McKenna T M, Ashe J H, Hui G K, Weinberger N M
Center for the Neurobiology of Learning and Memory, University of California, Irvine 92717.
Synapse. 1988;2(1):54-68. doi: 10.1002/syn.890020109.
The present experiments studied the effects of cholinergic agonists and antagonists on the spontaneous and acoustic-evoked discharge of auditory cortical neurons and examined whether these effects were mediated by muscarinic cholinergic receptors. A primary focus of this report is the analysis of specific effects of these agents on the spontaneous and tone-evoked discharge and on different temporal components of the evoked discharge. Single neurons were recorded in the auditory cortex of chronically prepared, awake cats with multibarrel micropipette electrodes. The responses to acoustic stimuli were obtained before, during, and following continuous ejection of cholinergic agonist or antagonists by micropressure. The mean rate of discharge of the neurons was analyzed quantitatively for spontaneous discharge and for different peaks of the tone-evoked PSTH corresponding to tone "on," "through," and "off" responses. Acetylcholine (ACh) and acetyl-beta-methacholine (MCh) produced significant effects on spontaneous activity in 72% and 68% of neurons tested, respectively. Tone-evoked responses were effected in 92% and 82% of cells tested, respectively. The ability of these agonists to modify spontaneous or evoked activity was dose-dependent. Agonist effects on spontaneous and evoked activity were often different in the same cell; however, effects on spontaneous activity did predict effects on "through" responses. The most common effect of ACh or MCh on evoked activity was facilitation of the tone "on" response. For neurons with multicomponent discharge patterns in response to tones, the agonists had nonuniform effects on different response components. However, the effects of ACh on the "on" and "off" responses covaried. Hence cholinergic agonists produce heterogeneous, selective effects on different components of the responses of auditory cortical neurons rather than simple increases or decreases in discharge level. The effects of cholinergic agonists were modified in the presence of atropine. The effects of MCh were blocked by atropine in a higher proportion of cases than those of ACh.
本实验研究了胆碱能激动剂和拮抗剂对听觉皮层神经元自发放电和听觉诱发放电的影响，并检验了这些效应是否由毒蕈碱型胆碱能受体介导。本报告的一个主要重点是分析这些药物对自发放电和纯音诱发放电以及对诱发放电的不同时间成分的特定效应。使用多管微电极在长期制备的清醒猫的听觉皮层中记录单个神经元。通过微压连续喷射胆碱能激动剂或拮抗剂之前、期间和之后，获取对声刺激的反应。对神经元的平均放电率进行定量分析，以研究自发放电以及与纯音“开”、“持续”和“关”反应相对应的纯音诱发PSTH的不同峰值。乙酰胆碱（ACh）和乙酰-β-甲基胆碱（MCh）分别对72%和68%的受试神经元的自发放电产生显著影响。对92%和82%的受试细胞的纯音诱发反应产生影响。这些激动剂改变自发放电或诱发活动的能力呈剂量依赖性。在同一细胞中，激动剂对自发放电和诱发活动的影响通常不同；然而，对自发放电的影响确实能预测对“持续”反应的影响。ACh或MCh对诱发活动最常见的影响是促进纯音“开”反应。对于对纯音有多成分放电模式的神经元，激动剂对不同反应成分有不均匀的影响。然而，ACh对“开”和“关”反应的影响是协同变化的。因此，胆碱能激动剂对听觉皮层神经元反应不同成分产生异质性、选择性效应，而不是简单地增加或降低放电水平。在阿托品存在的情况下，胆碱能激动剂的效应会发生改变。与ACh相比，阿托品在更高比例的情况下阻断了MCh的效应。
