Womack M D, Walker J W, Khodakhah K
Department of Physiology & Biophysics, University of Colorado Health Sciences Center, Denver, Colorado 80262, USA.
J Gen Physiol. 2000 Mar;115(3):339-46. doi: 10.1085/jgp.115.3.339.
Cerebellar Purkinje neurons demonstrate a form of synaptic plasticity that, in acutely prepared brain slices, has been shown to require calcium release from the intracellular calcium stores through inositol trisphosphate (InsP(3)) receptors. Similar studies performed in cultured Purkinje cells, however, find little evidence for the involvement of InsP(3) receptors. To address this discrepancy, the properties of InsP(3)- and caffeine-evoked calcium release in cultured Purkinje cells were directly examined. Photorelease of InsP(3) (up to 100 microM) from its photolabile caged analogue produced no change in calcium levels in 70% of cultured Purkinje cells. In the few cells where a calcium increase was detected, the response was very small and slow to peak. In contrast, the same concentration of InsP(3) resulted in large and rapidly rising calcium responses in all acutely dissociated Purkinje cells tested. Similar to InsP(3), caffeine also had little effect on calcium levels in cultured Purkinje cells, yet evoked large calcium transients in all acutely dissociated Purkinje cells tested. The results demonstrate that calcium release from intracellular calcium stores is severely impaired in Purkinje cells when they are maintained in culture. Our findings suggest that cultured Purkinje cells are an unfaithful experimental model for the study of the role of calcium release in the induction of cerebellar long term depression.
小脑浦肯野神经元表现出一种突触可塑性形式，在急性制备的脑片中，已证明这种可塑性需要通过肌醇三磷酸（InsP(3)）受体从细胞内钙库释放钙。然而，在培养的浦肯野细胞中进行的类似研究几乎没有发现InsP(3)受体参与的证据。为了解决这一差异，直接检测了培养的浦肯野细胞中InsP(3)和咖啡因诱发的钙释放特性。从其光不稳定的笼形类似物中光释放InsP(3)（高达100 microM）在70%的培养浦肯野细胞中未引起钙水平变化。在少数检测到钙增加的细胞中，反应非常小且达到峰值缓慢。相比之下，相同浓度的InsP(3)在所有测试的急性解离浦肯野细胞中均导致大且快速上升的钙反应。与InsP(3)类似，咖啡因对培养的浦肯野细胞中的钙水平也几乎没有影响，但在所有测试的急性解离浦肯野细胞中诱发了大的钙瞬变。结果表明，当浦肯野细胞在培养中维持时，从细胞内钙库释放钙的过程严重受损。我们的研究结果表明，培养的浦肯野细胞是研究钙释放在小脑长时程抑制诱导中的作用的不可靠实验模型。
