Groner M, Fisch H U, Walder F, Groner R, Hofer D, Koelbing U, Duss I, Bianchi R, Bircher B
Department of Psychology, University of Berne, Switzerland.
Psychopharmacology (Berl). 1992;109(1-2):68-76. doi: 10.1007/BF02245482.
Psychophysical experiments in humans have revealed similar characteristics of visual receptive fields as were found in cats and monkeys from retinal ganglion cell recordings. In addition, in some retinal ganglion cells of cats the GABA antagonist bicuculline decreases the activity of the inhibitory surround. These findings led to two predicitions: 1) benzodiazepines will selectively increase the inhibitory surround of human visual receptive fields, 2) after dark adaptation, no free GABA will be available in the synapses and benzodiazepines will have no effect on the visual system. Characteristics of human receptive fields were determined by subthreshold summation: the contrast threshold of a vertical line was measured dependent on the distance of two parallel flanking lines whose contrast was below threshold. Both hypotheses were confirmed: the threshold in the inhibitory region of receptive fields was specifically increased in a dose-dependent manner by midazolam PO (7.5 mg: P < 0.05; 15 mg: P < 0.01). In dark-adapted subjects no effect of midazolam was found. Control experiments with atropine (1 mg IV), sulpiride (100 mg IM), and levodopa (100 mg PO) showed no specific effect. The visual system may be a model to bridge the gap between animal and human psychopharmacology.
在人类身上进行的心理物理学实验揭示了视觉感受野的类似特征，这些特征与通过记录猫和猴子视网膜神经节细胞所发现的特征相同。此外，在猫的一些视网膜神经节细胞中，GABA拮抗剂荷包牡丹碱会降低抑制性周边的活性。这些发现产生了两个预测：1）苯二氮䓬类药物将选择性地增强人类视觉感受野的抑制性周边；2）在暗适应后，突触中不会有游离的GABA，且苯二氮䓬类药物对视觉系统将没有影响。人类感受野的特征通过阈下总和来确定：测量垂直线的对比度阈值，该阈值取决于两条平行侧翼线的距离，这两条侧翼线的对比度低于阈值。这两个假设均得到证实：口服咪达唑仑（7.5毫克：P<0.05；15毫克：P<0.01）以剂量依赖的方式特异性地提高了感受野抑制区域的阈值。在暗适应的受试者中未发现咪达唑仑有作用。用阿托品（静脉注射1毫克）、舒必利（肌肉注射100毫克）和左旋多巴（口服100毫克）进行的对照实验未显示出特异性作用。视觉系统可能是一个用以弥合动物和人类精神药理学之间差距的模型。
