Van Vliet B J, Mulder A H, Schoffelmeer A N
Department of Pharmacology, Medical Faculty, Free University, Amsterdam, The Netherlands.
J Neurochem. 1990 Oct;55(4):1274-80. doi: 10.1111/j.1471-4159.1990.tb03135.x.
The receptors mediating the inhibition of D1 dopamine receptor-stimulated adenylate cyclase by opioids were examined in primary cultures of rat neostriatal neurons. Adenylate cyclase activity was dose-dependently increased by the selective D1 dopamine receptor agonist SKF 38393 (EC50 = 0.05 microM). This stimulation was fully antagonized by the selective D1 dopamine receptor antagonist SCH 23390 (1 microM). SKF 38393 (1 microM)-stimulated adenylate cyclase activity was strongly reduced (by almost 60%) by the highly selective mu-agonist [D-Ala2, MePhe4, Gly-ol5]-enkephalin (DAGO; EC50 = 0.006 microM) and high concentrations of the selective delta-agonist [D-Ser2(O-tert-butyl), Leu5]-enkephalyl-Thr6 (DSTBU-LET; EC50 = 0.13 microM) but not by the selective delta-agonist [D-penicillamine2, D-penicillamine5]enkephalin (DPDPE). D1 dopamine receptor-stimulated adenylate cyclase activity was also slightly reduced (by approximately 20%) by high concentrations of the kappa-agonist U50,488 (EC50 = 0.63 microM). The inhibitory effects of submaximally effective concentrations of DAGO, DSTBULET, and U50,488 were equally well antagonized by the mu-opioid receptor-selective antagonist naloxone (EC50 of approximately 0.1 microM). Neither the irreversible delta-ligand fentanyl isothiocyanate (1 microM) nor the reversible delta-antagonist ICI 174864 (1 microM) reversed the inhibitory effects of DSTBULET. The inhibitory effects of DAGO and U50,488 were equally well reversed by high concentrations (greater than 0.1 microM) of the kappa-opioid receptor-selective antagonist norbinaltorphimine. The effect of DAGO (1 microM) was already detectable after 1 day in culture, whereas DPDPE (1 microM) had no effect even after 28 days in culture. These data indicate that an homogeneous population of mu-opioid receptors coupled as inhibitors to D1 dopamine receptor-stimulated adenylate cyclase is expressed in rat neostriatal neurons in primary culture.
在大鼠新纹状体神经元的原代培养物中，研究了介导阿片类物质对D1多巴胺受体刺激的腺苷酸环化酶抑制作用的受体。选择性D1多巴胺受体激动剂SKF 38393（EC50 = 0.05微摩尔）可使腺苷酸环化酶活性呈剂量依赖性增加。这种刺激作用被选择性D1多巴胺受体拮抗剂SCH 23390（1微摩尔）完全拮抗。高选择性的μ激动剂[D-丙氨酸2，甲硫氨酸4，甘醇5]-脑啡肽（DAGO；EC50 = 0.006微摩尔）和高浓度的选择性δ激动剂[D-丝氨酸2（O-叔丁基），亮氨酸5]-脑啡肽-苏氨酸6（DSTBU-LET；EC50 = 0.13微摩尔）可使SKF 38393（1微摩尔）刺激的腺苷酸环化酶活性大幅降低（近60%），但选择性δ激动剂[D-青霉胺2，D-青霉胺5]脑啡肽（DPDPE）则无此作用。高浓度的κ激动剂U50,488（EC50 = 0.63微摩尔）也可使D1多巴胺受体刺激的腺苷酸环化酶活性略有降低（约20%）。亚最大有效浓度的DAGO、DSTBULET和U50,488的抑制作用同样被μ阿片受体选择性拮抗剂纳洛酮（EC50约为0.1微摩尔）拮抗。不可逆的δ配体异硫氰酸芬太尼（1微摩尔）和可逆的δ拮抗剂ICI 174864（1微摩尔）均不能逆转DSTBULET的抑制作用。高浓度（大于0.1微摩尔）的κ阿片受体选择性拮抗剂norbinaltorphimine可同样有效地逆转DAGO和U50,488的抑制作用。培养1天后即可检测到DAGO（1微摩尔）的作用，而DPDPE（1微摩尔）即使在培养28天后也无作用。这些数据表明，在原代培养的大鼠新纹状体神经元中，存在一类作为抑制剂与D1多巴胺受体刺激的腺苷酸环化酶偶联的同质性μ阿片受体。
