Schlicker E, Werthwein S, Kathmann M, Bauer U
Institut für Pharmakologie und Toxikologie, Universität Bonn, Germany.
Naunyn Schmiedebergs Arch Pharmacol. 1998 Oct;358(4):418-22. doi: 10.1007/pl00005273.
A fourth type of opioid receptor, termed ORL1, has been cloned and nociceptin (also known as orphanin FQ) has been identified as an endogenous ligand at this receptor. We examined whether nociceptin affects the release of noradrenaline in the brain. For this purpose, cerebral cortex slices from the mouse, rat or guinea-pig were preincubated with [3H]noradrenaline and then superfused with medium containing desipramine and rauwolscine. Tritium overflow was evoked electrically (0.3 Hz) or by introduction of Ca2+ 1.3 mM into Ca2+-free K+-rich (15 mM) medium. Nociceptin 1 microM reduced the electrically evoked tritium overflow from mouse, rat and guinea-pig brain cortex slices by 80, 71 and 36%, respectively. Naloxone 10 microM did not change the effect of nociceptin. All subsequent experiments were performed on mouse brain cortex slices and in the presence of naloxone 10 microM. The concentration-response curve of nociceptin (maximum inhibition by 80%, pEC50 7.5) was shifted to the right by the non-selective ORL1 receptor antagonist naloxone benzoylhydrazone and the selective ORL1 receptor antagonist [Phe1psi(CH2-NH)Gly2]-nociceptin(1-13)NH2 (pA2 6.6 and 7.2, respectively). Naloxone benzoylhydrazone did not affect the evoked overflow by itself whereas [Phe1psi(CH2-NH)Gly2]nociceptin(1-13)NH2 caused an inhibition by maximally 35% (pEC50 7.0; intrinsic activity alpha 0.45). The inhibitory effect of [Phe1psi(CH2-NH)Gly2]-nociceptin(1-13)NH2 was counteracted by naloxone benzoylhydrazone. Nociceptin also reduced the Ca2+-evoked tritium overflow in mouse brain cortex slices superfused in the presence of tetrodotoxin. This effect was also antagonized by naloxone benzoylhydrazone, which, by itself, did not affect the evoked tritium overflow. In conclusion, nociceptin inhibits noradrenaline release more markedly in the mouse than in the rat or guinea-pig brain cortex. The effect of nociceptin in the mouse brain cortex involves ORL1 receptors, which are located presynaptically on noradrenergic neurones.
第四种阿片受体，称为ORL1，已被克隆，并且孤啡肽（也称为孤啡肽FQ）已被确定为该受体的内源性配体。我们研究了孤啡肽是否影响大脑中去甲肾上腺素的释放。为此，将来自小鼠、大鼠或豚鼠的大脑皮层切片与[3H]去甲肾上腺素预孵育，然后用含有地昔帕明和萝芙木碱的培养基进行灌流。通过电刺激（0.3Hz）或向无钙高钾（15mM）培养基中加入1.3mM Ca2+来诱发氚溢出。1μM孤啡肽分别使小鼠、大鼠和豚鼠大脑皮层切片中电诱发的氚溢出减少80%、71%和36%。10μM纳洛酮不改变孤啡肽的作用。所有后续实验均在小鼠大脑皮层切片上并在10μM纳洛酮存在的情况下进行。孤啡肽的浓度-反应曲线（最大抑制率80%，pEC50 7.5）被非选择性ORL1受体拮抗剂纳洛酮苯甲酰腙和选择性ORL1受体拮抗剂[Phe1ψ(CH2-NH)Gly2]-孤啡肽(1-13)NH2（pA2分别为6.6和7.2）向右移动。纳洛酮苯甲酰腙本身不影响诱发的溢出，而[Phe1ψ(CH2-NH)Gly2]孤啡肽(1-13)NH2最大可引起35%的抑制（pEC50 7.0；内在活性α 0.45）。[Phe1ψ(CH2-NH)Gly2]-孤啡肽(1-13)NH2的抑制作用被纳洛酮苯甲酰腙抵消。孤啡肽还减少了在河豚毒素存在下灌流的小鼠大脑皮层切片中Ca2+诱发的氚溢出。这种作用也被纳洛酮苯甲酰腙拮抗，纳洛酮苯甲酰腙本身不影响诱发的氚溢出。总之，孤啡肽在小鼠中比在大鼠或豚鼠大脑皮层中更明显地抑制去甲肾上腺素释放。孤啡肽在小鼠大脑皮层中的作用涉及ORL1受体，这些受体位于去甲肾上腺素能神经元的突触前。
