大鼠小直径痛觉三叉神经节神经元同时存在三磷酸肌醇敏感性钙库和阿诺碱敏感性钙库？P2X和P2Y嘌呤受体介导细胞内钙信号转导通路的变化

背景： 面部创伤或面部手术等可能损伤三叉神经系统而导致三叉神经疼痛，由于其疼痛剧烈难忍、易复发，长期以来一直为口腔临床治疗的一大难题。现有大量研究发现嘌呤类受体与三叉神经痛相关，目前对其作用机制知之甚少。 目的：探讨在小直径三叉神经节神经元中嘌呤类受体介导钙信号途径。 方法：用Fura-2荧光染料通过显微镜荧光测定技术实时检测急性分离成年大鼠小直径三叉神经节神经元的细胞内钙离子浓度。 结果：用正常外液或去除细胞外Ca2+灌流细胞，分别给予thapsigargin（1 μmol/L），内质网钙泵ATP酶抑制剂，和咖啡因（20 mmol/L），ryanodine受体激动剂，均能够引起细胞内游离钙离子浓度（Ca2+]i）不同程度地升高。ATP（100 μmol/L）也能够产生类似的效应。在去除细胞外Ca2+条件下，ATP引起的Ca2+]i升高可被thapsigargin可逆性地抑制，而不能被咖啡因抑制；然而在正常外液环境中，ATP引起的细胞内Ca2+]i 升高不能完全地被thapsigargin抑制。 结论：在痛觉三叉神经节神经元中，嘌呤类受体介导的Ca2+]i升高有两条途径，一种途径是通过代谢型P2Y受体作用于三磷酸肌醇敏感性钙库；另一种途径是通过离子型受体P2X受体引起外钙内流。

Changes in P2Y purinoreceptor-mediated intracellular calcium signal pathways results in inositol-1, 4, 5-triphosphate-sensitive calcium stores in rat small trigeminal ganglion neurons

BACKGROUND: Most of the currently available information on purinergic receptors (P2Rs) involved in pain transmission is based on results obtained in dorsal root ganglion or the spinal cord. However, the mechanism of P2Rs in trigeminal neuralgia remains unclear. OBJECTIVE: To investigate changes in the P2R-mediated calcium signaling pathway in nociceptive trigeminal ganglion neurons. DESIGN, TIME AND SETTING: In vitro experiments were conducted at the Patch-Clamp Laboratory of Comprehensive Experiment Center of Anhui Medical University, China from September 2008 to June 2009. MATERIALS: Thapsigargin, caffeine, suramin, and adenosine 5'-triphosphate were purchased from Sigma, USA. METHODS: Using Fura-2-based microfluorimetry, intracellular calcium concentration (Ca2+]i) was measured in freshly isolated adult rat small trigeminal ganglion neurons before and after drug application. MAIN OUTCOME MEASURES: Fluorescent intensities were expressed as the ratio F340/F380 to observe Ca2+]i changes. RESULTS: In normal extracellular solution and Ca2+-free solution, application of thapsigargin (1 μmol/L), a sarcoplasmic reticulum Ca2+ pump adenosine 5'-triphosphate inhibitor, as well as caffeine (20 mmol/L), a ryanodine receptor agonist, triggered Ca2+]i increase in small trigeminal ganglion neurons. A similar response was induced by application of adenosine 5'-triphosphate (100 μmol/L). In Ca2+-free conditions, adenosine 5'-triphosphate-induced Ca2+]i transients in small trigeminal ganglion neurons were inhibited in cells pre-treated with thapsigargin (P < 0.01), but not by caffeine (P > 0.05). In normal, extracellular solution, adenosine 5'-triphosphate-induced Ca2+]i transients in small trigeminal ganglion neurons were partly inhibited in cells pre-treated with thapsigargin (P < 0.05).CONCLUSION: Inositol-1, 4, 5-triphosphate (IP3)- and ryanodine-sensitive Ca2+ stores exist in rat nociceptive trigeminal ganglion neurons. Two pathways are involved in the purinoreceptor-mediated Ca2+]i rise observed in nociceptive trigeminal ganglion neurons. One pathway involves the metabotropic P2Y receptors, which are associated with the IP3 sensitive Ca2+store, and the second pathway is coupled to ionotropic P2X receptors that induce the Ca2+ influx.