Calbindin neurons in the hamster suprachiasmatic nucleus do not exhibit a circadian variation in spontaneous firing rate
Calbindin neurons in the hamster suprachiasmatic nucleus do not exhibit a circadian variation in spontaneous firing rate
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DOI：
10.1046/j.1460-9568.2002.02309.x
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发表时间：
2002-12-01
影响因子：
3.4
通讯作者：
Allen, CN
中科院分区：
文献类型：
--
作者：
Jobst, EE;Allen, CN
哺乳动物视交叉上核(SCN)在行为和其他生理过程中产生昼夜节律的作用已得到证实。SCN神经元的一个显著特征是动作电位放电频率的昼夜振荡，在中午时分达到峰值。在仓鼠SCN内，一组钙结合蛋白免疫反应(CB+)神经元形成致密亚核(CBSN)。在SCN损伤的仓鼠中，使用胚胎SCN移植物恢复节律性严重依赖于移植物中CB+神经元的存在[LeSauter&Silver(1999)J.Neurosci.，5574-5585]。本研究的目的是确定仓鼠SCN的CBSN内的CB+神经元是否以昼夜节律的模式发射动作电位作为其输出信号的一部分。通过膜片钳记录，我们证明了体外昼夜条件下，CBSN内CB+神经元的自发放电频率不表现出昼夜节律。此外，沉默的CB-细胞的百分比随着时间的推移而变化，而沉默的CB+细胞的百分比不随时间变化。免疫组织化学分析显示，CBSN是一个不均匀的核，含有比CB+多得多的CB-细胞。我们的结果表明，CBSN内的CB+神经元代表着一个不同的神经元亚群，其中节律性动作电位输出可能不是恢复行为昼夜节律性所必需的。
The role of the mammalian suprachiasmatic nuclei (SCN) in generating circadian rhythms in behaviours and other physiological processes is well established. A prominent feature of SCN neurons is the circadian oscillation in action potential firing frequency, with a peak near midday. A subset of calbindin-immunoreactive (CB+) neurons form a compact subnucleus (CBsn) in the hamster SCN. Restoration of rhythmicity using fetal SCN grafts in SCN-lesioned hamsters is critically dependent upon the presence of CB+ neurons within the transplanted grafts [LeSauter & Silver (1999) J. Neurosci., 5574-5585]. The aim of the current study was to determine whether CB+ neurons within the CBsn of the hamster SCN fire action potentials in a circadian pattern as part of their output signal. Using patch-clamp recording, we demonstrated that CB+ neurons in the CBsn do not express a circadian rhythm in spontaneous firing frequency under diurnal conditions in vitro. Furthermore, the percentage of silent CB- cells varies with zeitgeber time, whereas the percentage of silent CB+ cells does not. Immunohistochemical analysis revealed that the CBsn is a nonhomogeneous nucleus, containing many more CB- than CB+ cells. Our results reveal that CB+ neurons within the CBsn represent a functionally distinct neuronal subpopulation in which rhythmic action potential output may not be necessary for the restoration of behavioural circadian rhythmicity.