Hayashi T, Su T P, Kagaya A, Nishida A, Shimizu M, Yamawaki S
Cellular Pathobiology Unit, Molecular Neuropsychiatry Section, NIH/NIDA, Intramural Research Program, Baltimore, Maryland 21224, USA.
Synapse. 1999 Jan;31(1):20-8. doi: 10.1002/(SICI)1098-2396(199901)31:1<20::AID-SYN4>3.0.CO;2-2.
This study examined the effect of chronic antipsychotic treatment on the NMDA-elicited changes in intracellular free Ca2+ concentration ([Ca2+]i) in the primary culture of rat frontal cortical neurons. Antipsychotics used in the study were chosen for their differential affinities at dopamine D2 receptors and sigma receptors. The potential involvement of protein kinases in this action of antipsychotics were also examined. Chronic treatment of cells with antipsychotics (sulpiride, clozapine, and chlorpromazine) which are known to be potent dopamine D2 receptor ligands, whereas possessing low or no appreciable affinity for sigma receptors, caused a dose-dependent potentiation of the NMDA-induced increase in [Ca2+]i. On the contrary, haloperidol, which is as potent a sigma receptor ligand as a dopamine D2 receptor ligand, did not affect the NMDA-elicited increase in [Ca2+]i. Sulpiride increased the maximum effect afforded by different concentrations of NMDA and shifted the dose-response curve of NMDA to the left (EC50 value from 12.5 microM to 1.39 microM). Consistent with sulpiride's affinity at dopamine D2 receptors, this action of sulpiride was stereoselective: S(-)-sulpiride was active whereas R(+)-sulpiride was inactive. Treatment of cells with dopamine (3 microM) tends to decrease the NMDA-induced increase in [Ca2+]i. Sulpiride at 1 microM totally abolished this action of dopamine and restored its potentiating action on the NMDA-induced increase in [Ca2+]i. Haloperidol, a potent dopamine D2 and sigma receptor ligand, did not affect the sulpiride's potentiating action on the NMDA-induced responses. On the other hand, chronic treatment of cells with a sigma receptor agonist, DTG, at a concentration producing no effect of its own (10 nM), led to an enhancement of the potentiating effect of sulpiride on NMDA-induced increase in [Ca2+]i. This action of DTG was abolished by haloperidol. Further, chronic, but not acute, treatment of cells with either a protein kinase inhibitor H-7 or a cAMP-dependent protein kinase (PKA) inhibitor H-89 abolished this effect of sulpiride on the NMDA-induced [Ca2+]i changes. These results indicate that the action of NMDA in the primary cortical neurons are regulated differently by ligands with differential affinities at dopamine D2 and sigma receptors. The results with protein kinase inhibitors indicate that the potentiation of NMDA responses by sulpiride involves intracellular biochemical events.
本研究检测了慢性抗精神病药物治疗对大鼠额叶皮质神经元原代培养物中NMDA诱导的细胞内游离钙离子浓度（[Ca2+]i）变化的影响。本研究中使用的抗精神病药物因其对多巴胺D2受体和σ受体的不同亲和力而被选用。同时也检测了蛋白激酶在抗精神病药物这一作用中的潜在参与情况。用已知为强效多巴胺D2受体配体但对σ受体亲和力低或无明显亲和力的抗精神病药物（舒必利、氯氮平和氯丙嗪）对细胞进行慢性处理，导致NMDA诱导的[Ca2+]i增加呈剂量依赖性增强。相反，氟哌啶醇作为一种与多巴胺D2受体配体一样强效的σ受体配体，并不影响NMDA诱导的[Ca2+]i增加。舒必利增加了不同浓度NMDA产生的最大效应，并使NMDA的剂量-反应曲线向左移动（EC50值从12.5微摩尔降至1.39微摩尔）。与舒必利对多巴胺D2受体的亲和力一致，舒必利的这一作用具有立体选择性：S(-)-舒必利有活性而R(+)-舒必利无活性。用多巴胺（3微摩尔）处理细胞倾向于降低NMDA诱导的[Ca2+]i增加。1微摩尔的舒必利完全消除了多巴胺的这一作用，并恢复了其对NMDA诱导的[Ca2+]i增加的增强作用。氟哌啶醇作为一种强效多巴胺D2和σ受体配体，并不影响舒必利对NMDA诱导反应的增强作用。另一方面，用σ受体激动剂DTG以不产生自身效应的浓度（10纳摩尔）对细胞进行慢性处理，导致舒必利对NMDA诱导的[Ca2+]i增加的增强作用增强。DTG的这一作用被氟哌啶醇消除。此外，用蛋白激酶抑制剂H-7或环磷酸腺苷依赖性蛋白激酶（PKA）抑制剂H-89对细胞进行慢性而非急性处理，消除了舒必利对NMDA诱导的[Ca2+]i变化的这一效应。这些结果表明，NMDA在原代皮质神经元中的作用受到对多巴胺D2和σ受体具有不同亲和力的配体的不同调节。蛋白激酶抑制剂的结果表明，舒必利对NMDA反应的增强涉及细胞内生化事件。
