Takahashi Kuniyuki, Hishida Ryuichi, Kubota Yamato, Kudoh Masaharu, Takahashi Sugata, Shibuki Katsuei
Department of Neurophysiology, Brain Research Institute, Niigata University, Japan.
Eur J Neurosci. 2006 Mar;23(5):1365-76. doi: 10.1111/j.1460-9568.2006.04662.x.
Functional brain imaging using endogenous fluorescence of mitochondrial flavoprotein is useful for investigating mouse cortical activities via the intact skull, which is thin and sufficiently transparent in mice. We applied this method to investigate auditory cortical plasticity regulated by acoustic environments. Normal mice of the C57BL/6 strain, reared in various acoustic environments for at least 4 weeks after birth, were anaesthetized with urethane (1.7 g/kg, i.p.). Auditory cortical images of endogenous green fluorescence in blue light were recorded by a cooled CCD camera via the intact skull. Cortical responses elicited by tonal stimuli (5, 10 and 20 kHz) exhibited mirror-symmetrical tonotopic maps in the primary auditory cortex (AI) and anterior auditory field (AAF). Depression of auditory cortical responses regarding response duration was observed in sound-deprived mice compared with naïve mice reared in a normal acoustic environment. When mice were exposed to an environmental tonal stimulus at 10 kHz for more than 4 weeks after birth, the cortical responses were potentiated in a frequency-specific manner in respect to peak amplitude of the responses in AI, but not for the size of the responsive areas. Changes in AAF were less clear than those in AI. To determine the modified synapses by acoustic environments, neural responses in cortical slices were investigated with endogenous fluorescence imaging. The vertical thickness of responsive areas after supragranular electrical stimulation was significantly reduced in the slices obtained from sound-deprived mice. These results suggest that acoustic environments regulate the development of vertical intracortical circuits in the mouse auditory cortex.
利用线粒体黄素蛋白的内源性荧光进行功能性脑成像，对于通过完整颅骨研究小鼠皮层活动很有用，因为小鼠的颅骨薄且具有足够的透明度。我们应用此方法来研究由声学环境调节的听觉皮层可塑性。将出生后在各种声学环境中饲养至少4周的C57BL/6品系正常小鼠用乌拉坦（1.7 g/kg，腹腔注射）麻醉。通过冷却的电荷耦合器件相机经完整颅骨记录蓝光下内源性绿色荧光的听觉皮层图像。由音调刺激（5、10和20千赫）引发的皮层反应在初级听觉皮层（AI）和前听觉场（AAF）中呈现镜像对称的音调拓扑图。与在正常声学环境中饲养的未处理小鼠相比，在声音剥夺小鼠中观察到关于反应持续时间的听觉皮层反应减弱。当小鼠在出生后暴露于10千赫的环境音调刺激超过4周时，AI中反应的峰值幅度在频率特异性方面皮层反应增强，但反应区域的大小没有变化。AAF中的变化不如AI中的明显。为了确定由声学环境改变突触，用内源性荧光成像研究了皮层切片中的神经反应。在从声音剥夺小鼠获得的切片中，颗粒上电刺激后反应区域的垂直厚度显著减小。这些结果表明，声学环境调节小鼠听觉皮层中垂直皮质内回路的发育。
