Kapur A, Yeckel M, Johnston D
Division of Neuroscience, Baylor College of Medicine, One Baylor Plaza, Houston, TX 77030, USA.
Neuroscience. 2001;107(1):59-69. doi: 10.1016/s0306-4522(01)00293-7.
Mossy fiber activity can evoke Ca2+ release from internal stores in CA3 neurons, but the physiological conditions under which this occurs and the mechanisms underlying the release are not understood. Using rat hippocampal slices we report here that short trains of mossy fiber stimulation activate group I metabotropic glutamate receptors (mGluRs) on CA3 pyramidal neurons and elicit waves of Ca2+ release from inositol 1,4,5-trisphosphate (IP3) sensitive internal stores that propagate from stratum lucidum to the soma and in some cases distally out the dendrites. Activation of mGluR1,5 receptors by an agonist trans-azetidine-2,4-dicarboxylic acid (tADA) applied to stratum lucidum was also sufficient to induce waves of Ca2+ release. This release was blocked by internal heparin, but not by dantrolene, suggesting the involvement of IP3 rather than ryanodine receptors in not only the initial release but also in the maintenance of the propagating waves. Release could be facilitated by Ca2+ influx through voltage-gated Ca2+ channels, which is consistent with the known Ca2+ sensitivity of IP3 receptors.These results provide insight into the mechanisms and conditions of Ca2+ release in CA3 neurons and demonstrate the powerful influence mossy fiber input can have on these neurons.
苔藓纤维活动可诱发CA3神经元内储存库释放Ca2+，但发生这种情况的生理条件以及释放的潜在机制尚不清楚。我们在此利用大鼠海马切片报告，短串苔藓纤维刺激可激活CA3锥体神经元上的I组代谢型谷氨酸受体（mGluRs），并引发从1,4,5-三磷酸肌醇（IP3）敏感的内部储存库释放Ca2+的波，这些波从透明层传播到胞体，在某些情况下还向树突远端传播。将激动剂反式氮杂环丁烷-2,4-二羧酸（tADA）应用于透明层激活mGluR1、5受体也足以诱导Ca2+释放波。这种释放被内部肝素阻断，但不被丹曲林阻断，这表明不仅初始释放而且传播波的维持都涉及IP3受体而非兰尼碱受体。Ca2+通过电压门控Ca2+通道内流可促进释放，这与IP3受体已知的Ca2+敏感性一致。这些结果为CA3神经元中Ca2+释放的机制和条件提供了见解，并证明了苔藓纤维输入对这些神经元可能产生的强大影响。
