Silbering Ana F, Galizia C Giovanni
Institute of Neurobiology, Free University of Berlin, 14195 Berlin, Germany.
J Neurosci. 2007 Oct 31;27(44):11966-77. doi: 10.1523/JNEUROSCI.3099-07.2007.
To understand how odor information is represented and processed in the antennal lobe (AL) of Drosophila melanogaster, we have optically recorded glomerular calcium responses to single odors and odor mixtures from olfactory sensory neurons (OSNs) and projection neurons (PNs). Odor mixtures offer a good tool to analyze odor processing because experimental results can be tested against clear predictions. At the level of the OSNs, the representation of odor mixtures could be predicted from the response patterns of the components in most cases. PN responses to mixtures, however, provide evidences of interglomerular inhibition. Application of picrotoxin (PTX), an antagonist of GABA(A)-like receptors, enhanced odor responses, modified their temporal course, and eliminated mixture suppression at the PN level. Our results can be best explained by postulating the existence of at least two local networks in the fly AL: a glomerulus specific network, which includes excitatory and inhibitory connections and a PTX sensitive inhibitory global network that acts on all glomeruli with proportional strength to the global AL input.
为了了解黑腹果蝇触角叶（AL）中气味信息是如何被表征和处理的，我们通过光学记录了嗅觉感觉神经元（OSN）和投射神经元（PN）对单一气味和气味混合物的肾小球钙反应。气味混合物为分析气味处理提供了一个很好的工具，因为实验结果可以根据明确的预测进行检验。在OSN水平上，在大多数情况下，可以根据各成分的反应模式预测气味混合物的表征。然而，PN对混合物的反应提供了肾小球间抑制的证据。应用苦味毒素（PTX），一种γ-氨基丁酸A型（GABA(A)）样受体拮抗剂，增强了气味反应，改变了它们的时间进程，并消除了PN水平上的混合物抑制。我们的结果可以通过假设果蝇AL中至少存在两个局部网络来最好地解释：一个肾小球特异性网络，它包括兴奋性和抑制性连接；以及一个PTX敏感的抑制性全局网络，它以与全局AL输入成比例的强度作用于所有肾小球。
