大脑皮质体感区 C 类纤维诱发单位放电的胆碱能调制作用

CHOLINERGIC MODULATION OF THE C FIBER EVOKED DISCHARGES OF SINGLE NEURONS IN THE PRIMARY SOMATOSENSORY CORTEX

用微电泳技术研究乙酰胆碱（Ａｃｈ）及胆碱能受体阻断剂阿托品（Ａｔｒ）和六羟季胺（Ｃ６）对电刺激猫隐神经Ｃ类纤维诱发的大脑皮质体感Ⅰ区（ＳⅠ区）神经元单位放电（Ｃ－ＥＤ）的影响。结果表明，绝大部分Ｃ－ＥＤ单位（２２／２４）位于大脑皮质的深层；Ａｃｈ能明显抑制大部分单位（５／８）的Ｃ－ＥＤ，标准化互协方差函数（ＮＣＣＶＦ）积分值降低（Ｐ＜０．０５）；Ａｔｒ使大部分单位（１１／１７）的Ｃ－ＥＤ增强，ＮＣＣＶＦ积分值增加（Ｐ＜０．０５）；而Ｃ６使大部分单位（６／９）的Ｃ－ＥＤ减弱，ＮＣＣＶＦ积分值降低（Ｐ＜０．０５）。表明，Ｃ类纤维诱发的大脑皮质单位放电接受胆碱能调制，可能主要通过胆碱能Ｍ受体起抑制作用，还有胆碱能Ｎ受体的易化作用。提示Ａｃｈ在大脑皮质的神经元水平上也可能参与痛觉的调制。

The effects of iontophoretic application of acetylcholine(Ach) and cholinergic receptor blockers atropine(Atr) and hexamethonium(C 6) on the C fiber evoked discharge(C ED) of single neurons in the primary somatosensory cortex (SⅠ) were investigated in cats. Most of neurons (22/24) were located in the deep layer, 1000～2000μm below the cortical surface. Among most of the cells tested (5/8) the C ED was significantly suppresed when Ach was delivered, with a decrease in the mean integral value of normalized cross covariance function (NCCVF) from 0 5243±0.1293 to 0.3526±0.1910(P<0.05). The significant enhancement of C ED was observed in 11 out of 17 cells tested when Atr was ejected. The mean integral value of NCCVF was 0.4511±0.2742 compared with 0 3702±0.2436 in control (P<0.05). However, 6 of 9 cells tested decrease their C ED following C 6 application. The mean integral value of NCCVF decreased from 0.3014±0.1944 to 0.2073±0.1495(P<0.05). These studies suggest that C ED can be modulated by Ach. The suppression and enhancement effects of Ach may be predominantly mediated through muscarinic and nicotinic receptors, respectively. It also suggests that Ach may modulate the pain processing in the cerebral cortex level.