Elucidation of Mechanism of Pain Transmission by Gene Targeting

长期的炎症和神经损伤通常会导致慢性疼痛，因此，有害刺激会引起痛觉过敏，而无害的触觉刺激会引起疼痛(痛觉过敏)。随着分子生物学的出现，P物质和谷氨酸已被证明与急性疼痛和痛觉过敏有关，但与痛觉过敏有关的因子(S)尚不清楚。我们发现鞘内注射前列腺素E_2可引起清醒小鼠的痛觉异常，并建立了体内痛觉异常模型。近年来，我们通过使用受体激动剂和拮抗剂，从药理上阐明了痛觉过敏的机制。在此，我们将该模型应用于Lipocalin型前列腺素D合成酶缺乏症小鼠(L-PGDS)，并获得了以下结果：在L-PGDS-/-小鼠和野生型小鼠中，PGE_2和PGE_2都能诱导出痛敏反应，而在L-PGDS-/-小鼠中没有观察到PGE_2引起的痛觉过敏。同时给予毫微克量前列腺素D_2和前列腺素E_2诱发的L-前列腺素D_2-/-m…超敏反应更多的冰达到了与野生型老鼠相同的程度。这些结果表明，POD_2在PGE_2诱导的痛觉超敏中起重要作用。由于PGD_2在PG水平上阻断了PGE_2诱导的痛觉异常反应，所以这些用PGDS/-基因敲除小鼠的实验首次证明了PGD_2可能对PGE_2诱导的痛觉异常的诱导有双向调节作用。此外，抑制性氨基酸GABA介导了PGD_2的作用。目前，缺乏其他PG合成酶和PG受体的基因敲除小鼠的实验正在进行中。直到最近，人们普遍认为前列腺素作用于外周的疼痛传递，阿片类药物作用于中枢神经系统。借助于发育技术和基因定位技术，我们已经证明了pos和阿片类药物在分子水平上在诱发痛觉异常中起着重要作用。我们最近成功地从脑中分离出一种新的多肽nocistatin，其受体的克隆和鉴定正在进行中。较少

Prolonged inflammation and nerve injury often lead to chronic pain such that noxious stimuli evoke hyperalgesia and innocuous tactile stimuli evoke pain (allodynia). With the advent of molecular biology, substance P and glutamate have been shown to be involved in acute pain and hyperalgesia, but a factor(s) involving allodynia had remained to be known. We found that intrathecal administration of prostaglandin E_2 induced allodynia in conscious mice and established an in vivo allodynia model. These several years, we have pharmacologically elucidated the mechanism of allodynia by use of receptor agonists and antagonists. Here, we applied this model to mice lacking lipocalin-type PGD synthase (L-PGDS) and obtained following results.While hyperalgesia induced by PGD_2 and PGE_2 was observed in L-PGDS-/- mice as well as wild-type mice, PGE_2-induced allodynia was not observed in L-PGDS-/-. Simultaneous administration of a femtogram amount of PGD_2 with PGE_2 induced allodynia in L-PGDS-/- m … More ice to the same extent as in wild-type mice. These results demonstrate that POD_2 is essential for induction of PGE_2-induced allodynia. Because PGD_2 blocked PGE_2-induced allodynia at a pg level, these experiments with PGDS-/- knockout mice first demonstrate that PGD_2 may regulate the induction of PGE_2-induced allodynia biphasically. Furthermore, the inhibitory amino acid GABA was suggested to mediate the action of PGD_2. At present experiments with knockout mice lacking other PG synthases and PG receptors are under investigation. Until recently, it was generally accepted that PGs act on pain transmission in the periphery and that opioids act, in the central nervous system. With the aid of developmental technology and genetargeting techniques, we have shown that both POs and opioids play important roles in induction of allodynia at the molecular level. We have recently succeeded in isolation of a novel peptide nocistatin from the brain and the cloning and characterization of its receptor are in progress. Less