Involvement of ATP released from non-neuronal tlssues in presynaptic neuromodulation.

本课题组(04670132)在1992年至1993年间的研究结果总结如下：1.利用胞外核苷酸酶对非神经组织三磷酸腺苷释放代谢的影响用荧光素-荧光素酶测定法测定外源性三磷酸腺苷在豚鼠有、无输精管和回肠纵肌的浴液中的降解。在含有悬浮组织的介质中，浴液中的三磷酸腺苷含量在15min后以时间依赖的方式迅速下降到零。此外，在去甲肾上腺素和苯酚存在下，输精管和回肠段释放的三磷酸腺苷的衰变曲线几乎不受DFDNB和DFDNB等外源酶抑制剂的影响。DFDNB似乎能抑制由分泌剂引起的这些组织的三磷酸腺苷的释放。Cholingi…在豚鼠回肠纵肌上观察了α，β-亚甲基三磷酸腺苷(α，β-mATP)对电刺激神经诱发的内源性ACh释放的影响。用高效液相-电子捕获检测器测定ACh的释放量。电诱发的ACh释放可被α，β-mATP(3和30微米)所抑制，而在β_1受体拮抗剂茶碱(100微米)存在下，α，β-mATP(30微米)不能减少ACh的释放。ATP类似物以一种对苏拉明(P_2受体拮抗剂)敏感但对Ca~(2+)和阿托品不敏感的方式诱导血管内皮细胞释放ATP，提示P_2受体介导的ATP释放。这些结果表明，α，β-mATP不能通过直接刺激突触前P_1受体来减少ATP的释放，而且内源性的ATP类似物在突触后释放的ATP被代谢为突触内的腺苷，这种腺苷触发了对P_1-嘌呤受体敏感的胆碱能传递的神经调节。较少

The results obtained in my research project (04670132) during 1992 to 1993 are summarized as follows.Effects of inhibitors on metabolism by ectonucleotidases of ATP release from non-neuronal tissuesDegradation of exogenously applied ATP in the bathing solution with and without vas deferens and ileal longitudinal muscles of guinea pigs were measured by luciferin-luciferase assay. In medium with a suspended tissue, the amount of ATP in the bathing solution decreased quickly in a time-dependent manner to zero after 15 min. The decay curves of ATP were virtually unaffected by inhibitors of ecto-ATPase such as FSBA and DFDNB and by an ecto-5'-nucleotidase inhibitor, alpha, beta-methylene ADP.In addition, decay curves of ATP released from vas deferens and ileal segment in the presence of noradrenaline and bethanechol, respectively, were unchanged by inhibitors of these ectoenzymes except DFDNB.DFDNB seems to inhibit the release of ATP evoked by the secretagogues from these tissues.Cholinergi … More c neuromodulation evoked by ATP released from a non-neuronal tissueEffects of alpha, beta-methylene ATP (alpha, beta-mATP,a P_<2*>-receptor agonist) on endogenous ACh release evoked by electrical nerve stimulation were evaluated in guinea pig ileal longitudinal muscles. Release of ACh was measured with an HPLC-ECD system. Electrically evoked ACh release was reduced by alpha, beta-mATP at concentrations of 3 ad 30 muM.The reduction by alpha, beta-mATP (30 muM) was not observed in the presence of theophylline (100 muM), a P_1-receptor antagonist. The ATP analog induced the release of ATP in a suramin (P_2-receptor antagonist) -sensitive but Ca^<2+>-and atropine-insensitive manner, suggesting P_2-receptor-mediated release of ATP from the smooth muscle. We conclude from these findings that alpha, beta-mATP dose not reduce ATP release by direct stimulation of presynaptic P_1-receptors, and that endogenous ATP released postjunctionally by the ATP analog is decomposed metabolically to adenosine in the synaose and this adenosine triggers P_1-purinoceptor-sensitive neuromodulation of cholinergic transmission. Less