GABA拮抗剂荷包牡丹碱对猫外膝体神经元方位调谐特性的影响

EFFECTS OF GABA ANTAGONIST BICUCULLINE ON THE ORIENTATION TUNING CHARACTER OF RELAY CELLS IN DORSAL LATERAL GENICULATE ATE NUCLEUS(dLGN)

在十二只成年猫上用多管玻璃微电极记录了外膝体神经元对不同空间频率和不同方位的移动正弦光栅刺激的反应，共详细测定并对比研究了３８个方位敏感性细胞在微电泳荷包牡丹碱前后的方位调谐特性。在最优空间频率附近的较低空间频率下，微电泳荷包牡丹碱后，外膝体细胞的方位敏感性强度（Ｂｉａｓ）降低，而在截止频率附近的较高空间频率下，微电泳前后外膝细胞的方位敏感性强度（Ｂｉａｓ）从总体上看没有显著变化。结果表明，以空间频率为截止频率附近的移动正弦光栅作为刺激，外膝体细胞的方位敏感性可能主要是由视网膜神经节细胞的兴奋输入所形成，而非外膝体内抑制机制所致。

Responses to sinusoidal drifting gratings of different spatial frequencies (SF) anddifferent orientations were recorded form cat's orientation sensitive neurons in lamina A and Alof the dorsal latelal geniculate nucleus (dLGN) with multimicrocapillary electtrodes andmicroiontophoresis technique. We quantitahvely measured and compared orientation sensitive biases (OB>0.1) of those Cells (38 total) before and after microiontophoresis of bicuculline, aGABA antagonist.The orientation sensitive biases at low SF near the Cell's preferred SF reduced significantly,but no remarkable change for dLGN neurons near their cut-off SF Wasdetected afterbicuculline applied.The results showed that the orientation sensitivity of dLGN neurons,measured tosinusoidal drifting gratings just near the Cell's cut-off spatial freqence,might be contributed bythe excitatory inputs of retina ganglion cells,but not by the inhibitory mechanism within thedLGN.keywods: Orientation tuning character Bicuculline Receptive field Dorsal lateral geniculate nuclesus Cat