Okuhara D Y, Beck S G
Department of Pharmacology, Loyola University Chicago Stritch School of Medicine, Maywood, Ill 60153, USA.
Neuroendocrinology. 1998 Jan;67(1):58-66. doi: 10.1159/000054299.
Corticosteroids regulate gene expression through the activation of mineralocorticoid and glucocorticoid receptors. The hippocampus contains the highest density of mineralocorticoid and glucocorticoid receptors in the central nervous system. The modulation of neuron excitability by corticosteroids in hippocampal subfield CA1 is well documented. However, it is not known whether corticosteroids produce different effects across the various hippocampal subfields. Therefore, we used intracellular recording techniques to examine the actions of chronic corticosteroid treatment (2 weeks) on the electrophysiological properties of rat hippocampal subfield CA3 pyramidal cells. The treatment groups used in this investigation were: adrenalectomy (ADX), selective mineralocorticoid receptor activation with aldosterone (ALD), mineralocorticoid and glucocorticoid receptor activation with high levels of corticosterone (HCT), and SHAM. Corticosteroid treatment altered the percentage of nonburst and burst firing neurons. The percentages of nonbursting cells were 74 and 62% in tissue from ADX and HCT animals compared to 42 and 41% in ALD and SHAM animals, respectively. The corticosteroid-induced effect on the ratio of nonbursting to bursting cells does not appear to be secondary to changes in the cell's membrane input resistance, resting potential, time constant, action potential, slow-or fast-afterhyperpolarizing potential properties. Based on these results we conclude that corticosteroids are important for maintaining the ratio of nonburst and burst firing pyramidal neurons in subfield CA3. These novel results are distinct from those previously reported for subfield CA1, suggesting that corticosteroids have different effects across hippocampal subfields.
皮质类固醇通过激活盐皮质激素和糖皮质激素受体来调节基因表达。海马体在中枢神经系统中含有最高密度的盐皮质激素和糖皮质激素受体。皮质类固醇对海马体CA1亚区神经元兴奋性的调节作用已有充分记录。然而，目前尚不清楚皮质类固醇在不同的海马体亚区是否会产生不同的作用。因此，我们采用细胞内记录技术来研究慢性皮质类固醇治疗（2周）对大鼠海马体CA3亚区锥体细胞电生理特性的影响。本研究中使用的治疗组包括：肾上腺切除术（ADX）、用醛固酮（ALD）选择性激活盐皮质激素受体、用高水平皮质酮（HCT）激活盐皮质激素和糖皮质激素受体以及假手术组（SHAM）。皮质类固醇治疗改变了非爆发性和爆发性放电神经元的比例。ADX组和HCT组动物组织中的非爆发性细胞百分比分别为74%和62%，而ALD组和SHAM组动物中的非爆发性细胞百分比分别为42%和41%。皮质类固醇对非爆发性细胞与爆发性细胞比例的诱导作用似乎并非继发于细胞膜输入电阻、静息电位、时间常数、动作电位、慢或快后超极化电位特性的变化。基于这些结果，我们得出结论，皮质类固醇对于维持CA3亚区非爆发性和爆发性放电锥体细胞的比例很重要。这些新结果与先前报道的CA1亚区结果不同，表明皮质类固醇在不同的海马体亚区具有不同的作用。
