Chen Q C, Jen P H
Division of Biological Sciences, University of Missouri-Columbia, Columbia, MO 65211, USA.
Hear Res. 2000 Dec;150(1-2):161-74. doi: 10.1016/s0378-5955(00)00197-0.
This study examined the effect of bicuculline application on the auditory response properties in the auditory cortex of the big brown bat, Eptesicus fuscus. All auditory cortical neurons studied discharged either 1-2 or 3-7 impulses to 4 ms sound stimuli. Cortical neurons with high best frequencies tended to have high minimum thresholds. Bicuculline application increased the number of impulses and shortened the response latencies of all cortical neurons as well as changing the discharge patterns of half of the cortical neurons studied. Bicuculline application raised the rate-intensity functions but lowered the latency-intensity functions to varying degrees. Threshold-frequency tuning curves (FTCs) were either V-shaped, upper threshold or double-peaked. Threshold-FTCs and impulse-FTCs were mirror-images of each other. Bicuculline application expanded and raised the impulse-FTCs but lowered the threshold-FTCs, resulting in significantly decreased Q(n) values. Threshold-FTCs of cortical neurons determined within an orthogonally inserted electrode were very similar and expanded FTCs during bicuculline application were also very similar. Possible mechanisms for the contribution of GABAergic inhibition to shaping these response properties of cortical neurons are discussed.
本研究考察了荷包牡丹碱的应用对大棕蝠（棕蝠）听觉皮层听觉反应特性的影响。所有被研究的听觉皮层神经元对4毫秒的声音刺激发放1 - 2个或3 - 7个冲动。具有高最佳频率的皮层神经元往往具有较高的最小阈值。应用荷包牡丹碱增加了所有皮层神经元的冲动数量，缩短了反应潜伏期，并改变了所研究的一半皮层神经元的放电模式。应用荷包牡丹碱不同程度地提高了发放率 - 强度函数，但降低了潜伏期 - 强度函数。阈值 - 频率调谐曲线（FTCs）呈V形、上阈值或双峰形。阈值 - FTCs和冲动 - FTCs互为镜像。应用荷包牡丹碱使冲动 - FTCs扩展并升高，但降低了阈值 - FTCs，导致Q(n)值显著降低。在正交插入电极内确定的皮层神经元的阈值 - FTCs非常相似，应用荷包牡丹碱期间扩展的FTCs也非常相似。文中讨论了γ - 氨基丁酸能抑制对塑造皮层神经元这些反应特性的贡献的可能机制。
