ORPHANIN FQ (OFQ) EFFECTS ON RAT COLONIC MOTILITY

最近在大鼠脑内发现了内源性阿片受体样受体1(ORL1)配体--孤啡肽FQ(OFQ)，它是一种结构类似强啡肽A的十七肽。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，OFQ优先刺激大鼠结肠的肌肉收缩，而不影响上消化道的运动。我们已经证明，OFQ加速结肠运输，并唤起推进的结肠运动。相比之下，强啡肽A会延迟结肠运输，并产生非推进性运动。根据我们的初步研究，我们假设OFQ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ATP神经通路而引起收缩。抑制这一抑制神经通路将导致结肠肌肉收缩，加速结肠运输。相反，强啡肽A抑制ACh、SP、NO、VIP和PACAP的释放，刺激随机的非协调性肌肉收缩，导致结肠传输延迟。为了验证这一假设，我们计划进行免疫组织化学以证明OFQ在结肠肌间神经丛中大量存在，并通过原位杂交证明OFQ受体在结肠肌间神经丛中表达。然后，我们将描述负责OFQ对结肠运动的刺激作用的神经通路，并通过电生理学研究来研究介导抑制通路的细胞机制。最后，将通过药理学研究和免疫细胞化学鉴定OFQ抑制的神经递质。此外，我们还计划比较和对比OFQ和强啡肽A对结肠运动的作用机制。我们将证明，OFQ，而不是强啡肽A，在体内引起推进的结肠运动和加速结肠传输。强啡肽A抑制介导蠕动反射的ACh/SP/NO/VIP/PACAP通路，而不是OFQ。此外，我们将进行原位杂交和(免疫)组织化学相结合的程序，以证明OFQ受体存在于含ATP的神经元上，而Kappa受体存在于含ACh、SP、NOS、VIP或PACAP的神经元上。这些研究将有助于阐明OFQ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或其类似物可能对人类难治性便秘的治疗有利。

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.