Heinbockel T, Christensen T A, Hildebrand J G
Department of Physiology and Program in Neuroscience, University of Maryland School of Medicine, 655 W. Baltimore Street, Baltimore, MD 21201-1509, USA.
J Comp Physiol A Neuroethol Sens Neural Behav Physiol. 2004 Dec;190(12):1023-37. doi: 10.1007/s00359-004-0559-7. Epub 2004 Sep 17.
An outstanding challenge in olfactory neurobiology is to explain how glomerular networks encode information about stimulus mixtures, which are typical of natural olfactory stimuli. In the moth Manduca sexta, a species-specific blend of two sex-pheromone components is required for reproductive signaling. Each component stimulates a different population of olfactory receptor cells that in turn target two identified glomeruli in the macroglomerular complex of the male's antennal lobe. Using intracellular recording and staining, we examined how responses of projection neurons innervating these glomeruli are modulated by changes in the level and ratio of the two essential components in stimulus blends. Compared to projection neurons specific for one component, projection neurons that integrated information about the blend (received excitatory input from one component and inhibitory input from the other) showed enhanced ability to track a train of stimulus pulses. The precision of stimulus-pulse tracking was furthermore optimized at a synthetic blend ratio that mimics the physiological response to an extract of the female's pheromone gland. Optimal responsiveness of a projection neuron to repetitive stimulus pulses therefore appears to depend not only on stimulus intensity but also on the relative strength of the two opposing synaptic inputs that are integrated by macroglomerular complex projection neurons.
嗅觉神经生物学面临的一个突出挑战是解释肾小球网络如何编码有关刺激混合物的信息，而刺激混合物是自然嗅觉刺激的典型特征。在烟草天蛾中，两种性信息素成分的物种特异性混合物是生殖信号传递所必需的。每种成分刺激不同群体的嗅觉受体细胞，这些细胞进而靶向雄性触角叶大肾小球复合体中的两个已确定的肾小球。我们使用细胞内记录和染色技术，研究了支配这些肾小球的投射神经元的反应是如何被刺激混合物中两种必需成分的水平和比例变化所调节的。与对一种成分具有特异性的投射神经元相比，整合了混合物信息（从一种成分接收兴奋性输入，从另一种成分接收抑制性输入）的投射神经元表现出更强的跟踪一系列刺激脉冲的能力。此外，在模拟对雌性信息素腺提取物的生理反应的合成混合比例下，刺激脉冲跟踪的精度得到了优化。因此，可以看出，投射神经元对重复刺激脉冲的最佳反应性不仅取决于刺激强度，还取决于由大肾小球复合体投射神经元整合的两种相反突触输入的相对强度。
