McKenna T M, Ashe J H, Weinberger N M
Center for the Neurobiology of Learning and Memory, University of California, Irvine 92717.
Synapse. 1989;4(1):30-43. doi: 10.1002/syn.890040105.
Previously we reported that acetylcholine (ACh) and acetyl-beta-methacholine (MCh) modify responses of neurons in auditory cortex to individual frequencies. The purpose of this study was to determine whether muscarinic agonists produce frequency-specific alterations or general changes in cellular responses. Frequency-specific modifications would be evident in alterations of frequency receptive fields (FRF) that differed across frequencies while general effects would be seen as changes that were more or less the same over frequencies. Responses of single neurons to designated sets of tones were recorded in the auditory cortex of chronically prepared awake cats before, during, and following ejection of ACh or MCh by iontophoresis or micropressure using multibarrel micropipettes. Frequency receptive fields were determined by presenting isointensity tones across a range of frequencies including the cell's best frequency (BF) to tone onset. FRF for "off" and "sustained (through)" responses were also determined quantitatively. The effects of ACh and MCh were predominantly frequency-specific (77%, 39/51 cells); general changes (19%, 10/51) and no effects (4%, 2/51) were less likely. Frequency-specific effects involved both facilitation and reduction of the same response component to different frequencies within the same neuron. For responses to tone onset (but not "through" and "off" responses), agonists were more likely to produce a decrease at the BF while simultaneously increasing responses to other frequencies. Agonists could increase or decrease frequency selectivity. Effects of agonists could be blocked by atropine, suggesting involvement of muscarinic receptors.
此前我们报道过，乙酰胆碱（ACh）和乙酰-β-甲基胆碱（MCh）可改变听觉皮层神经元对各个频率的反应。本研究的目的是确定毒蕈碱激动剂是产生频率特异性改变还是引起细胞反应的一般性变化。频率特异性改变在不同频率的频率感受野（FRF）变化中很明显，而一般性效应则表现为在各个频率上或多或少相同的变化。使用多管微电极通过离子电泳或微压法在慢性制备的清醒猫的听觉皮层中，在注入ACh或MCh之前、期间和之后，记录单个神经元对指定音调组的反应。通过呈现一系列频率（包括细胞的最佳频率（BF））的等强度音调来确定频率感受野。还定量确定了“关闭”和“持续（贯穿）”反应的FRF。ACh和MCh的作用主要是频率特异性的（77%，39/51个细胞）；一般性变化（19%，10/51）和无作用（4%，2/51）的情况较少见。频率特异性效应涉及同一神经元内对不同频率的相同反应成分的促进和抑制。对于对音调起始的反应（但不是“贯穿”和“关闭”反应），激动剂更有可能在BF处产生降低，同时增加对其他频率的反应。激动剂可以增加或降低频率选择性。激动剂的作用可被阿托品阻断，提示毒蕈碱受体参与其中。
