皮质酮对大鼠海马神经元电压门控性钙通道及其突触活动的影响

目的　研究皮质酮对海马神经元电压门控性钙通道和突触活动的影响 ,以阐明其作用机理。方法　以培养的新生大鼠海马神经元为标本 ,使用膜片钳技术的全细胞记录方式 ,通过压力注射给药的方法观察皮质酮对神经元电压门控性钙通道及其自发性突触活动的影响。结果　皮质酮 1、10和 10 0μmol·L- 1可使神经元电压门控性钙电流的幅度分别增加 (14± 8) %、(41± 13) %和 (5 8± 9) % ,其增强效应具有明显的浓度依赖性特征 ,但没有电压依赖性 ,也不改变钙通道的电学特征。 10 0 μmol·L- 1皮质酮可使海马神经元突触活动的发生频率增加约 4倍。在使用河豚毒素阻断神经元的突触传递活动后 ,皮质酮仍然可以诱发低频 (4.6± 1.0 )Hz低幅 (0 .18±0 .0 9)nA的兴奋性突触后电流。结论　皮质酮对海马神经元电压门控性钙电流及其突触活动有明显的增强作用。皮质酮的即刻增强效应可能与其调节基因表达的作用无关。

Effects of corticosterone on voltage-gated calcium channel and spontaneous synaptic activities in cultured hippocampal neurons from neonatal rat

AIM Investigating the effects of corticosterone on the voltage- gated calcium channel and synaptic transmission in the cultured hippocampal neurons to clarify the reasonable mechanisms. METHODS The cultured hippocampal neurons from neonatal rats were served as preparation. The effect of corticosterone on the voltage-gated calcium channel and synaptic activity was observed by using whole-cell recording technique just after corticosterone was administrated by a pressure ejector. RESULTS The amplitudes of voltage gated calcium currents were increased (14±8)%, (41±13)% and (58±9)%, when 1, 10 and 100 μmol·L^-1 of corticosterone was applied, respectively. The potentiation was concentration-dependent, but voltage- independent. The characteristics of calcium channel were not influenced. Corticosterone (100 μmol·L^-1) increased the frequency of spontaneous synaptic activity to about 4- fold of the control. Excitatory synaptic currents with low frequency 〔(4.6±1.0)Hz〕 and small amplitude 〔(0.18±0.09)nA〕 could be still elicited by corticosterone in the presence of tetrodotoxin. CONCLUSION Corticosterone facilitated the voltage-gated calcium current and the synaptic transmission in the cultured hippocampal neurons. The immediate potentiation excluded the possibility that the gene modulation of corticosterone was involved.