Holland L N, Goldstein B D
Department of Pharmacology and Toxicology, Medical College of Georgia, Augusta 30912.
Brain Res. 1990 Dec 24;537(1-2):287-92. doi: 10.1016/0006-8993(90)90370-q.
Substance P (SP) has been proposed as a nociceptive transmitter/modulator in the dorsal horn of the spinal cord. Formalin used as a nociceptive stimulus has been shown to increase, in a biphasic manner, the amount of immunoreactive SP in the dorsal horn. The time course of the changes in substance P-like immunoreactivity (SPLI) caused by formalin is similar to both the electrical activity of dorsal horn neurons and licking behaviors. The administration of morphine reduces stereotypic behaviors caused by a formalin injection but actually increases the amount of SPLI in the dorsal horn. Therefore, the extent to which SP in the dorsal horn is involved with nociception as a result of formalin remains uncertain. To test the involvement of SP with chemogenic nociception, we utilized lidocaine to block afferent activity prior to an injection of formalin and studied the time course of behaviors and SPLI changes in the dorsal horn. Our results showed that formalin produced two distinct phases of nociceptive behaviors as measured by stereotypic licking of the injected paw: an acute 'phasic' response followed by a longer-lasting 'subacute' or 'tonic' response. Lidocaine reduced both phases of stereotypic behaviors, but only reduced the first increase of SPLI in the dorsal horn. These results suggested a direct involvement of SPLI in the dorsal horn with only 'phasic' behavioral responses to a formalin stimulus.
P物质（SP）被认为是脊髓背角中的一种伤害性递质/调质。用作伤害性刺激的福尔马林已被证明以双相方式增加脊髓背角中免疫反应性SP的量。福尔马林引起的P物质样免疫反应性（SPLI）变化的时间进程与脊髓背角神经元的电活动和舔舐行为相似。吗啡的给药减少了福尔马林注射引起的刻板行为，但实际上增加了脊髓背角中SPLI的量。因此，脊髓背角中的SP在多大程度上参与福尔马林引起的伤害感受仍不确定。为了测试SP与化学性伤害感受的关系，我们在注射福尔马林之前使用利多卡因阻断传入活动，并研究了行为和脊髓背角中SPLI变化的时间进程。我们的结果表明，通过注射爪的刻板舔舐测量，福尔马林产生了两个不同阶段的伤害性行为：急性“时相性”反应，随后是持续时间更长的“亚急性”或“紧张性”反应。利多卡因减少了刻板行为的两个阶段，但仅减少了脊髓背角中SPLI的首次增加。这些结果表明脊髓背角中的SPLI仅直接参与对福尔马林刺激的“时相性”行为反应。
