Guilbaud G, Benoist J M, Condes-Lara M, Gautron M
Unité de Recherches de Physiopharmacologie du Système nerveux, U 161 INSERM, Paris, France.
Somatosens Mot Res. 1993;10(3):229-44. doi: 10.3109/08990229309028834.
In this electrophysiological study, the responsiveness of neurons in the primary somatosensory cortex (SmI) was analyzed in rats with carrageenin-induced hyperalgesia for 24 hr. The functional implication of some changes in neuronal activity was improved in a few cases by a pharmacological test with Xylocaine injection in or close to the neuronal receptive field (RF), or with systemic aspirin. Unit recordings were performed alternately in the SmI cortex contralateral (Cc) or ipsilateral (Ci) to the inflamed hindpaw. In 29 rats with hyperalgesia tested prior to the recording session, 218 cells (128 in the Cc, 90 in the Ci) were tested with mechanical stimuli. In each SmI cortex, about 50% of them were driven by the stimulus. The "nonresponsive" neurons exhibited a higher firing rate in the Cc than in the Ci. The "responsive" (i.e., the somatosensory) neurons were classified according to their response to light touch, pinch, or joint movement. There was a highly significant difference between the two cortices, essentially because of the high proportion of "joint" Cc neurons (27 of 73 [37%] of the somatosensory neurons in the Cc, vs. only 8 of 47 [17%] in the Ci). "Light touch" neurons (41 of 73 [56%] in the Cc, vs. 35 of 47 [74.5%] in the Ci) had small RFs contralateral to the recording site. Of the 41 Cc cells of this type, 23 did not exhibit the classical characteristics of "light touch" cells; in particular, they exhibited striking discharges triggered by the stimulus but outlasting the stimulus duration, or occurring without intentional stimulation. These abnormal discharges were depressed or suppressed by injection of a local anesthetic (Xylocaine) in or close to the neuronal RF. "Pinch" neurons were very rare (5 of 73 [7%] in the Cc, vs. 4 of 47 [8.5%] in the Ci). Responses elicited from the inflamed paw were more pronounced than those from the noninflamed paw. "Joint" neurons were more numerous in the Cc than in the Ci. In addition, their responses obtained from contralateral RFs, and therefore from the inflamed paw, were more sustained than Ci responses elicited from the noninflamed paw. Afterdischarges of Ce neuronal responses and spontaneous paroxysmal activity were common on this side and were depressed by local anesthetic (Xylocaine) in their RFs or by systemic aspirin. These electrophysiological data emphasize the implication of SmI cortex in inflammatory hyperalgesia and more generally in pain processing.(ABSTRACT TRUNCATED AT 400 WORDS)
在这项电生理研究中，分析了角叉菜胶诱导的痛觉过敏24小时的大鼠初级体感皮层（SmI）中神经元的反应性。在少数情况下，通过在神经元感受野（RF）内或其附近注射利多卡因或给予全身性阿司匹林进行药理学测试，改善了神经元活动中一些变化的功能意义。在与发炎后爪对侧（Cc）或同侧（Ci）的SmI皮层中交替进行单位记录。在记录前测试的29只患有痛觉过敏的大鼠中，用机械刺激测试了218个细胞（Cc中128个，Ci中90个）。在每个SmI皮层中，约50%的细胞由刺激驱动。“无反应”神经元在Cc中的放电率高于Ci。“有反应”（即体感）神经元根据其对轻触、捏或关节运动的反应进行分类。两个皮层之间存在高度显著差异，主要是因为“关节”Cc神经元的比例很高（Cc中73个体感神经元中有27个[37%]，而Ci中47个中只有8个[17%]）。“轻触”神经元（Cc中73个中有41个[56%]，Ci中47个中有35个[74.5%]）在记录部位对侧的RF较小。在这41个Cc型细胞中，23个没有表现出“轻触”细胞的经典特征；特别是，它们表现出由刺激触发但持续时间超过刺激持续时间的明显放电，或者在没有故意刺激的情况下发生。通过在神经元RF内或其附近注射局部麻醉剂（利多卡因），这些异常放电被抑制或减弱。“捏”神经元非常罕见（Cc中73个中有5个[7%]，Ci中47个中有4个[8.5%]）。来自发炎爪子的反应比来自未发炎爪子的反应更明显。“关节”神经元在Cc中比在Ci中更多。此外，从对侧RF获得的反应，因此来自发炎爪子的反应，比从未发炎爪子引出的Ci反应更持久。Ce神经元反应的后放电和自发阵发性活动在这一侧很常见，并被其RF中的局部麻醉剂（利多卡因）或全身性阿司匹林抑制。这些电生理数据强调了SmI皮层在炎症性痛觉过敏以及更普遍的疼痛处理中的作用。（摘要截短至400字）
