Investigation on regulatory mechanism of acetylcholine release at cholinergic nerve endings.

为探讨胆碱能神经末梢上调节乙酰胆碱（ACh）释放的纳胆碱能受体亚型，用放射免疫分析法（RIA）直接测定了豚鼠回肠纵行肌条ACh释放。在各种实验条件下，将条与不可逆胆碱酯酶抑制剂一起预孵育，并用Kreds溶液灌注。哌仑西平（PZ）是一种特异性的M_1拮抗剂，其浓度比抑制电诱发的收缩反应的浓度低100倍，可使电诱发的ACh释放增加。另一方面，阿托品（AT），一种非特异性毒蕈碱拮抗剂，产生抑制突触前毒蕈碱受体的浓度比抑制突触后毒蕈碱受体的浓度低10倍。上述结果提示，豚鼠回肠中可能存在调节ACh释放的突触前M_1受体 ...更多信息 在同一制剂中，研究了不同浓度的nic拮抗剂对电诱发ACh释放和收缩反应的影响。选择性M_1受体拮抗剂替仑唑（TZ）可使电刺激引起的ACh释放增加，其浓度比抑制收缩反应的浓度低100倍。心脏选择性M_2激动剂AF-DX 116在10 μ M时抑制心肌收缩反应，但不影响电诱发的ACh释放。（-）N-甲基东莨菪碱（NMS）对收缩反应有抑制作用，但对ACh释放无影响。为探讨TRH对中枢神经系统ACh释放的影响，用放射免疫分析法测定了高钾（50 mM）诱发的大鼠基底前脑脑片ACh释放。TRH（100 μ M）引起钾诱发的ACh释放的轻微和统计学上不显著的增加。DN-1417，TRH类似物，在100 μ M浓度下显著增加钾诱发的ACh释放。这些发现表明DN-1417能够在高浓度下增加中枢神经系统中的ACh释放。少

To investigate subtypes of nuscarinic receptor regulating acetylcholine (ACh) release at cholinertic nerve endings, a radioimmunoassay (RIA) for ACh was applied to the direct determination of ACh release in longitudinal muscle strips of guinea pig ileum. The strips were preincubated with irreversible cholinesterase inhibitor and superfused with Kreds' solution under various experimental conditions. Pirenzepine (PZ), a specific M_1 antagonist, produced an increase in electrically evoked ACh release at a concentrtion of 100-times less than that inhibiting the electrically evoked contractile response. On the other hand, atropine (AT), a nonspecific muscarinic antagonist, produced an inhibition of presynaptic muscarinic receptors at a concentration of 10-fold less than that inhibiting postsynaptic muscarinic receptors. These results suggest that presyn aptic M_1 receptors regulating ACh release may be present in the guinea pig ileum.To confirm our previous data, the effect of three muscari … More nic antagonists on electrically evoked ACh release and contractile response were investigated in the same preparation. Telenzapine (TZ), a selective M_1 antagonist, increased electrically evoked ACh release at a concentration of 100-fold less than that inhiditing the contractile response. AF-DX 116, a cardioselective M_2 entagonist, inhibited the contractile response at 10 uM, but did not affect electrically evoked ACh release at this concentration. (-)N-Methylscopolamine (NMS) produced an inhibition of the contractile response without any effect on ACh release. The data-obtained in the present and previous studies demonstrate that presynaptic muscarinic receptors modulating ACh release can be classified as M_1 subtype.To examine effect of TRH on ACh release in the central nervous system, high potassium (50 mM)-evoked ACh release from rat basal forebrain slices was betermined using a RIA. TRH (100 uM) caused a slight and statistically insignificant increase in potassium-evoked ACh release. DN-1417, a TRH analogue, at a concentration of 100 uM increased potassium-evoked ACh release significantly. These findings indicate that DN-1417 is able to increase ACh release in the central nervous system at a high concentration. Less