Hensler J G, Cotterell D J, Dubocovich M L
Department of Pharmacology, Northwestern University Medical School, Chicago, Illinois.
J Pharmacol Exp Ther. 1987 Dec;243(3):857-67.
Superfusion with dopamine (0.1 microM-10 mM) evokes calcium-dependent [3H]acetylcholine release from rabbit retina labeled in vitro with [3H]choline. This effect is antagonized by the D-1 dopamine receptor antagonist SCH 23390. Activation or blockade of D-2 dopamine, alpha-2 or beta receptors did not stimulate or attenuate the release of [3H]acetylcholine from rabbit retina. Dopamine receptor agonists evoke the release of [3H]acetylcholine with the following order of potency: apomorphine greater than or equal to SKF(R)82526 greater than SKF 85174 greater than SKF(R)38393 greater than or equal to pergolide greater than or equal to dopamine (EC50 = 4.5 microM) greater than SKF(S)82526 greater than or equal to SKF(S)38393. Dopamine receptor antagonists inhibited the dopamine-evoked release of [3H]acetylcholine: SCH 23390 (IC50 = 1 nM) greater than (+)-butaclamol greater than or equal to cis-flupenthixol greater than fluphenazine greater than perphenazine greater than trans-flupenthixol greater than R-sulpiride. The potencies of dopamine receptor agonists and antagonists at the dopamine receptor mediating [3H]acetylcholine release is characteristic of the D-1 dopamine receptor. These potencies were correlated with the potencies of dopamine receptor agonists and antagonists at the D-1 dopamine receptor in rabbit retina as labeled by [3H]SCH 23390, or as determined by adenylate cyclase activity. [3H]SCH 23390 binding in rabbit retinal membranes was stable, saturable and reversible. Scatchard analysis of [3H]SCH 23390 saturation data revealed a single high affinity binding site (Kd = 0.175 +/- 0.002 nM) with a maximum binding of 482 +/- 12 fmol/mg of protein. The potencies of dopamine receptor agonists to stimulate [3H]acetylcholine release were correlated with their potencies to stimulate adenylate cyclase (r = 0.784, P less than .05, n = 7) and with their affinities at [3H]SCH 23390 binding sites (r = 0.755, P greater than .05, n = 8). The potencies of antagonists to inhibit dopamine-evoked [3H]acetylcholine release were correlated with their potencies to inhibit the dopamine-stimulated adenylate cyclase (r = 0.759, P less than .05, n = 5) and with their affinities at [3H]SCH 23390 binding sites (r = 0.998, P less than .01, n = 7). We conclude that in rabbit retina dopamine evokes calcium-dependent [3H]acetylcholine release through activation of a site with the pharmacological characteristics of a D-1 dopamine receptor.
用多巴胺（0.1微摩尔/升 - 10毫摩尔/升）进行灌流，可促使经体外[3H]胆碱标记的兔视网膜释放钙依赖性[3H]乙酰胆碱。D - 1多巴胺受体拮抗剂SCH 23390可拮抗此效应。激活或阻断D - 2多巴胺、α - 2或β受体，均不会刺激或减弱兔视网膜[3H]乙酰胆碱的释放。多巴胺受体激动剂按以下效力顺序促使[3H]乙酰胆碱释放：阿扑吗啡≥SKF(R)82526＞SKF 85174＞SKF(R)38393≥培高利特≥多巴胺（半数有效浓度=4.5微摩尔/升）＞SKF(S)82526≥SKF(S)38393。多巴胺受体拮抗剂抑制多巴胺诱发的[3H]乙酰胆碱释放：SCH 23390（半数抑制浓度=1纳摩尔/升）＞(+)-布他拉莫≥顺式氟奋乃静＞氟奋乃静＞奋乃静＞反式氟奋乃静＞R - 舒必利。介导[3H]乙酰胆碱释放的多巴胺受体上，多巴胺受体激动剂和拮抗剂的效力具有D - 1多巴胺受体的特征。这些效力与[3H]SCH 23390标记的或通过腺苷酸环化酶活性测定的兔视网膜D - 1多巴胺受体上多巴胺受体激动剂和拮抗剂的效力相关。兔视网膜膜中[3H]SCH 23390结合稳定、可饱和且可逆。对[3H]SCH 23390饱和数据进行Scatchard分析，显示有一个单一的高亲和力结合位点（解离常数=0.175±0.002纳摩尔/升），最大结合量为482±12飞摩尔/毫克蛋白质。多巴胺受体激动剂刺激[3H]乙酰胆碱释放的效力，与其刺激腺苷酸环化酶的效力相关（r = 0.784，P＜0.05，n = 7），也与其在[3H]SCH 23390结合位点的亲和力相关（r = 0.755，P＞0.05，n = 8）。拮抗剂抑制多巴胺诱发的[3H]乙酰胆碱释放的效力，与其抑制多巴胺刺激的腺苷酸环化酶的效力相关（r = 0.759，P＜0.05，n = 5），也与其在[3H]SCH 23390结合位点的亲和力相关（r = 0.998，P＜0.01，n = 7）。我们得出结论，在兔视网膜中，多巴胺通过激活具有D - 1多巴胺受体药理学特征的位点，促使钙依赖性[3H]乙酰胆碱释放。
