Juliano S L, Whitsel B L, Tommerdahl M, Cheema S S
Department of Anatomy, USUHS, Bethesda, Maryland 20814.
J Neurosci. 1989 Jan;9(1):1-12. doi: 10.1523/JNEUROSCI.09-01-00001.1989.
Despite repeated experimental demonstration that somatic stimulation leads to an intermittent, "column-like" pattern of 2-deoxyglucose (2DG) label in the somatosensory cortex, the functional significance of this pattern remains uncertain. A number of recent studies have suggested that the putative inhibitory neurotransmitter GABA may play an influential role in the cortical processing of sensory information. To test the possibility that GABA-mediated inhibitory processes might participate in the formation of the 2DG patches, the 2DG pattern obtained under "normal" experimental conditions was compared with the pattern observed when cortical inhibition was modified by topical application of the GABA antagonist, bicuculline methiodide (BIC). Under "normal" experimental conditions, we found that somatic stimulation led to an intermittent, patch like distribution of 2DG uptake in cat somatosensory cortex, which exhibited consistent features in animals studied using the same stimulus and experimental condition. Reconstructions of the stimulus-evoked activity patterns revealed that the label was confined to territories known to receive input from the stimulated body region and was organized into elongated strips. Topical application of BIC to the somatosensory cortex dramatically altered the dimension of the metabolic patches, which were often embedded in a field of elevated 2DG uptake. In BIC-treated hemispheres the average width of 2DG patches was 1266 microns, whereas the average width of patches in the opposite untreated hemisphere (elicited by identical stimuli) was 713 microns. Unfolded maps of the labeling pattern revealed that in the BIC-treated hemispheres adjacent "strips" of 2DG label tended to fuse, leading to a less intermittent distribution than that observed in the untreated hemispheres. An important role for GABA in the formation of the normal cortical response to somatic stimulation is suggested.
尽管反复的实验证明，躯体刺激会在体感皮层导致2-脱氧葡萄糖（2DG）标记呈现间歇性的“柱状”模式，但这种模式的功能意义仍不明确。最近的一些研究表明，假定的抑制性神经递质γ-氨基丁酸（GABA）可能在感觉信息的皮层处理中发挥重要作用。为了检验GABA介导的抑制过程可能参与2DG斑块形成的可能性，将“正常”实验条件下获得的2DG模式与通过局部应用GABA拮抗剂甲磺酸荷包牡丹碱（BIC）改变皮层抑制时观察到的模式进行了比较。在“正常”实验条件下，我们发现躯体刺激导致猫体感皮层中2DG摄取呈间歇性的斑块状分布，在使用相同刺激和实验条件进行研究的动物中表现出一致的特征。对刺激诱发活动模式的重建显示，标记局限于已知接受来自受刺激身体区域输入的区域，并组织成细长条带。将BIC局部应用于体感皮层显著改变了代谢斑块的尺寸，这些斑块通常嵌入2DG摄取升高的区域。在经BIC处理的半球中，2DG斑块的平均宽度为1266微米，而在未处理的对侧半球（由相同刺激诱发）中斑块的平均宽度为713微米。标记模式的展开图显示，在经BIC处理的半球中，相邻的2DG标记“条带”倾向于融合，导致分布的间歇性比未处理半球中观察到的要小。这表明GABA在对躯体刺激的正常皮层反应形成中起重要作用。
