Calejesan A A, Kim S J, Zhuo M
Department of Anesthesiology, Washington University Medical Center, Washington University in St. Louis, St. Louis, MO, 63110, USA.
Eur J Pain. 2000;4(1):83-96. doi: 10.1053/eujp.1999.0158.
It is well documented that the descending endogenous analgesia system, including the periaqueductal gray (PAG) and the rostral ventral medulla (RVM), play an important role in modulation of nociceptive transmission and morphine- and cannabinoid-produced analgesia. Neurons in the PAG receive inputs from different nuclei of higher structures, including the anterior cingulate cortex (ACC). However, it is unclear if stimulation of neurons in the ACC modulates spinal nociceptive transmission. The present study has examined the effects of electrical stimulation and chemical activation of metabotropic glutamate receptors (mGluRs) in the ACC on a spinal nociceptive tail-flick (TF) reflex induced by noxious heating. Activation of the ACC at high intensities (up to 500 microA) of electrical stimulation did not produce any antinociceptive effect. Instead, at most sites within the ACC (n = 36 of 41 sites), electrical stimulation produced significant facilitation of the TF reflex (i.e. decreases in TF latency). Chemical activation of mGluRs within the ACC also produced a facilitatory effect. Descending facilitation from the ACC apparently relays at the RVM. Electrical stimulation in the RVM produces a biphasic modulatory effect, showing facilitation at low intensities and inhibition at higher intensities. The present study provides evidence that activation of mGluRs within the ACC can facilitate spinal nociception.
有充分的文献记载，下行性内源性镇痛系统，包括导水管周围灰质（PAG）和延髓头端腹内侧区（RVM），在调节伤害性感受传递以及吗啡和大麻素产生的镇痛作用中发挥重要作用。PAG中的神经元接收来自包括前扣带回皮质（ACC）在内的不同高级结构核团的输入。然而，尚不清楚刺激ACC中的神经元是否会调节脊髓伤害性感受传递。本研究检测了ACC中电刺激和代谢型谷氨酸受体（mGluRs）的化学激活对有害热刺激诱发的脊髓伤害性甩尾（TF）反射的影响。高强度（高达500微安）电刺激ACC并未产生任何抗伤害感受作用。相反，在ACC内的大多数部位（41个部位中的36个），电刺激显著增强了TF反射（即TF潜伏期缩短）。ACC内mGluRs的化学激活也产生了促进作用。来自ACC的下行易化作用显然在RVM处中继。RVM中的电刺激产生双相调节作用，在低强度时表现为易化，在高强度时表现为抑制。本研究提供了证据表明ACC内mGluRs的激活可促进脊髓伤害感受。
