designed to mimic the fall in progesterone that occurs naturally during late diestrus, exhibited a stress-induced hyperalgesia that was similar to animals in late diestrus and a significant increase in Fos-positive cells in the PAG. We suggest that falling levels of progesterone during late diestrus may be a predisposing factor for the development of stress-induced hyperalgesia, which is linked to differential activation of descending pain control circuits in the PAG. Similar changes in women, when progesterone levels fall during the late luteal phase of the menstrual cycle, may contribute to the development of premenstrual symptoms that include increased anxiety and hyperalgesia.

Cardiovascular, hormonal, and emotional responses to the TSST in relation to sex and menstrual cycle phase

The prevalence of stress disorders differs between men and women. An understanding of how men and women vary in acute stress responses may help to understand these sex differences. We compared responses to the TSST and a control task in healthy men (N=28) and women tested in two phases (Follicular N=29, Luteal N=23) of the menstrual cycle. Men exhibited greater cortisol responses to stress than women in either phase. Luteal women exhibited the greatest subjective and allopregnanolone responses to stress, whereas follicular women exhibited blunted noradrenaline responses. Partial correlations controlling for group differences revealed that individuals who were most sensitive to the subjective effects of stress exhibited the largest salivary cortisol, noradrenaline, and allopregnanolone responses and the smallest progesterone responses to stress. We discuss our findings in the context of sex differences in the prevalence of stress-linked disorders.

Neural mechanisms underlying changes in stress-sensitivity across the menstrual cycle

Hormonal fluctuations across the menstrual cycle are thought to play a central role in premenstrual mood symptoms. In agreement, fluctuations in gonadal hormone levels affect brain processes in regions involved in emotion regulation. Recent findings, however, implicate psychological stress as a potential mediating factor and thus, we investigated whether effects of moderate psychological stress on relevant brain regions interact with menstrual cycle phase. Twenty-eight healthy women were tested in a crossover design with menstrual cycle phase (late luteal versus late follicular) and stress (stress induction versus control) as within-subject factors. After stress induction (or control), we probed neural responses to facial expressions using fMRI. During the late luteal phase, negative affect was highest and the stress-induced increase in heart rate was mildly augmented. fMRI data of the control condition replicate previous findings of elevated amygdala and medial prefrontal cortex responses when comparing the late luteal with the late follicular phase. Importantly, stress induction had opposite effects in the two cycle phases, with unexpected lower response magnitudes in the late luteal phase. Moreover, the larger the increase in allopregnanolone concentration across the menstrual cycle was, the smaller the amygdala and medial prefrontal cortex responses were after stress induction in the late luteal phase. Our findings show that moderate psychological stress influences menstrual cycle effects on activity in the emotion regulation circuitry. These results provide potential insights into how fluctuations in allopregnanolone that naturally occur during the menstrual cycle may change stress vulnerability.

Neurosteroids' effects and mechanisms for social, cognitive, emotional, and physical functions

Hormones are trophic factors that integrate central and peripheral nervous system functions, and can influence social, cognitive, emotional and physical (SCEP) processes. Greater understanding of behavioral and neurobiological underpinnings of mental, cognitive, and/or physical changes with maturation is becoming increasingly important as the world's population ages. There are individual differences in how people age, but the factors that influence these differences are not well understood. Social supports are one factor that may influence the trajectory of age-related processes. The loss of close relationships, especially among older persons, is one of the greatest risk factors for mental and physical decline. Progesterone, secreted by the ovaries, or produced de novo in the brain, is readily converted centrally to 5alpha-pregnan-3alpha-ol-20-one (3alpha,5alpha-THP), and can influence SCEP, through rapid, non-classical steroid-mediated actions. Our hypothesis is that 3alpha,5alpha-THP is a key trophic factor in SCEP and development. Our research has demonstrated that 3alpha,5alpha-THP facilitates social and sexual behavior of rodents, which evokes further increases in 3alpha,5alpha-THP in midbrain and hippocampus, brain areas involved in SCEP. The role of 3alpha,5alpha-THP to influence social and/or sexual experience, and thereby SCEP, is discussed in this review. Further understanding of these neurobiological and/or behavioral factors may lead to findings that ultimately can promote health and prevent disease.

Selected line difference in the effects of ethanol dependence and withdrawal on allopregnanolone levels and 5alpha-reductase enzyme activity and expression

BACKGROUND

Allopregnanolone (ALLO) is a progesterone derivative that rapidly potentiates gamma-aminobutyric acid(A) (GABA(A)) receptor-mediated inhibition and modulates symptoms of ethanol withdrawal. Because clinical and preclinical data indicate that ALLO levels are inversely related to symptoms of withdrawal, the present studies determined whether ethanol dependence and withdrawal differentially altered plasma and cortical ALLO levels in mice selectively bred for differences in ethanol withdrawal severity and determined whether the alterations in ALLO levels corresponded to a concomitant change in activity and expression of the biosynthetic enzyme 5alpha-reductase.

METHODS

Male Withdrawal Seizure-Prone (WSP) and -Resistant (WSR) mice were exposed to 72 hours ethanol vapor or air and euthanized at select times following removal from the inhalation chambers. Blood was collected for analysis of ALLO and corticosterone levels by radioimmunoassay. Dissected amygdala, hippocampus, midbrain, and cortex as well as adrenals were examined for 5alpha-reductase enzyme activity and expression levels.

RESULTS

Plasma ALLO was decreased significantly only in WSP mice, and this corresponded to a decrease in adrenal 5alpha-reductase expression. Cortical ALLO was decreased up to 54% in WSP mice and up to 46% in WSR mice, with a similar decrease in cortical 5alpha-reductase activity during withdrawal in the lines. While cortical gene expression was significantly decreased during withdrawal in WSP mice, there was a 4-fold increase in expression in the WSR line during withdrawal. Hippocampal 5alpha-reductase activity and gene expression was decreased only in dependent WSP mice.

CONCLUSIONS

These results suggest that there are line and brain regional differences in the regulation of the neurosteroid biosynthetic enzyme 5alpha-reductase during ethanol dependence and withdrawal. In conjunction with the finding that WSP mice exhibit reduced sensitivity to ALLO during withdrawal, the present results are consistent with the hypothesis that genetic differences in ethanol withdrawal severity are due, in part, to modulatory effects of GABAergic neurosteroids such as ALLO.

Estrogen action: a historic perspective on the implications of considering alternative approaches

In the 50 years since the initial reports of a cognate estrogen receptor (ER), much has been learned about the diverse effects and mechanisms of estrogens, such as 17beta-estradiol (E(2)). This expert narrative review briefly summarizes perspectives and/or recent work of the authors, who have been addressing different aspects of estrogen action, but take a common approach of using alternative considerations to gain insight into mechanisms with clinical relevance, and inform future studies, regarding estrogen action. Their "Top Ten" favorite alternatives that are discussed herein are as follows. 1 - E(2) has actions by binding to a receptor that do not require its enzymatic conversion. 2 - Using a different strategy for antibody binding could make the estrogen receptor (ER) more discernible. 3 - Blocking ERs, rather than E(2) production, may be a useful strategy for breast cancer therapy. 4 - Secretion of alpha-fetoprotein (AFP), rather than only levels of E(2) and/or progesterone, may influence breast cancer risk. 5 - A peptide derived from the active site of AFP can produce the same benefits of the entire endogenous protein in endocrine cancers. 6 - Differential distribution of ER subtypes in the body and brain may underlie specific effects of estrogens. 7 - ERbeta may be sufficient for the trophic effects of estrogen in the brain, and ERalpha may be the primary target of trophic effects in the body. 8 - ERbeta may play a role in the trophic effects of androgens, and may also be relevant in the periphery. 9 - Downstream of E(2)'s effects at ERbeta, there may be consequences for biosynthesis of progestogens and/or androgens. 10 - Changes in histones and/or other factors, which may be downstream of ERbeta, potentially underlie the divergent effects of E(2) in the brain and peripheral tissues.

Progestogens and estrogen influence impulsive burying and avoidant freezing behavior of naturally cycling and ovariectomized rats

Steroid hormones, progesterone and estradiol, may influence approach and/or anxiety behavior. Female rats in behavioral estrous, have elevated levels of these steroid hormones and demonstrate more approach and less anxiety behavior than do diestrous rats. Ovariectomy obviates these cyclic variations and systemic progesterone and/or estrogen replacement can enhance approach and anti-anxiety behavior. However, the role of progesterone and/or estrogen in mediating impulsive, avoidant and/or fear behaviors requires further investigation. We hypothesized that if progesterone and/or estrogen influences impulsivity and/or fear then rats in behavioral estrous would demonstrate less impulsive behavior in a burying task and freezing behavior in a conditioned fear task than will diestrous rats. Ovariectomized rats administered progesterone and/or estrogen would show less impulsive burying and freezing behaviors than will vehicle-administered rats. Experiment 1: Naturally cycling rats were tested in marble burying or conditioned fear when they were in behavioral estrous or diestrous. Experiment 2: Ovariectomized rats were administered progesterone, estrogen or vehicle, then tested in marble burying or conditioned fear. Results of Experiment 1 show rats in behavioral estrous demonstrate less impulsive burying and less freezing behavior than diestrous rats. Results of Experiment 2 show administration of progesterone or both estrogen and progesterone decreases impulsive burying and each decrease freezing behavior compared to vehicle. Thus, progesterone and/or estrogen may mediate impulsive and/or avoidant behavior.

Hyperalgesia in the setting of anxiety: sex differences and effects of the oestrous cycle in Wistar rats

Sex differences to noxious thermal cutaneous stimulation were compared in Wistar rats. Male and female rats showed similar baseline tail flick latencies. However, sex differences emerged when nociceptive testing was carried out in the setting of mild non-noxious anxiogenic stress (4Hz vibration for 5min). On cessation of vibration stress 16/35 (46%) of male rats showed hyperalgesia (decrease in tail flick latency lasting >20min) whist the reminder showed a brief (<2min) hypoalgesia. In 15 animals re-tested the next day, stress-induced hyperalgesia was reproducible (n=7) but the hypoalgesia initially present in 8 rats was less stable, being reduced (n=2) or replaced by weak hyperalgesia (n=3) in some cases. The response of females was oestrous cycle dependent. On cessation of the vibration stress, females in late dioestrus displayed rapid onset hyperalgesia lasting 10min (n=12) whilst others showed either brief (<2min) hypoalgesia (proestrus, n=13 and early dioestrus, n=9) or brief (<2min) delayed hyperalgesia (oestrus, n=16). On re-testing the next day, when most rats were in a different stage of their cycle, the responsiveness of individual female rats changed according to cycle stage. Thus in females, stage of the oestrous cycle rather than trait differences between individuals appears to be the important determinant of responsiveness to stress. Hyperalgesia in females in late dioestrus correlated with increased anxiety behaviour in a novel environment: rats in late dioestrus showed longer latencies to re-enter the inner zone of an open field compared to rats in other cycle stages. Rats undergoing withdrawal from a progesterone dosing regimen (5mgkg(-1) IP twice daily for 6 days) to mimic the fall in progesterone that occurs naturally during late dioestrus, exhibited a stress-induced hyperalgesia similar to animals in late dioestrus. Falling levels of progesterone during late dioestrus may therefore be a pre-disposing factor for the development of stress-induced hyperalgesia in females.

Hormonal, cardiovascular, and subjective responses to acute stress in smokers

RATIONALE

There are complex relationships between stress and smoking; smoking may reduce the emotional discomfort of stress, yet nicotine activates stress systems and may alter responses to acute stress. It is important to understand how smoking affects physiological and psychological outcomes after stress and how these may interact to motivate smoking.

OBJECTIVES

This study aimed to examine the magnitude and time course of hormonal, cardiovascular, and psychological responses to acute psychosocial stress in smokers and non-smokers to investigate whether responses to acute stress are altered in smokers.

MATERIALS AND METHODS

Healthy male non-smokers (n = 20) and smokers (n = 15) participated in two experimental sessions involving a standardized public speaking stress procedure and a control non-stressful task. The outcome measures included self-reported mood, cardiovascular measures (heart rate and blood pressure), and plasma hormone levels (noradrenaline, cortisol, progesterone, and allopregnanolone).

RESULTS

Smokers exhibited blunted increases in cortisol after the Trier Social Stress Test, and they reported greater and more prolonged subjective agitation than non-smokers. Stress-induced changes in progesterone were similar between smokers and non-smokers, although responses overall were smaller among smokers. Stress did not significantly alter levels of allopregnanolone, but smokers exhibited lower plasma concentrations of this neurosteroid.

CONCLUSIONS

These findings suggest that smoking dampens hormonal responses to stress and prolongs subjective discomfort. Dysregulated stress responses may represent a breakdown in the body's ability to cope efficiently and effectively with stress and may contribute to smokers' susceptibility to acute stress, especially during abstinence.

Studies of pharmacokinetic and pharmacodynamic properties of isoallopregnanolone in healthy women

RATIONALE

The pharmacokinetics and behavioral effects of isoallopregnanolone (3beta-hydoxy-5alpha-pregnan-20-one) in women are not known.

OBJECTIVES

Allopregnanolone (3alpha-hydoxy-5alpha-pregnan-20-one) is a well-known neurosteroid, acting via the GABA(A) receptor in the human brain. The naturally occurring progesterone metabolite isoallopregnanolone is the 3beta-stereoisomer of allopregnanolone. Prior studies have concluded that isoallopregnanolone has no effect on the GABA(A) receptor. However, an antagonistic effect of isoallopregnanolone to allopregnanolone on the GABA(A) receptor has been shown in animal and in vitro studies. The purpose of this study was to evaluate the pharmacokinetics and behavioral effects of isoallopregnanolone in humans.

MATERIALS AND METHODS

Six healthy women were given three increasing doses of isoallopregnanolone intravenously in the follicular phase. Repeated blood samples for analyses of isoallopregnanolone and allopregnanolone concentrations were drawn. Saccadic eye movement variables, self-rated sedation, and mood rating scales were used during the test day. A Likert scale for prospective symptoms was used to measure daily fluctuations during the ongoing menstrual cycle.

RESULTS

Exogenously administered isoallopregnanolone produced a dose-dependent increase in the serum concentration of isoallopregnanolone. In parallel, there was also a rise in the allopregnanolone concentration. There was a decrease in saccadic eye movement variables, but no effect was found on self-rated sedation or mood and no changes were seen in prospective symptoms during the menstrual cycle.

CONCLUSIONS

After administration of isoallopregnanolone at a cumulative dose of 0.20 mg/kg, no adverse effects were observed. There is a metabolism of isoallopregnanolone to allopregnanolone, most likely explaining the effects on the saccadic eye movements.

Hormonal influences on seizures: basic neurobiology

There are sex differences and effects of steroid hormones, such as androgens, estrogens, and progestogens, that influence seizures. Androgens exert early organizational and later activational effects that can amplify sex/gender differences in the expression of some seizure disorders. Female-typical sex steroids, such as estrogen (E2) and progestins, can exert acute activational effects to reduce convulsive seizures and these effects are mediated in part by the actions of steroids in the hippocampus. Some of these anticonvulsive effects of sex steroids are related to their formation of ligands which have agonist-like actions at gamma-aminobutyric acid (GABAA) receptors or antagonist actions at glutamatergic receptors. Differences in stress, developmental phase, reproductive status, endocrine status, and treatments, such as anti-epileptic drugs (AEDs), may alter levels of these ligands and/or the function of target sites, which may mitigate differences in sensitivity to, and/or tolerance of, steroids among some individuals. The evidence implicating sex steroids in differences associated with hormonal, reproductive, developmental, stress, seizure type, and/or therapeutics are discussed.

Alcohols which have been in contact with any plastics may interfere in radioimmunoassays of progesterone

In recent years there has been increasing use of plastic rather than glass containers for many liquids, including wine. However we have found that residue from commercially obtained 'pure' ethanol dispensed in plastic bottles interferes in some biochemical assays. We have observed a volume-dependent decrease in maximally bound ligand in radioimmunoassays of progesterone. The resulting shift in the standard curve leads to an underestimation of the analyte concentrations and to altered estimation of cross reactivity by competing ligands. These effects became apparent in assays with high sensitivity (500 pg or less). All sources of ethanol obtainable in Quebec contained impurities. A similar effect was also produced by 'pure' methanol. The reduction in maximally bound ligand was amplified when the alcohol was aliquoted using plastic pipette tips. We conclude that alcohols which have had any contact with plastics are not safe to use in immunoassays of progesterone (or its metabolites as estimated according to cross-reactivity after HPLC) and may affect other assays. If the use of alcohol and plastic tips cannot be avoided, the amount of alcohol used should be reduced to 1% or less. This can be accomplished by preparing steroid standards in assay buffers containing albumin or gelatin, which enhance the solubility of steroids in aqueous media.

Increasing 3alpha,5alpha-THP following inhibition of neurosteroid biosynthesis in the ventral tegmental area reinstates anti-anxiety, social, and sexual behavior of naturally receptive rats

The progesterone metabolite and neurosteroid, 5alpha-pregnan-3alpha-ol-20-one (3alpha,5alpha-THP), has actions in the midbrain ventral tegmental area (VTA) to modulate lordosis, but its effects on other reproductively relevant behaviors are not well understood. Effects on exploration, anxiety, and social behavior resulting from inhibition of 3alpha,5alpha-THP formation, as well as 3alpha,5alpha-THP enhancement, were investigated in the midbrain VTA. Naturally sexually receptive, female rats (n=8-10/group) received infusions aimed at the midbrain VTA of vehicle, PK11195 (an inhibitor of neurosteroidogenesis), and/or indomethacin (an inhibitor of 3alpha,5alpha-THP formation from prohormones), and were subsequently infused with vehicle or FGIN 1-27 (a neurosteroidogenesis enhancer). The rats were then assessed in a behavioral battery that examined exploration (open field), anxiety (elevated plus maze), social (social interaction), and sexual (paced mating) behavior. Inhibition of 3alpha,5alpha-THP formation decreased exploratory, anti-anxiety, social, and sexual behavior, as well as midbrain 3alpha,5alpha-THP levels. Infusions of FGIN 1-27 following 3alpha,5alpha-THP inhibition restored these behaviors and midbrain 3alpha,5alpha-THP levels to those commensurate with control rats that had not been administered inhibitors. These findings suggest that 3alpha,5alpha-THP formation in the midbrain VTA may influence appetitive, as well as consummatory, aspects of mating behavior.