Pedata F, Magnani M, Pepeu G
Department of Preclinical and Clinical Pharmacology, University of Florence, Italy.
J Neurochem. 1988 Apr;50(4):1074-9. doi: 10.1111/j.1471-4159.1988.tb10575.x.
The release of 3H-labeled purines at rest and during electrical stimulation was investigated in slices of rat cortex prelabeled with [3H]adenine and perfused with Krebs solution. A linear relationship was found between radioactivity efflux and stimulation frequency from 2.5 to 20 Hz. At frequencies of less than 2.5 Hz, no increase in radioactivity efflux was detected. The amount of tritium released per pulse increased with stimulation frequency up to 10 Hz and declined at 20 Hz. The tritium efflux from the slices at rest and at a stimulation frequency of 10 Hz, analyzed by HPLC with ultraviolet absorbance detection at 254 nm, consisted mostly of adenosine, inosine, and hypoxanthine. The 3H-labeled purine release evoked by 10-Hz stimulation increased with current intensity from 15 to 100 mA/cm2. At 20 mA/cm2, addition of 0.5 microM tetrodotoxin to the superfusing Krebs solution brought about a 98% decrease of 3H-labeled purine release. At higher current strength, the percentage of tetrodotoxin-sensitive-evoked tritium efflux was smaller. At 30 mA/cm2, 86% of the evoked release was tetrodotoxin sensitive. Under these stimulation conditions, tritium efflux showed a 69% decrease when the slices were superfused with calcium-free Krebs solution containing 0.5 mM EGTA. The muscarinic agonist oxotremorine (30 microM) significantly enhanced the 10-Hz-stimulated 3H-labeled purine release. The effect of oxotremorine was partially prevented by tetrodotoxin, was antagonized by atropine (1.5 microM), and was mimicked by addition of physostigmine (3.8 microM) to the superfusion fluid. Atropine alone did not affect the evoked release, and none of the drugs modified the basal tritium efflux.(ABSTRACT TRUNCATED AT 250 WORDS)
在预先用[3H]腺嘌呤标记并灌注 Krebs 溶液的大鼠皮质切片中，研究了静息状态和电刺激期间 3H 标记嘌呤的释放情况。在 2.5 至 20Hz 的刺激频率范围内，发现放射性流出与刺激频率之间存在线性关系。在频率低于 2.5Hz 时，未检测到放射性流出增加。每个脉冲释放的氚量随刺激频率增加至 10Hz 而增加，并在 20Hz 时下降。通过在 254nm 处进行紫外吸收检测的高效液相色谱法分析，静息状态和 10Hz 刺激频率下切片中的氚流出主要由腺苷、肌苷和次黄嘌呤组成。10Hz 刺激引起的 3H 标记嘌呤释放随电流强度从 15 增加至 100mA/cm2 而增加。在 20mA/cm2 时，向灌注的 Krebs 溶液中添加 0.5μM 河豚毒素可使 3H 标记嘌呤释放减少 98%。在更高的电流强度下，河豚毒素敏感的诱发氚流出百分比更小。在 30mA/cm2 时，86%的诱发释放对河豚毒素敏感。在这些刺激条件下，当切片用含有 0.5mM EGTA 的无钙 Krebs 溶液灌注时，氚流出减少了 69%。毒蕈碱激动剂氧化震颤素（30μM）显著增强了 10Hz 刺激的 3H 标记嘌呤释放。氧化震颤素的作用部分被河豚毒素阻断，被阿托品（1.5μM）拮抗，并通过向灌注液中添加毒扁豆碱（3.8μM）模拟。单独的阿托品不影响诱发释放，并且这些药物均未改变基础氚流出。（摘要截断于 250 字）
