Buerk D G, Riva C E, Cranstoun S D
Department of Ophthalmology, Scheie Eye Institute, Philadelphia, PA, USA.
Invest Ophthalmol Vis Sci. 1995 Oct;36(11):2216-27.
The purpose of this study was to investigate whether blood flow in the cat optic nerve head (ONH) is related to increased neuronal activity elicited by diffuse luminance flickering light stimulation.
ONH blood flow was measured by laser Doppler flowmetry in anesthetized cats during 1 to 3 minutes of flickering light stimulation at controlled luminance and frequency (n = 227 measurements in 18 cats) using either a conventional visual stimulator (repetitive short flashes) or a sinusoidally varying light stimulator. Potassium ion concentration ([K+]) changes in the vitreous humor immediately in front of the optic disk were measured with neutral carrier K+ ionophore liquid membrane microelectrodes. Effects of varying flicker frequency (2 to 80 Hz) at constant luminance were quantified. Effects of luminance were quantified by varying the modulation depth of the stimulus at constant frequency.
Both ONH blood flow and [K+] increased during flicker stimulus with an average slope of 0.305% +/- 0.064% (SE)/microM [K+] (257 measurements in 18 cats). The peak ONH blood flow increase was 59% +/- 11% above baseline at 33.3 +/- 3.1 Hz. The peak [K+] increase was 188 +/- 42 microM above baseline at 38.3 +/- 3.3 Hz. Both ONH blood flow and [K+] changes had similar bandpass characteristics with frequency, first increasing, then dropping off at higher frequencies (122 measurements in 10 cats). Both frequency responses were described by power law functions (y = af"). Luminance responses for both ONH blood flow and [K+] changes could be fit by a modified Hill model and were 50% of maximum at light modulation depths of 21.2% +/- 4.6% and 22.5% +/- 3.7%, respectively (53 measurements in 5 cats).
Increases in ONH blood flow were correlated with changes in [K+]. Both responses were remarkably similar, with no significant differences in the frequency for peak responses in ONH blood flow or [K+], in low- and high-frequency power law exponents of the two responses, or in the 50% response to light modulation. The results are consistent with close coupling of neuronal activity and ONH blood flow.
本研究旨在探究猫视神经乳头（ONH）的血流是否与由漫射亮度闪烁光刺激引起的神经元活动增加有关。
在使用传统视觉刺激器（重复短闪光）或正弦变化光刺激器对麻醉猫进行1至3分钟的闪烁光刺激期间，通过激光多普勒血流仪测量ONH血流，刺激的亮度和频率可控（18只猫进行了227次测量）。使用中性载体钾离子载体液膜微电极测量紧邻视盘前方玻璃体液中钾离子浓度（[K⁺]）的变化。对在恒定亮度下改变闪烁频率（2至80Hz）的影响进行了量化。通过在恒定频率下改变刺激的调制深度来量化亮度的影响。
在闪烁刺激期间，ONH血流和[K⁺]均增加，平均斜率为0.305%±0.064%（标准误）/微摩尔[K⁺]（18只猫进行了257次测量）。在33.3±3.1Hz时，ONH血流增加的峰值比基线高59%±11%。在38.3±3.3Hz时，[K⁺]增加的峰值比基线高188±42微摩尔。ONH血流和[K⁺]的变化在频率方面具有相似的带通特性，先是增加，然后在较高频率时下降（10只猫进行了122次测量）。两种频率响应均由幂律函数（y = afⁿ）描述。ONH血流和[K⁺]变化的亮度响应都可以用修正的希尔模型拟合，在光调制深度分别为21.2%±4.6%和22.5%±3.7%时达到最大值的50%（5只猫进行了53次测量）。
ONH血流的增加与[K⁺]的变化相关。两种反应非常相似，在ONH血流或[K⁺]的峰值反应频率、两种反应的低频和高频幂律指数以及对光调制的50%反应方面均无显著差异。结果与神经元活动和ONH血流的紧密耦合一致。
