Inga-Maj Johansson

Allopregnanolone inhibits learning in the Morris water maze

The progesterone metabolite allopregnanolone (3alpha-OH-5alpha-pregnane-20-one) inhibits neural functions, enhancing the GABA induced GABA(A) receptor activation. This effect is benzodiazepine like and benzodiazepines are known to impair memory. Acute effects of allopregnanolone on the hippocampus dependent spatial learning in the Morris water maze have not been studied. Adult male Wistar rats where injected (i.v.) with allopregnanolone (2 mg/kg), or vehicle, daily for 11 days. At 8 or 20 min after each injection, studies of place navigation were performed in the Morris water maze. Allopregnanolone concentrations in plasma and in nine different brain areas where analyzed by radioimmunoassay. The latency to find the platform was increased 8 min after the allopregnanolone injection, while normal learning was seen after 20 min. Swim speed did not differ between groups. A higher number of rats were swimming close to the pool wall (thigmotaxis) in the 8 min allopregnanolone group compared to the other groups. Allopregnanolone concentrations in the brain tissue at 8 min were 1.5 to 2.5 times higher then at 20 min after the allopregnanolone injections. After vehicle injections the brain concentrations of allopregnanolone were at control levels. Plasma concentrations of allopregnanolone followed the same pattern as in the brain, with the exception of an increase 8 min after vehicle injections. The natural progesterone metabolite allopregnanolone can inhibit learning in the Morris water maze, an effect not caused by motor impairment. The learning impairment might be due to a combination of changed swimming behavior and difficulties in navigation.

The Role of Hormones and Hormonal Treatments in Premenstrual Syndrome

Premenstrual syndrome (PMS) is a menstrual cycle-linked condition with both mental and physical symptoms. Most women of fertile age experience cyclical changes but consider them normal and not requiring treatment. Up to 30% of women feel a need for treatment. The aetiology is still unclear, but sex steroids produced by the corpus luteum of the ovary are thought to be symptom provoking, as the cyclicity disappears in anovulatory cycles when a corpus luteum is not formed. Progestogens and progesterone together with estrogen are able to induce similar symptoms as seen in PMS. Symptom severity is sensitive to the dosage of estrogen. The response systems within the brain known to be involved in PMS symptoms are the serotonin and GABA systems. Progesterone metabolites, especially allopregnanolone, are neuroactive, acting via the GABA system in the brain. Allopregnanolone has similar effects as benzodiazepines, barbiturates and alcohol; all these substances are known to induce adverse mood effects at low osages in humans and animals. SSRIs and substances inhibiting ovulation, such as gonadotrophin-releasing hormone (GnRH) agonists, have proven to be effective treatments. To avoid adverse effects when high dosages of GnRH agonists are sed, add-back hormone replacement therapy is recommended. Spironolactone also has a beneficial effect, although not as much as SSRIs and GnRH agonists

Pathogenesis in menstrual cycle-linked CNS disorders.

Abstract: That 3alpha‐hydroxy‐5alpha/beta‐pregnane steroids (GABA steroids) have modulatory effects on the GABA‐A receptor is well known. In behavioral studies in animals high exogenous dosages give concentrations not usually reached in the brain under physiological conditions. Animal and human studies show that GABA‐A receptor‐positive modulators like barbiturates, benzodiazepines, alcohol, and allopregnanolone have a bimodal effect. In pharmacological concentrations they are CNS depressants, anesthetic, antiepileptic, and anxiolytic. In low dosages and concentrations, reached endogenously, they can induce adverse emotional reactions in up to 20% of individuals. GABA steroids can also induce tolerance to themselves and similar substances, and rebound occurs at withdrawal. Menstrual cycle‐linked disorders can be understood by the concept that they are caused by the action of endogenously produced GABA‐steroids through three mechanisms: (a) direct action, (b) tolerance induction, and (c) withdrawal effect. Examples of symptoms and disorders caused by the direct action of GABA steroids are sedation, memory and learning disturbance, clumsiness, increased appetite, worsening of petit mal epilepsy, negative mood as tension, irritability and depression during hormone treatments, and the premenstrual dysphoric disorder (PMDD). A continuous exposure to GABA steroids causes tolerance, and women with PMDD are less sensitive to GABA‐A modulators. A malfunctioning GABA‐A receptor system is related to stress sensitivity, concentration difficulties, loss of impulse control, irritability, anxiety, and depression. An example of withdrawal effect is “catamenial epilepsy,” when seizures increase during menstruation after the withdrawal of GABA steroids. Similar phenomena occur at stress since the adrenals produce GABA steroids during stress.

Neuroactive steroid effects on cognitive functions with a focus on the serotonin and GABA systems.

This article will review neuroactive steroid effects on serotonin and GABA systems, along with the subsequent effects on cognitive functions. Neurosteroids (such as estrogen, progesterone, and allopregnanolone) are synthesized in the central and peripheral nervous system, in addition to other tissues. They are involved in the regulation of mood and memory, in premenstrual syndrome, and mood changes related to hormone replacement therapy, as well as postnatal and major depression, anxiety disorders, and Alzheimers disease. Estrogen and progesterone have their respective hormone receptors, whereas allopregnanolone acts via the GABA(A) receptor. The action of estrogen and progesterone can be direct genomic, indirect genomic, or non-genomic, also influencing several neurotransmitter systems, such as the serotonin and GABA systems. Estrogen alone, or in combination with antidepressant drugs affecting the serotonin system, has been related to improved mood and well being. In contrast, progesterone can have negative effects on mood and memory. Estrogen alone, or in combination with progesterone, affects the brain serotonin system differently in different parts of the brain, which can at least partly explain the opposite effects on mood of those hormones. Many of the progesterone effects in the brain are mediated by its metabolite allopregnanolone. Allopregnanolone, by changing GABA(A) receptor expression or sensitivity, is involved in premenstrual mood changes; and it also induces cognitive deficits, such as spatial-learning impairment. We have shown that the 3beta-hydroxypregnane steroid UC1011 can inhibit allopregnanolone-induced learning impairment and chloride uptake potentiation in vitro and in vivo. It would be important to find a substance that antagonizes allopregnanolone-induced adverse effects.

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.

Environmental enrichment alters nerve growth factor-induced gene A and glucocorticoid receptor messenger RNA expression after middle cerebral artery occlusion in rats.

Housing rats in an enriched environment after focal brain ischemia improves functional outcome without changes in infarct volume, suggesting neuroplastic changes outside the lesion. In this study, permanent occlusion of the middle cerebral artery was followed by housing in an enriched or a standard environment. Nerve growth factor-induced gene A and glucocorticoid receptor messenger RNA expression were determined by in situ hybridization two to 30 days after middle cerebral artery occlusion. Stroke induced a decrease in nerve growth factor-induced gene A messenger RNA expression in cortical areas outside the ischemic lesion and in the CA1 subregion of the hippocampus two to three days after ischemia. This decrease was more prolonged with environmental enrichment, lasting until 20 days. However, 30 days after focal cerebral ischemia, environmental enrichment increased nerve growth factor-induced gene A expression compared to standard housing. A reduction of hippocampal glucocorticoid receptor (type II) messenger RNA two to 12 days after stroke in standard housed rats was restored by environmental enrichment. These data suggest that improved functional outcome induced by environmental enrichment after middle cerebral artery occlusion is associated with dynamically altered expression of nerve growth factor-induced gene A messenger RNA in brain regions outside the ischemic lesion, and sustained levels of hippocampal glucocorticoid receptor messenger RNA expression.

Paradoxical effects of GABA-A modulators may explain sex steroid induced negative mood symptoms in some persons

Some women have negative mood symptoms, caused by progestagens in hormonal contraceptives or sequential hormone therapy or by progesterone in the luteal phase of the menstrual cycle, which may be attributed to metabolites acting on the GABA-A receptor. The GABA system is the major inhibitory system in the adult CNS and most positive modulators of the GABA-A receptor (benzodiazepines, barbiturates, alcohol, GABA steroids), induce inhibitory (e.g. anesthetic, sedative, anticonvulsant, anxiolytic) effects. However, some individuals have adverse effects (seizures, increased pain, anxiety, irritability, aggression) upon exposure. Positive GABA-A receptor modulators induce strong paradoxical effects including negative mood in 3%-8% of those exposed, while up to 25% have moderate symptoms. The effect is biphasic: low concentrations induce an adverse anxiogenic effect while higher concentrations decrease this effect and show inhibitory, calming properties. The prevalence of premenstrual dysphoric disorder (PMDD) is also 3%-8% among women in fertile ages, and up to 25% have more moderate symptoms of premenstrual syndrome (PMS). Patients with PMDD have severe luteal phase-related symptoms and show changes in GABA-A receptor sensitivity and GABA concentrations. Findings suggest that negative mood symptoms in women with PMDD are caused by the paradoxical effect of allopregnanolone mediated via the GABA-A receptor, which may be explained by one or more of three hypotheses regarding the paradoxical effect of GABA steroids on behavior: (1) under certain conditions, such as puberty, the relative fraction of certain GABA-A receptor subtypes may be altered, and at those subtypes the GABA steroids may act as negative modulators in contrast to their usual role as positive modulators; (2) in certain brain areas of vulnerable women the transmembrane Cl(-) gradient may be altered by factors such as estrogens that favor excitability; (3) inhibition of inhibitory neurons may promote disinhibition, and hence excitability. This article is part of a Special Issue entitled: Neuroactive Steroids: Focus on Human Brain.

Selective effects on NGFI-A, MR, GR and NGFI-B hippocampal mRNA expression after chronic treatment with different subclasses of antidepressants in the rat

Abstract. There is a latency period of several weeks before the onset of clinical effect of antidepressant drugs. The detailed mechanisms underlying drug-induced adaptive neuronal changes are not known. To elucidate the involvement of changes in gene expression of candidate transcription factors, we treated rats for 21 days with buspirone, fluoxetine, 8-OH-DPAT and moclobemide. In situ hybridization was used to study mRNAs encoding NGFI-A, NGFI-B and the glucocorticoid receptors, MR and GR. NGFI-A mRNA expression increased profoundly in the hippocampal formation and the cerebral cortex after all drug treatments, especially after moclobemide treatment (77–122% increase); with the exception of buspirone. MR mRNA expression was induced in hippocampal CA1/CA2 subregions (27–37%) by all antidepressants, while moclobemide and 8-OH-DPAT significantly increased GR gene expression mainly in the CA1 region (31–44%). NGFI-B mRNA was significantly decreased in the hippocampal CA3 subfield (23%) and restrosplenial granular cortex (38%) by moclobemide treatment. There are selective effects of antidepressant drugs on specific transcription factors. These may be important for adaptive neuronal and neuroendocrine changes after antidepressant treatment including HPA axis negative feedback regulation.

Effects of postischemic environment on transcription factor and serotonin receptor expression after permanent focal cortical ischemia in rats

Housing rats in an enriched environment improves functional outcome after ischemic stroke, this may reflect neuronal plasticity in brain regions outside the lesion. Which components of the enriched environment that are of greatest importance for recovery after brain ischemia is uncertain. We have previously found that enriched environment and social interaction alone both improve functional recovery after focal cerebral ischemia, compared with isolated housing with voluntary wheel-running. In this study, the aim was to separate components of the enriched environment and investigate the effects on some potential mediators of improved functional recovery; such as the inducible transcription factors nerve growth factor-induced gene A (NGFI-A) and NGFI-B, and the glucocorticoid and serotonin systems. After permanent middle cerebral artery occlusion, rats were divided into four groups: individually housed with no equipment (deprived group), individually housed with free access to a running wheel (running group), housed together in a large cage with no equipment (social group) or in a large cage furnished with exchangeable bars, chains and other objects (enriched group). mRNA expression of inducible transcription factors, serotonin and glucocorticoid receptors was determined with in situ hybridisation 1 month after cerebral ischemia. Rats housed in enriched or social environments showed significantly higher mRNA expression of NGFI-A and NGFI-B in cortical regions outside the lesion and in the CA1 (cornu ammonis region of the hippocampus), compared with isolated rats with or without a running wheel. NGFI-A and NGFI-B mRNA expression in cortex and in CA1 was significantly correlated to functional outcome. 5-Hydroxytryptamine receptor 1A (5-HT(1A)) mRNA expression and binding, as well as 5-HT(2A) receptor mRNA expression were decreased in the hippocampus (CA4 region) of the running wheel rats. Mineralocorticoid receptor gene expression was increased in the dentate gyrus amongst wheel-running rats. No group differences were found in plasma corticosterone levels or mRNA levels of glucocorticoid receptor, corticotropin-releasing hormone, 5-HT(2C) or c-fos. In conclusion, we have found that social interaction is a major component of the enriched environment regarding the effects on NGFI-A and NGFI-B expression. These transcription factors may be important mediators of improved functional recovery after brain infarctions, induced by environmental enrichment.

3beta-20beta-dihydroxy-5alpha-pregnane (UC1011) antagonism of the GABA potentiation and the learning impairment induced in rats by allopregnanolone.

Allopregnanolone is a progesterone metabolite and GABA‐A receptor modulator with benzodiazepine like effects, including decreased learning and memory. In vitro 3β‐hydroxypregnane steroids antagonize allopregnanolone‐induced effects, but no antagonism has been shown in vivo. Our purpose was to evaluate 3β‐20β‐dihydroxy‐5α‐pregnane (UC1011) as a blocker of allopregnanolone‐induced effects in vivo and in vitro in rats. We tested adult male Wistar rats in the Morris water maze 8 min after daily injections (i.v.) of allopregnanolone 2 mg/kg (n = 21); allopregnanolone : UC1011 2 : 6 (n = 7), 2 : 8 (n = 7), 2 : 20 (n = 14) mg/kg; UC1011 20 mg/kg (n = 14); or vehicle (10% 2‐hydroxypropyl‐β‐cyclodextrin, n = 4). Studies of chloride ion uptake into cortical and hippocampal membrane preparations were performed. The latency to find the hidden platform was still high in the allopregnanolone‐injected group on day 6. Day 3–6 rats injected with allopregnanolone and UC1011 (2 : 20 mg/kg) had lower latency (P < 0.05), compared to the allopregnanolone‐injected group. The group that only received UC1011 learned the location of the platform as fast as the controls. There was no significant difference in swim speed between groups. The time spent swimming close to the pool wall was in the allopregnanolone : UC1011 group (2 : 20 mg/kg) significantly decreased (P < 0.05, day 3–6), compared to the allopregnanolone‐injected group. The increased chloride ion uptake induced by increasing dosage of allopregnanolone in the presence of 10 µm GABA was significantly decreased with UC1011 (P < 0.01), in both cortical and hippocampal homogenates. In conclusion, UC1011 can via antagonism at the GABA‐A receptor reduce the negative allopregnanolone effect on learning in the water maze.