Velázquez R A, Kitto K F, Larson A A
Department of Veterinary PathoBiology, University of Minnesota, Saint Paul 55108, USA.
J Pharmacol Exp Ther. 1997 Jun;281(3):1231-7.
((2S,3S)-[cis-2-(diphenylmethyl)-N-[(2-methoxyphenyl)-methyl]-1-az abicyclo[2.2.2]octan-3-amine]) (CP-96,345) noncompetitively inhibits substance P (SP) binding at the neurokinin-1 (NK-1) site and has been widely used to determine the extent of NK-1 activity in nociception. To test the selectivity of this compound in vivo regarding other putative nociceptive transmitters, such as excitatory amino acids, we compared the actions of CP-96,345 to those of ((2R,3R)-[cis-2-(diphenylmethyl)-N-[(2-methoxyphenyl)-methyl]-1-az abicyclo[2.2.2]octan-3-amine]), a less active isomer, on behavioral responses induced by SP, N-methyl-D-aspartate (NMDA) and kainic acid (KA) injected intrathecally in mice. When injected intrathecally, SP, NMDA or KA produce a caudally directed biting and scratching behavior that lasted for approximately 60 to 90 sec. At a dose as high as 2 nmol, CP-96,345 had no effect on responses induced by a single injection of 22.5 pmol of SP. In contrast, NMDA-induced behaviors were inhibited by CP-96,345 in a dose-related fashion beginning at a dose as low as 0.02 nmol. There was also an inhibitory effect of CP-96,345 on KA-induced activity that was not dose related. The more potent inhibitor of [3H] SP binding, (+)-(2S,3S)-3-(2-methoxybenzylamino)-2-phenylpiperidine (CP-99,994), was approximately 10 times more potent in inhibiting NMDA-induced activity than CP-96,345. CP-99,994 also inhibited NMDA-induced activity at doses that failed to inhibit SP-induced behavior. Also attenuated by CP-96,345 was the development of sensitization to the behavioral effects produced by repeated injections of KA and desensitization to repeated injections of SP, phenomena linked to an action of the N-terminus of SP. NMDA-induced behaviors and sensitization to KA were found to be sensitive to verapamil, consistent with their mediation by calcium. These results indicate that either CP-96,345 and CP-99,994 do not inhibit NK-1-induced activity in the mouse spinal cord, or that exogenously administered SP does not induce behavioral responses by an interaction with NK-1 receptors. Whether CP-96,345 acts by a mechanism that involves inhibition of calcium channels and/or SP N-terminal activity requires further testing.
((2S,3S)-[顺式-2-(二苯甲基)-N-[(2-甲氧基苯基)-甲基]-1-氮杂双环[2.2.2]辛烷-3-胺]) (CP-96,345) 非竞争性抑制P物质 (SP) 在神经激肽-1 (NK-1) 位点的结合，并且已被广泛用于确定伤害感受中NK-1活性的程度。为了测试该化合物在体内对其他假定的伤害性递质（如兴奋性氨基酸）的选择性，我们比较了CP-96,345与活性较低的异构体 ((2R,3R)-[顺式-2-(二苯甲基)-N-[(2-甲氧基苯基)-甲基]-1-氮杂双环[2.2.2]辛烷-3-胺]) 对鞘内注射SP、N-甲基-D-天冬氨酸 (NMDA) 和 kainic 酸 (KA) 诱导的小鼠行为反应的作用。鞘内注射时，SP、NMDA或KA会产生持续约60至90秒的向尾咬和抓挠行为。在高达2 nmol的剂量下，CP-96,345对单次注射22.5 pmol SP诱导的反应没有影响。相比之下，CP-96,345以剂量相关的方式抑制NMDA诱导的行为，起始剂量低至0.02 nmol。CP-96,345对KA诱导的活性也有抑制作用，但与剂量无关。[3H] SP结合的更强效抑制剂(+)-(2S,3S)-3-(2-甲氧基苄基氨基)-2-苯基哌啶 (CP-99,994) 在抑制NMDA诱导的活性方面比CP-96,345强约10倍。CP-99,994在未能抑制SP诱导行为的剂量下也抑制了NMDA诱导的活性。对KA重复注射产生的行为效应的致敏作用以及对SP重复注射的脱敏作用（这些现象与SP的N末端作用有关）也被CP-96,345减弱。发现NMDA诱导的行为和对KA的致敏作用对维拉帕米敏感，这与其由钙介导一致。这些结果表明，要么CP-96,345和CP-99,994不抑制小鼠脊髓中NK-1诱导的活性，要么外源性给予的SP不通过与NK-1受体相互作用诱导行为反应。CP-96,345是否通过涉及抑制钙通道和/或SP N末端活性的机制起作用需要进一步测试。
