Ho Sabrina L, Johnson Brett A, Chen Andrew L, Leon Michael
Department of Neurobiology and Behavior, University of California, Irvine, California 92697-4550, USA.
J Comp Neurol. 2006 Dec 1;499(4):519-32. doi: 10.1002/cne.21139.
In an effort to understand mammalian olfactory processing, we have been describing the responses to systematically different odorants in the glomerular layer of the main olfactory bulb of rats. Previously, we demonstrated chemotopically organized and distinct olfactory responses to a homologous series of straight-chained alkanes that consisted of purely hydrocarbon structures, indicating that hydrocarbon chains could serve as molecular features in the combinatorial coding of odorant information. To better understand the processing of hydrocarbon odorants, we now have examined responses to other types of chemical changes in these kinds of molecules, namely, branching and carbon-carbon bond saturation. To this end, we used the [14C]2-deoxyglucose method to determine glomerular responses to a group of eight-carbon branched alkane isomers, unsaturated octenes (double-bonded), and octynes (triple-bonded). In contrast to the differential responses we observed previously for straight-chained alkanes of differing carbon number, the rat olfactory system was not particularly sensitive to these variations in branching and bond saturation. This result was unexpected, given the distinct molecular conformations and property profiles of the odorants. The similarity in activity patterns was paralleled by a similarity in spontaneous perceptual responses measured using a habituation assay. These results demonstrate again the functional relationship between bulbar activity patterns and odor perception. The results further suggest that the olfactory system does not respond equally to all aspects of odorant chemistry, functioning as a specific, rather than a general, chemical analysis system.
为了理解哺乳动物的嗅觉处理过程，我们一直在描述大鼠主嗅球肾小球层对系统不同气味剂的反应。此前，我们证明了对一系列由纯烃结构组成的直链烷烃的化学拓扑组织和独特的嗅觉反应，这表明烃链可以作为气味剂信息组合编码中的分子特征。为了更好地理解烃类气味剂的处理过程，我们现在研究了这类分子中其他类型化学变化的反应，即支化和碳 - 碳键饱和度。为此，我们使用[14C]2 - 脱氧葡萄糖方法来确定肾小球对一组八碳支链烷烃异构体、不饱和辛烯（双键）和辛炔（三键）的反应。与我们之前观察到的不同碳原子数直链烷烃的差异反应相反，大鼠嗅觉系统对这些支化和键饱和度的变化并不特别敏感。考虑到气味剂不同的分子构象和性质特征，这一结果出乎意料。使用习惯化试验测量的自发感知反应的相似性与活动模式的相似性相平行。这些结果再次证明了嗅球活动模式与气味感知之间的功能关系。结果进一步表明，嗅觉系统对气味剂化学的所有方面并非同等反应，而是作为一个特定的而非通用的化学分析系统发挥作用。
