Influence of 17beta-estradiol on the synthesis of reduced neurosteroids in the brain (in vivo) and in glioma cells (in vitro): possible relevance to mental disorders in women

GABA Receptors in the Medial Preoptic Area Modulate the Onset of Oestradiol-Induced Maternal Behaviour in Hysterectomised-Ovariectomised, Pregnant Rats

We studied the participation of GABA neurotransmission in the medial preoptic area (mPOA) with respect to the onset of the pup retrieval response and nest building. Pregnant female rats were implanted with bilateral cannulae in the mPOA on day 12 of pregnancy and, on day 16, the females were hysterectomised and ovariectomised and given 200 μg/kg of oestradiol benzoate. Two days later, the females received one of the following intracerebral drug treatments: GABA_B agonist baclofen (200 ng); GABA_B antagonist phaclofen (1 μg); GABA_A antagonist bicuculline (60 ng); or physiological saline. Five minutes after intracerebral infusion, three foster pups were introduced into the females' home cage. The subjects were observed for pup grouping (retrieval) during 15 min, after which the pups were left with the female. During the next 12 h, an observation was made every 1 h to determine whether the pups had been grouped (retrieved) or not. The GABA_B agonist baclofen reduced the proportion of females retrieving pups from 4 to 8 h following pup introduction. By contrast, both the GABA_A antagonist bicuculline and the GABA_B antagonist phaclofen enhanced the proportion of females retrieving pups during the first 3 h of observation. The latency to pup retrieval in subjects treated with the GABA_B agonist baclofen was significantly longer than that in subjects given any of the antagonists. All females built a nest but baclofen reduced nest quality. These data show that activation of GABA_B receptors in the mPOA has an inhibitory effect on basic maternal behaviours, whereas blockade of either the GABA_A or GABA_B receptor facilitates pup retrieval. It is possible that reduced GABAergic tone in the mPOA is a key element in the initiation of maternal behaviours in postparturient rats.

Plasticity of GABAA Receptors during Pregnancy and Postpartum Period: From Gene to Function

Pregnancy needs complex pathways that together play a role in proper growth and protection of the fetus preventing its premature loss. Changes during pregnancy and postpartum period include the manifold machinery of neuroactive steroids that plays a crucial role in neuronal excitability by local modulation of specific inhibitory receptors: the GABAA receptors. Marked fluctuations in both blood and brain concentration of neuroactive steroids strongly contribute to GABAA receptor function and plasticity. In this review, we listed several interesting results regarding the regulation and plasticity of GABAA receptor function during pregnancy and postpartum period in rats. The increase in brain levels of neuroactive steroids during pregnancy and their sudden decrease immediately before delivery are causally related to changes in the expression/function of specific GABAA receptor subunits in the hippocampus. These data suggest that alterations in GABAA receptor expression and function may be related to neurological and psychiatric disorders associated with crucial periods in women. These findings could help to provide potential new treatments for these women's disabling syndromes.

Advances in neurosteroids: role in clinical practice

The steroidogenic endocrine glands and local synthesis both contribute to the pool of steroids present in the central nervous system and peripheral nervous system. Although the synthesis of neurosteroids in the nervous system is now well established, the spectrum of respective functions in regulating neuronal and glial functions remains to be fully elucidated. From the concept of neurosteroids derives another treatment strategy: the use of pharmaceutical agents that increase the synthesis of endogenous neurosteroids within the nervous system. This approach has so far been hampered by lack of knowledge concerning the regulation of the biosynthetic pathways of neurosteroids and their relationship with sex steroids produced by the peripheral gland or with exogenous steroids. The present review summarizes some of the available clinical and experimental findings supporting the critical role of neurosteroids during fertile life and reproductive aging and their relationship with endogenous and exogenous sex steroids. The brain metabolism of synthetic progestins and the implications of DHEA treatment in postmenopausal women will also be discussed.

Neurosteroids in clinical practice: implications for women’s health

The steroidogenic endocrine glands and local synthesis both contribute to the pool of steroids present in the central nervous system (CNS) and peripheral nervous system (PNS). Although the synthesis of neurosteroids in the nervous system is now well established, the spectrum of respective functions in regulating neuronal and glial functions remains to be fully elucidated. From the concept of neurosteroids derives another therapeutical strategy: the use of pharmaceutical agents that increase the synthesis of endogenous neurosteroids within the nervous system. This approach is so far hampered by the lack of knowledge concerning the regulation of the biosynthetic pathways of neurosteroids and their relationship with sex steroids produced by peripheral glands. The present review summarizes some of the available clinical and experimental findings supporting the critical role of neuro-steroids during the fertile life and reproductive aging and their relationship with endogenous and exogenous sex steroids. Brain metabolism of synthethic progestins and the implication of dehydroepiandrosterone (DHEA) treatment in post-menopausal women will be also discussed.

Plasticity and function of extrasynaptic GABA(A) receptors during pregnancy and after delivery

Neuroactive steroids such as 3alpha-hydroxy-5alpha-pregnan-20-one (3alpha,5alpha-THP) are reduced metabolites of progesterone and are thought to play an important physiological role in local modulation of neuronal excitability by "fine-tuning" the action of gamma-aminobutyric acid (GABA) at GABA(A) receptors. Fluctuations in the concentrations of neuroactive steroids in the brain are also thought to contribute to GABA(A) receptor plasticity. We here review results from our laboratory related to the regulation of GABA(A) receptor function and plasticity by changes in the levels of neuroactive steroids during pregnancy and after delivery in rats. Pregnancy is characterized by marked and progressive increases in the plasma and brain concentrations of neuroactive steroids, which are implicated in the changes in mood, anxiety, and other psychiatric states associated with this condition. We have shown that the increases in the brain levels of neuroactive steroids during pregnancy are causally related to changes in the expression of specific GABA(A) receptor subunits and the function of extrasynaptic GABA(A) receptors in the hippocampus.

Estrogen increases latencies to seizures and levels of 5alpha-pregnan-3alpha-ol-20-one in hippocampus of wild-type, but not 5alpha-reductase knockout, mice

Sex steroids can influence seizures. Estrogen (E(2)), progesterone (P(4)), and its metabolite, 5alpha-pregnan-3alpha-ol-20-one (3alpha,5alpha-THP), in particular, have received much attention for exerting these effects. Typically, it is thought that E(2) precipitates seizures, and progestogens, such as P(4) and 3alpha,5alpha-THP, attenuate seizures. However, E(2) may also have antiseizure effects, perhaps in part through its enhancement of the formation of 3alpha,5alpha-THP, which has GABA(A)/benzodiazepine receptor agonist-like actions. To test this hypothesis, male and female, castrated or ovariectomized, wild-type and 5alpha-reductase knockout mice were implanted with Silastic capsules of E(2) or vehicle and then administered pentylenetetrazol (85 mg/kg, ip). Wild-type, but not 5alpha-reductase knockout, mice administered E(2) had significantly longer latencies to myoclonus and increased levels of 3alpha,5alpha-THP in the hippocampus. Thus, some of the anticonvulsive effects of E(2) may involve formation of 3alpha,5alpha-THP in the hippocampus.

Progestin and breast cancer. The missing pieces of a puzzle

The previous assumption that progestin does not promote breast cancer development needs to be re-examined since a growing body of evidence indicates the opposite. Data from recent experimental trials and results from clinical and epidemiological studies on hormonal contraceptives and hormone replacement therapy (HRT) have been confronted with breast cancer cases known from the German database of adverse drug reactions (ADR), reported in association with the use of progestin only contraceptives (POC) and combined oral contraceptives (COC). Also cases reported in association with HRT have been analysed. The available data complement one another showing a tumour promoting potential of progestin, possibly higher than that of a combination of estrogen and progestin. These assumptions are based on the following facts: 1) in estrogen-supplemented animals, progesterone has been shown to reactivate the growth of regressed tumour xenograft obtained from breast cancer cell lines, expressing both estrogen and progesterone receptor; 2) antiprogestin has been revealed to suppress the reactivation of the growth of tumour xenograft and to fully suppress the development of breast cancer in an animal model for BRCA1 gene mutation; 3) metabolites of progesterone have been recognised as potent regulators of cell proliferation, cell detachment and apoptosis; 4) progesterone has been shown to inhibit, in a dose-dependent manner, apoptosis in breast cancer cell lines and apoptosis induced by doxorubicin and 5-fluorouracyl (drugs used in breast cancer treatment); 5) an association between breast cancer and HRT was suspected upon the addition of progestin on a regular basis for the prevention of endometrial cancer; 6) in a randomised placebo-controlled trial on HRT an increased risk of breast cancer was shown for the combination of estrogen and progestin, but not for estrogen alone; 7) in epidemiological studies on POC the recognition of an increased breast cancer risk was most probably impeded due to previously unrecognised systematic selection bias; 8) in a large epidemiological study on the risk of early-onset breast cancer in association with COC an increased risk was detected for COC use up to 1975, but no increased, even a slightly decreased, risk was shown for users of low-dose COC, applied since 1976; 9) a considerably higher number of breast cancer cases have been reported from Germany on POC than on the widespread used COC [corrected] (111 versus 12); 10) the big resemblance among the breast cancers reported for POC and their similarity with breast malignancies diagnosed in pregnancy suggest the existence of a pattern rather than pure coincidence [corrected]

Neurosteroids, neuroactive steroids, and symptoms of affective disorders

Neurosteroids (NS) are steroids synthesized by the brain. Neuroactive steroids (NAS) refers to steroids that, independent of their origin, are capable of modifying neural activities. NAS bind and modulate different types of membrane receptors. The gamma amino butyric acid (GABA) and sigma receptor complexes have been the most extensively studied. Oxidized ring A reduced pregnanes, tetrahydroprogesterone (THP), and tetrahydrodeoxycorticosterone (THDOC) bind to the progesterone intracellular receptor (PR), and in this way can also regulate gene expression. Animal experimentation showed that salient symptoms of depression, viz., anxiety, sleep disturbances, and memory and sexual dysfunctions, are modulated by NAS. In turn, psychotropic drugs modulate NS and NAS levels. NS levels as well as NAS plasma concentrations change in patients with depression syndromes, the levels return to normal baseline with recovery, but normalization is not necessary for successful therapy. Results from current studies on the evolution of nervous systems, including evolutionary developmental biology as well as anatomical and physiological findings, almost preclude a categorical classification of the psychiatric ailments the human brain succumbs to. The persistence in maintaining such essentialist classifications may help to explain why up to now the search for biological markers in psychiatry has been an unrewarding effort. It is proposed that it would be more fruitful to focus on relationships between NAS and symptoms of psychiatric disorders, rather than with typologically defined disorders.

A paracrine component of salient symptoms of depression in Cushing’s of diencephalic origin, and in perimenstrual syndromes: A hypothesis

Interrelationships between adrenocortical secretions and depression syndromes have been known since early in the 20th century. Now, the fact that pregnane and pregnene steroids are also known to be synthesized in the brain (they are termed neurosteroids (NS)), raises the possibility that these natural compounds could have paracrine effects. Adrenocorticotropic hormone (ACTH) can modulate biosynthesis of NSs. 17beta estradiol has been shown to decrease THP concentration in the brain. It is hypothesized that imbalance between stimulatory and depressant NSs induced by ACTH elevation in hypothalamo pituitary dependent Cushing's, and by estrogen concentration changes during the menstrual cycle, may be associated with the pathophysiology of salient symptoms of depression in Cushing's and in perimenstrual syndromes.