1Department of Neuroscience and Experimental Therapeutics, Texas A&M Health Science Center, College Station, Texas77843-1114, USA.
J Neurophysiol. 2009 Oct;102(4):2194-207. doi: 10.1152/jn.00301.2009. Epub 2009 Aug 12.
Alterations in neuronal Ca(2+) homeostasis are important determinants of age-related cognitive impairment. We examined the Ca(2+) influx, buffering, and electrophysiology of basal forebrain neurons in adult, middle-aged, and aged male F344 behaviorally assessed rats. Middle-aged and aged rats were characterized as cognitively impaired or unimpaired by water maze performance relative to young cohorts. Patch-clamp experiments were conducted on neurons acutely dissociated from medial septum/nucleus of the diagonal band with post hoc identification of phenotypic marker mRNA using single-cell RT-PCR. We measured whole cell calcium and barium currents and dissected these currents using pharmacological agents. We combined Ca(2+) current recording with Ca(2+)-sensitive ratiometric microfluorimetry to measure Ca(2+) buffering. Additionally, we sought changes in neuronal firing properties using current-clamp recording. There were no age- or cognition-related changes in the amplitudes or fractional compositions of the whole cell Ca(2+) channel currents. However, Ca(2+) buffering was significantly enhanced in cholinergic neurons from aged cognitively impaired rats. Moreover, increased Ca(2+) buffering was present in middle-aged rats that were not cognitively impaired. Firing properties were largely unchanged with age or cognitive status, except for an increase in the slow afterhyperpolarization in aged cholinergic neurons, independent of cognitive status. Furthermore, acutely dissociated basal forebrain neurons in which choline acetyltransferase mRNA was detected had the electrophysiological profiles of identified cholinergic neurons. We conclude that enhanced Ca(2+) buffering by cholinergic basal forebrain neurons may be important during aging.
神经元钙离子稳态的改变是与年龄相关的认知障碍的重要决定因素。我们检查了成年、中年和老年雄性 F344 行为评估大鼠基底前脑神经元的钙内流、缓冲和电生理学。相对于年轻队列，中年和老年大鼠的水迷宫表现被认为是认知受损或未受损的。在急性从中隔/斜角带核分离神经元的贴附细胞实验中，使用单细胞 RT-PCR 对表型标记物 mRNA 进行了事后鉴定。我们测量了全细胞钙和钡电流，并使用药物对这些电流进行了剖析。我们将 Ca(2+)电流记录与 Ca(2+)敏感比率荧光光度法相结合，以测量 Ca(2+)缓冲作用。此外，我们使用电流钳记录来寻找神经元放电特性的变化。全细胞 Ca(2+)通道电流的幅度或分数组成在年龄或认知相关方面没有变化。然而，来自认知受损的老年大鼠的胆碱能神经元的 Ca(2+)缓冲作用显著增强。此外，在认知未受损的中年大鼠中也存在 Ca(2+)缓冲作用的增加。除了在不依赖认知状态的情况下，老年胆碱能神经元中的慢后超极化增加外，年龄或认知状态对放电特性的影响不大。此外，急性分离的基底前脑神经元中检测到胆碱乙酰转移酶 mRNA 具有已鉴定的胆碱能神经元的电生理特征。我们得出结论，胆碱能基底前脑神经元增强的 Ca(2+)缓冲作用可能在衰老过程中很重要。
