Ferchmin P A, Perez Dinely, Eterovic Vesna A, de Vellis Jean
Department of Biochemistry, Universidad Central Del Caribe, P.O. Box 60-327, Bayamon, Puerto Rico 00960-6032.
J Pharmacol Exp Ther. 2003 Jun;305(3):1071-8. doi: 10.1124/jpet.102.048173. Epub 2003 Mar 20.
Although in neuronal cultures nicotine was reported to prevent early and delayed excitotoxic death, no studies with nicotinic drugs have been done with acute hippocampal slices. We investigated the effect of nicotine and methyllycaconitine (MLA) on the toxicity of N-methyl-d-aspartate (NMDA) in the CA1 area of hippocampal slices. The excitotoxic effect of NMDA was assessed as decreased recovery of the capability to produce synaptically evoked population spikes (PSs). Application of nicotine or MLA before NMDA application increased the recovery of PSs. This electrophysiological recovery was used as a measure of the early neuroprotective events. The neuroprotection conferred by both nicotine and MLA was inhibited by dihydro-beta-erythroidine, showing mediation of neuroprotection by alpha 4 beta 2 neuronal nicotinic receptors (nAChRs). Because nicotine activates alpha 4 beta 2 and other nAChR subtypes, whereas 10 nM MLA inhibits the alpha 7 subtype, we propose the involvement of a neuronal circuitry-dependent mechanism for nicotinic neuroprotection. The effect of nicotine downstream from the receptors was investigated using inhibitors of cell signaling. The results suggest that the effect of nicotine is mediated by tyrosine receptor kinases, 1,2-phosphatidylinositol-3 kinase, and the mitogen-activated extracellular signal-regulated kinases. Although nicotine neuroprotection is Ca2+-dependent, neither L-type Ca2+ channels nor calmodulin-dependent protein kinase is involved in the effect of nicotine. In summary, these results suggest that in acute slices nicotinic protection is initiated either by direct activation of alpha 4 beta 2 or indirectly by inhibition of alpha 7 followed by signal transduction involving tyrosine kinases, phospholipid-dependent kinases, and mitogen-activated kinases.
尽管在神经元培养物中，据报道尼古丁可预防早期和延迟性兴奋性毒性死亡，但尚未对急性海马切片进行过烟碱类药物的研究。我们研究了尼古丁和甲基lycaconitine（MLA）对海马切片CA1区N-甲基-D-天冬氨酸（NMDA）毒性的影响。NMDA的兴奋性毒性作用通过突触诱发群体峰电位（PSs）产生能力的恢复降低来评估。在应用NMDA之前应用尼古丁或MLA可增加PSs的恢复。这种电生理恢复被用作早期神经保护事件的指标。二氢-β-刺桐啶可抑制尼古丁和MLA赋予的神经保护作用，表明α4β2神经元烟碱受体（nAChRs）介导了神经保护作用。由于尼古丁激活α4β2和其他nAChR亚型，而10 nM MLA抑制α7亚型，我们提出烟碱神经保护涉及神经元回路依赖性机制。使用细胞信号抑制剂研究了尼古丁在受体下游的作用。结果表明，尼古丁的作用由酪氨酸受体激酶、1,2-磷脂酰肌醇-3激酶和丝裂原活化的细胞外信号调节激酶介导。尽管尼古丁神经保护作用依赖于Ca2+，但L型Ca2+通道和钙调蛋白依赖性蛋白激酶均不参与尼古丁的作用。总之，这些结果表明，在急性切片中，烟碱保护作用要么通过直接激活α4β2启动，要么通过抑制α7间接启动，随后通过涉及酪氨酸激酶、磷脂依赖性激酶和丝裂原活化激酶的信号转导来实现。
