The effects of anesthetics on spinal dorsal horn neuronal activity

脊髓背角宽动态范围（WDR）神经元对伤害性刺激反应的时相活动被麻醉药抑制。然而，麻醉剂对由强直性疼痛状态诱发的WDR神经元活性的影响，如在福尔马林试验中，还没有很好的理解。因此，我们检查了静脉内麻醉剂氯胺酮和噻苯丙氨酸1（3、10和30mg.kg、<-1>吸入麻醉剂异氟烷和氟烷（0.5%和1.5%）对福尔马林试验诱发的WDR神经元活性的影响。方法和结果：在去大脑、脊髓横断猫（L1-2）中，皮下（s.c.）将福尔马林注射液（0.05ml; 5.0%）置于后爪中脊髓WDR神经元的感受野中。这种注射在神经元中引起立即和持续的放电或活动爆发， ...更多信息 至少60分钟在注射福尔马林前5分钟，静脉注射硫代戊醛和氯胺酮以剂量依赖性方式抑制这种神经元放电。然而，当在注射福尔马林后5分钟给予硫代戊醛和氯胺酮时，对神经元放电的抑制作用显著较小。而异氟醚、氟烷等吸入麻醉药的超前给药与治疗后给药无明显差异。一个s.c.注射生理盐水0.05 ml）仅引起短暂的神经元兴奋，并且活动在1 -2 min内恢复到注射前水平。结果表明，注射福尔马林确实能在猫的脊髓背角产生连续的神经元活动爆发，此外，这种活性可以通过预先静脉内施用硫代戊醛和氯胺酮而显著降低。发现甲硫氨酸和氯胺酮抑制这种神经元反应的能力与福尔马林注射的时间有关，而吸入麻醉剂则没有。少

The phasic activity of wide dynamic range (WDR) neurons in the spinal dorsal horn in response to noxious stimulation is suppressed by anesthetics. However, the effects of anesthetics on the activity of WDR neurons that is evoked by a tonic pain state, as in the formalin test, are not well understood. Therefore, we examined the effects of intravenous anesthetics, ketamine and thiamyla1 (3, l0 and 30 mg.kg^<-1> inhalational anesthetics, isoflurane and halothane (0.5% and l.5%) on the activity of WDR neurons that is evoked by the formalin test. In addition, dose-response curves for thiamylal and ketamine were compared between preemptive administration and later administration.Methods and Results : In decerebrate, spinal cord-transected cats (L1-2), a subcutaneous (s.c.) injection of formalin (0.05 ml ; 5.0%) was placed in the receptive fields of spinal WDR neurons in the hind paw. This injection elicited an immediate and continuous discharge or burst of activity in the neurons that lasted … More for at least 60 minutes. Intravenous thiamylal and ketamine, administered 5 min prior to the injection of formalin inhibited this neuronal discharge in a dose-dependent manner. However, when thiamylal and ketamine was administered 5 min after the injection of formalin, the inhibitory effect on the neuronal discharge was significantly smaller. 1n contrast, preemptive administerted inhalatinal anesthetics, isoflurane and halothane did not different from the posttreatment administration. An s.c. injection of saline (0.05 ml) in the same receptive field elicited only transient neuronal excitation and the activity returned to the pre-injection level within l-2 min.Conclusions : The results suggest that an injection of formalin reliably produces a continuous burst of neuronal activity in the spinal dorsal horn of cats and, moreover, that this activity can be markedly reduced by the preemptive intravenous administration of thiamylal and ketamine. The ability of thiamylal and ketamine, but not inhalational anesthetics, to inhibit this neuronalresponse was found to be related to the timing of the formalin injection. Less