López E, Arce C, Vicente S, Oset-Gasque M J, González M P
Instituto de Bioquímica (Centro Mixto CSIC-UCM), Facultad de Farmacia, Ciudad Universitaria, 28040 Madrid, Spain.
Cereb Cortex. 2001 Feb;11(2):158-63. doi: 10.1093/cercor/11.2.158.
Nicotine stimulation of cortical neurons obtained from gestation day 19 rats provoked a dose-dependent release of aspartate, glutamate, glycine and GABA, indicating a functional role for the nicotinic receptor in this model. This release was exclusively Ca2+-dependent (vesicular release) in the case of aspartate and dual Ca2+-dependent and Ca2+-independent) for glutamate, glycine and GABA. Nicotine also raised the membrane potential and the intracellular calcium concentration. These effects were specific, since they were reversed by hexamethonium, an antagonist of the nicotinic receptor. It was shown that L, N, and P/Q type Ca2+ channels are involved in nicotine-mediated Ca2+ entry into cortical neurons. Evaluation of the effects of nicotine on Ca2+ entry in isolated cells showed that 100% of the cells responded to nicotine, although the intensity of the response was variable: 63% of the neurons showed an increase in intracellular Ca(2+) of 152 +/- 5 grey levels, 25% of 88 +/- 12 grey levels and 12% of 48 +/- 1 grey levels. Tetrodotoxin, which blocks voltage-dependent Na(+) channels, completely reversed nicotine-induced Ca2+ entry into single cells. This suggests that the Ca2+ increment is mediated by opening of Ca2+ channels and not by the nicotinic receptor.
对取自妊娠第19天大鼠的皮层神经元给予尼古丁刺激，会引起天冬氨酸、谷氨酸、甘氨酸和γ-氨基丁酸呈剂量依赖性释放，这表明在该模型中烟碱型受体具有功能性作用。就天冬氨酸而言，这种释放完全依赖Ca2+（囊泡释放），而谷氨酸、甘氨酸和γ-氨基丁酸的释放则同时依赖Ca2+和不依赖Ca2+。尼古丁还会提高膜电位和细胞内钙浓度。这些效应具有特异性，因为它们可被烟碱型受体拮抗剂六甲铵逆转。研究表明，L型、N型和P/Q型Ca2+通道参与尼古丁介导的Ca2+进入皮层神经元的过程。对尼古丁对分离细胞中Ca2+内流的影响进行评估显示，尽管反应强度各不相同，但100%的细胞对尼古丁有反应：63%的神经元细胞内Ca2+增加了152±5灰度级，25%的增加了88±12灰度级，12%的增加了48±1灰度级。可阻断电压依赖性Na(+)通道的河豚毒素完全逆转了尼古丁诱导的Ca2+进入单细胞的过程。这表明Ca2+的增加是由Ca2+通道开放介导的，而非烟碱型受体。
