Giving a good start to a new life via maternal brain allostatic adaptations in pregnancy

Successful pregnancy requires adjustments to multiple maternal homeostatic mechanisms, governed by the maternal brain to support and enable survival of the growing fetus and placenta. Such adjustments fit the concept of allostasis (stability through change) and have a cost: allostatic load. Allostasis is driven by ovarian, anterior pituitary, placental and feto-placental hormones acting on the maternal brain to promote adaptations that support the pregnancy and protect the fetus. Many women carry an existing allostatic load into pregnancy, from socio-economic circumstances, poor mental health and in ‘developed’ countries, also from obesity. These pregnancies have poorer outcomes indicating negative interactions (failing allostasis) between pre-pregnancy and pregnancy allostatic loads. Use of animal models, such as adult prenatally stressed female offspring with abnormal neuroendocrine, metabolic and behavioural phenotypes, to probe gene expression changes, and epigenetic mechanisms in the maternal brain in adverse pregnancies are discussed, with the prospect of ameliorating poor pregnancy outcomes.     

别孕烯醇酮对6-羟基多巴胺损伤的细胞系SH-SY5Y的保护作用

目的 明确别孕烯醇酮（APα）对6-羟多巴胺（6-OHDA）损伤的SH-SY5Y细胞系的保护作用，并阐明可能的分子机制。方法 向体外培养的SH-SY5Y细胞系中分别加入6-OHDA、APα、γ-氨基丁酸A受体（GABAAR）拮抗剂荷包牡丹碱（Bic）和电压门控L型Ca²⁺通道拮抗剂硝苯地平（nifedipine），采用免疫荧光细胞化学染色方法观察不同组别酪氨酸羟化酶（TH）阳性细胞的变化，Western blotting检测胞质钙调蛋白（CaM）、钙离子 钙调蛋白依赖性蛋白激酶Ⅱ δ3（CaMKⅡδ3），胞核CaMKⅡδ3、脑源性神经营养因子（BDNF）和细胞周期蛋白依赖性激酶（CDK1）表达的变化，采用蛋白质免疫共沉淀验证CaMKⅡδ3与CDK1/BDNF的相互作用。 结果 APα作用后，6-OHDA损伤的SH-SY5Y细胞TH和5-溴脱氧尿嘧啶核苷（BrdU）阳性细胞数目均明显增加，而TH/BrdU双阳性细胞数目无显著变化；同时Western blotting结果表明，SH-SY5Y细胞胞质和胞核上述蛋白的表达与单纯 6-OHDA 组相比也明显上升，经Bic处理后各蛋白增加更为明显。免疫共沉淀结果表明，CaMKⅡδ3与CDK1/BDNF存在相互作用。 结论 APα对6-OHDA损伤的SH-SY5Y细胞的保护中，GABAAR发挥负性调控作用，通过稳定细胞的内环境达到增加TH阳性神经元数量的目的，其中Ca²⁺ -CaM-CaMKⅡδ3信号通路和BDNF与CDK1发挥了关键作用。     

GABAA receptor-acting neurosteroids: A role in the development and regulation of the stress response

Regulation of hypothalamic–pituitary–adrenocortical (HPA) axis activity by stress is a fundamental survival mechanism and HPA-dysfunction is implicated in psychiatric disorders. Adverse early life experiences, e.g. poor maternal care, negatively influence brain development and programs an abnormal stress response by encoding long-lasting molecular changes, which may extend to the next generation. How HPA-dysfunction leads to the development of affective disorders is complex, but may involve GABA_A receptors (GABA_ARs), as they curtail stress-induced HPA axis activation. Of particular interest are endogenous neurosteroids that potently modulate the function of GABA_ARs and exhibit stress-protective properties. Importantly, neurosteroid levels rise rapidly during acute stress, are perturbed in chronic stress and are implicated in the behavioural changes associated with early-life adversity. We will appraise how GABA_AR-active neurosteroids may impact on HPA axis development and the orchestration of the stress-evoked response. The significance of these actions will be discussed in the context of stress-associated mood disorders.     

Effects of Chronic Ethanol Consumption and Withdrawal on the Neuroactive Steroid 3α-Hydroxy-5α-pregnan-20-one in Male and Female Rats

Prolonged alcohol (ethanol) consumption leads to the development of alcohol tolerance and cross-tolerance to some benzodiazepines and barbiturates. In contrast, rats undergoing alcohol withdrawal are sensitized to the anticonvulsant effects of the endogenous GABAA receptor modulator, 3α-hydroxy-5α-pregnan-20-one (3α, 5α-THP). Alterations in endogenous, cerebral cortical levels of 3α, 5α-THP during alcohol withdrawal could contribute to the observed sensitization to 3α, 5α-THP. Therefore, this study investigated plasma and brain levels of 3α,5α-THP, progesterone, and corticosterone during alcohol dependence and withdrawal in the rat. Plasma corticosterone, progesterone (a precursor of 3α,5α-THP) and 3α,5α-THP levels were unchanged in alcohol-dependent animals. Cerebral cortical levels of 3α,5α-THP decreased in dependent male animals, but not in dependent female rats. During alcohol withdrawal, plasma corticosterone and progesterone levels increased in male, but not female rats. However, neither plasma nor cerebral cortical 3α,5α-THP levels were altered from control levels in male or female rats during alcohol withdrawal. Plasma and brain levels of 3α,5α-THP were markedly higher in female compared with male rats. Cerebral cortical levels of 3α,5α-THP during the diestrus phase of the estrus cycle were ˜4 to 6 ng/g, a concentration that may approach physiological relevance. These findings suggest that sensitization to 3α,5α-THP during alcohol withdrawal is not mediated by elevations in brain levels of endogenous 3α,5α-THP in male or female rats. However, elevations in circulating corticosterone and progesterone levels during ethanol withdrawal in male rats may underlie gender differences in allopreg-nanolone sensitivity during ethanol withdrawal.     

别孕烯醇酮对APPswe/PSEN1小鼠黑质多巴胺能神经元的影响

目的 评估别孕烯醇酮（APα）对阿尔茨海默病（AD）小鼠黑质（SN）酪氨酸羟化酶（TH）神经元数目的影响。方法 31只4月龄雄性小鼠采用免疫荧光染色观察和计算各种免疫阳性细胞的数目。结果 双转基因AD小鼠（2×TgAD）APα水平和TH神经元数目均明显减少,且出现在β 淀粉样斑块形成之前。给予APα处理可预防2×TgAD小鼠SN总神经元、TH神经元和TH/5 溴脱氧尿嘧啶核苷（BrdU）神经元数目的下降,但对纹状体TH神经纤维吸光度下降无影响。此外,APα能增加2×TgAD小鼠新生成熟神经元的数目,但对新生胶质细胞数目无影响。结论 2×TgAD小鼠体内低水平APα与多巴胺能神经元下降相关,外源性APα能够通过增加新生TH神经元的形成来恢复2×TgAD小鼠TH神经元的下降。     

Olanzapine plus 17-β estradiol produce antidepressant-like actions in rats forced to swim

Several combinations of effective treatments have been used in the search for higher response rates or more rapid responses than monotherapy to diminish treatment-resistant depression. One strategy is to combine olanzapine plus antidepressant drugs. In preclinical studies in male rats, olanzapine combined with fluoxetine produce antidepressant-like actions and increase the allopregnanolone levels in the brain. 17-β estradiol also produces antidepressant-like actions by increasing allopregnanolone levels. However, the effects of combining olanzapine with 17-β estradiol in the forced swimming test have not been tested before. Thus, systemic injections of vehicle plus olanzapine, or fluoxetine (20.0 mg/kg; 25.0 mg/kg) or 17-β estradiol (10.0 μg/rat; 20.0 μg/rat) reduced immobility by increasing active behaviors, which were cancelled by finasteride (finasteride was used to block the endogenous production of allopregnanolone by the brain) in ovariectomized rats forced to swim. Subthreshold doses of olanzapine (2.5 mg/kg) combined with subthreshold doses of 17-β estradiol (5.0 μg/rat) produced antidepressant-like actions, as did the combination subthreshold dose of olanzapine (2.5 mg/kg) plus the subthreshold dose of fluoxetine (15.0 mg/kg). Finasteride cancelled the antidepressant-like actions of the several combinations used. It is concluded that olanzapine alone or combined with fluoxetine or estradiol reduced immobility by increasing swimming. In conclusion, olanzapine produces antidepressant-like actions alone or in combination with estradiol. These antidepressant-like actions of this combination were cancelled by finasteride.     

Olanzapine counteracts stress-induced anxiety-like behavior in rats

Atypical antipsychotics, such as olanzapine, have been reported to display anxiolytic properties as shown in several preclinical and clinical studies. Furthermore, several experimental evidences have shown that olanzapine reduces fear and anxiety in activated anxiety-like behavior test such as Geller-Seifter test, ultrasonic vocalization test and stress-induced EtOH consumption. Here, we hypothesized that the anxiolytic action of olanzapine might be due to via an indirect activation of the γ-amino butyric acid (GABA)-ergic system through 3α-hydroxy-5α-pregnan-20-one [allopregnanolone (ALLO)], a potent neuroactive steroid that positively modulates the benzodiazepine-γ-aminobutyric acid type A (GABA_A)/benzodiazepine receptors complex. To address this question, we used a preclinical animal test to screen for novel anxiolytic compounds – the elevated plus-maze (EPM) – in basal condition and after 45 min restrain stress after acute or repeated (21 days) administration of olanzapine (0.5 mg/kg, i.p.). In this condition, we therefore study the effect of the 5-alpha-reductase inhibitor finasteride (FIN) (50 mg/kg) after co-administration with olanzapine. FIN is an inhibitor of steroidogenic enzymes which acts by inhibiting type II 5-alpha reductase, the enzyme that converts into 5-alpha-reduced metabolites like the GABA_A positive neuroactive steroid ALLO. Results showed an anxiolytic effect of the acute, but not of the chronic, treatment with olanzapine only in stressed rats. This anxiolytic effect was counteracted by the co-administration with FIN. These evidences suggest that the anxiolytic effects of olanzapine might be due to possible action of olanzapine on steroid function via activation of GABA system.     

Impairments in spatial learning and memory: ethanol, allopregnanolone, and the hippocampus

Acute ethanol administration impairs performance in many cognitive tasks that are dependent on hippocampal function. For example, acute ethanol administration produces dose-dependent impairments in spatial learning. Ethanol also decreases the spatial specificity of hippocampal place cells. Such findings raise the possibility that ethanol affects learning and memory by altering, either directly or indirectly, neuronal activity in the hippocampus and related structures.Acute ethanol administration induces a dose- and time-dependent increase in brain concentration of the neuroactive steroid allopregnanolone. Allopregnanolone is a potent GABA_A receptor agonist and produces effects similar to the effects produced by ethanol. Blockade of de novo biosynthesis of allopregnanolone alters many of ethanol's effects including ethanol-induced suppression of spontaneous activity in medial septum/diagonal band of Broca neurons and hippocampal pyramidal neurons. These findings suggest that ethanol-induced increases in allopregnanolone levels might play a central role in the effects of acute ethanol on cognitive processing and hippocampal function.The impact of ethanol on spatial cognitive processing and hippocampal function will be reviewed. In addition, the possibility that ethanol-induced changes in neuroactive steroid levels contribute to the impact of ethanol on spatial learning and hippocampal function will be explored.     

Neurosteroids infusion into the CA1 hippocampal region on exploration, anxiety-like behaviour and aversive learning

Neurosteroids (NS) are substances synthesised de novo in the brain that have rapid modulatory effects on ionotropic receptors. Specifically, NS can act as positive allosteric modulators of GABAA receptors as pregnanolone or allopregnanolone (Allop), or GABAA negative modulators and NMDA positive modulators as pregnenolone (PREG) or dehydroepiandrosterone (DHEA) and their sulphate esters (PREGS and DHEAS). Given this, their role in anxiety and emotional disturbances has been suggested. In addition, NS such as PREGS or DHEAS have demonstrated a promnesic role in several learning tests. The aim of the present work is to highlight the role that the dorsal (CA1) hippocampus plays in the behavioural profile of NS such as Allop and PREGS in tests assessing exploration, anxiety and aversive learning in rats. For this purpose, animals were administered intrahippocampally with Allop (0.2 μg/0.5 μl), PREGS (5 ng/0.5 μl) or vehicle in each hippocampus, and tested in the Boissier and elevated plus maze (EPM) tests. For learning test we have chosen the passive avoidance paradigm. Results indicate that intrahippocampal administration of Allop enhances exploration, reflected in an increase in the total and the inner number of head-dips. Allop-injected animals also showed an increase in the percentage of entries into the open arms of the EPM, suggesting an anxiolytic-like profile. In addition, post-acquisition PREGS administration enhanced passive avoidance retention, while post-acquisition Allop administration had no effects on aversive learning retention. These results point out the important role of the dorsal (CA1) hippocampus in several NS behavioural effects, such as exploration, anxiety, learning and memory.