ORPHANIN FQ (OFQ) EFFECTS ON RAT COLONIC MOTILITY

内源性阿片样受体1（ORL 1）配体--强啡肽FQ（OFQ）是一种与强啡肽A结构相似的十七肽，最近在大鼠脑中被发现。 然而，OFQ在胃肠道（GI）中的生理作用尚不清楚。 我们的初步研究表明，孤啡肽优先刺激结肠肌肉收缩，而不影响上消化道的运动。 我们已经证明，孤啡肽加速结肠运输和唤起推进结肠运动。 相反，强啡肽A延迟结肠运输并产生非推进性运动。 基于我们的初步研究，我们假设孤啡肽作用于结肠肌间神经丛，并通过抑制结肠肌间神经丛的抑制性ATP神经通路而引起收缩。抑制这种抑制性神经通路将导致结肠肌肉收缩并加速结肠运输。 相反，强啡肽A抑制ACh、SP、NO、VIP和PACAP的释放，并刺激随机的非协调肌肉收缩，导致结肠运输延迟。 为了验证这一假设，我们计划进行免疫组化，以证明OFQ是存在于丰富的结肠肌间神经丛，并证明OFQ受体表达在结肠肌间神经丛的原位杂交。 然后，我们将表征负责孤啡肽对结肠运动的刺激作用的神经通路，并通过电生理学研究研究介导抑制抑制通路的细胞机制。 最后，将通过药理学研究以及免疫细胞化学来鉴定OFQ抑制的抑制性神经递质。 此外，我们还计划比较和对比OFQ与强啡肽A对结肠运动的作用机制。 我们将证明，OFQ，而不是强啡肽A，导致推进结肠运动，加速结肠运输在体内。强啡肽A抑制ACh/SP/NO/VIP/PACAP通路，而OFQ不抑制该通路。 此外，我们将执行原位杂交和（免疫）组织化学的组合程序，以证明OFQ受体存在于ATP含有神经元，而κ受体存在于ACh-，SP-，NOS-，VIP-，或PACAP-含有神经元。这些研究将有助于阐明孤啡肽和强啡肽A对结肠运动的作用机制。 这可能具有重要的临床意义，因为OFQ或其类似物可能有益于治疗人类难治性便秘。

The endogenous opioid receptor-like 1 (ORL1) ligand, orphanin FQ (OFQ), a heptadecapeptide structurally resembling dynorphin A, has recently been identified in rat brain. However, the physiological role of OFQ in gastrointestinal (GI) tract is unknown. Our preliminary studies have shown that OFQ preferentially stimulates muscular contraction in colon without affecting the motility of upper GI tract in rats. We have demonstrated that OFQ accelerates colonic transit and evokes propulsive colonic movements. In contrast, dynorphin A delays colonic transit and produces non-propulsive movements. Based on our preliminary studies, we hypothesized that OFQ acts on colonic myenteric plexus and causes contractions by inhibiting an inhibitory ATP neural pathway of the colonic myenteric plexus. Inhibition of this inhibitory neural pathway will result in colonic muscle contraction and accelerates colonic transit. In contrast, Dynorphin A inhibits ACh, SP, NO, VIP and PACAP release and stimulates random non-coordinated muscle contraction resulting in delayed colonic transit. To test this hypothesis, we plan to perform immunohistochemistry to demonstrate that OFQ is present in abundance in the colonic myenteric plexus and demonstrate that OFQ receptors are expressed in the colonic myenteric plexus by in situ hybridization. We will then characterize the neural pathways responsible for the stimulatory action of OFQ on colonic motility and investigate the cellular mechanism mediating the inhibition of an inhibitory pathway by electrophysiological studies. Finally, the inhibitory neurotransmitter inhibited by OFQ will be identified by pharmacological studies as well as immunocytochemistry. In addition, we also plan to compare and contrast the mechanisms of action of OFQ versus dynorphin A on colonic motility. We will demonstrate that OFQ, but not dynorphin A, causes propulsive colonic movements and accelerates colonic transit in vivo. Dynorphin A, but not OFQ, inhibits ACh/SP/NO/VIP/PACAP pathway which mediates the peristaltic reflex. In addition, we will perform combined procedure of in situ hybridization and (immuno)histochemistry to demonstrate that OFQ receptors are present on ATP containing neurons whereas kappa receptors are present on ACh-, SP-, NOS-, VIP-, or PACAP-containing neurons. These studies will shed light on the mechanisms of action of OFQ and dynorphin A on colonic motility. This may have important clinical implications since OFQ or its analogues may be beneficial for the treatment of refractory constipation in humans.