嗅觉感知中温度恒定性的神经机制

Temperature affects most biological processes. When temperature changes, animals need to measure such changes precisely with thermosensors and keep perception constant for other senses. The neural mechanisms underlying perception constancy at different temperatures remain unknown. Our published results demonstrate that temperature can change the firing of spontaneous action potentials in olfactory sensory neurons (OSNs), whose inhibition by odors drives olfaction perception. However, our preliminary results show that olfaction perception in Drosophila do not change with temperature. In this proposal, we will investigate the neural mechanisms underlying olfaction constancy at different temperatures. Our specific aims are: 1) whether the increase of spontaneous firing at higher temperatures boosts odor-induced inhibitory responses but reduces signal-to-noise ratio of odor-induced excitatory responses, and whether the decrease of spontaneous firing at lower temperatures reduces odor-induced inhibitory responses but increases signal-to-noise ratio of odor-induced excitatory responses; 2) whether opposite temperature effects on inhibitory and excitatory responses compensate each other to maintain the constancy of olfaction perception at different temperatures. The insights gained from this project will not only improve our understanding of temperature effects on olfaction but also facilitate the understanding of temperature effects on other neuronal processes in general.

温度影响几乎所有生命过程。温度变化时，人和动物用温度感受器精确感受温度的变化，同时还需维持其它感知的恒定性。然而，感知的温度恒定性的神经机制还完全不清楚。我们已有的研究表明，参与嗅觉感知的嗅感觉神经元自发动作电位的发放可随温度变化而改变。但我们的初步结果表明，果蝇对气味的感知在一定温度范围内可维持稳定不变。在该申请项目中，我们研究嗅觉感知中温度恒定性的神经机制。我们研究：1）在温度较高时，嗅感觉神经元自发动作电位发放的增加是否增大抑制性气味反应，但降低兴奋性气味反应的信噪比；在温度较低时，自发动作电位的减少是否减小抑制性气味反应，但提高兴奋性气味反应的信噪比；2）温度对抑制性和兴奋性反应的相反调节是否使气味感知相互补偿而维持稳定不变。该项目的结果不仅可加深我们对温度变化影响嗅觉感知和行为的理解，也将为理解温度变化对其它神经系统的影响提供理论指导。

温度影响生物化学反应，从而影响每一个生命过程。虽然一些单细胞功能可以通过蛋白信号转导的平衡来承受温度变化，但目前尚不清楚这种温度调节的弹性是否可在多细胞生物中实现。在这里，我们展示了黑腹果蝇在温度变化下对各种气味保持稳定的行为偏好。这种温度恒定性在只表达一种功能性气味受体(Or)的转基因果蝇中无法维持，但在表达两种Or的果蝇中可以重建，它们对极性相反的同一气味作出反应，并驱动相同的行为偏好。在机制上，温度改变Or的基础的自发活动，从相反的方向调节兴奋性和抑制性气味信号。这些相反的调节在驱动相同气味偏好时相互补偿。我们的研究结果定义了温度补偿的最小单位，以气味双向编码为基础，为适应温度变化的生理功能提供了新的见解。