Pain Mechanisms and Sensory NeuroscienceResearch PaperIntegration of CO2 and odorant signals in the mouse olfactory bulb
Section snippets
Animals and anesthesia
Animal care and use conformed to the institutional guidelines of the National Institute of Biological Science and were in accordance with the policies of the US National Institute of Health. Male C57/BL6 mice (8–12 weeks) were obtained from VitalRiver Laboratory Animal Inc. (Beijing, China). For anesthesia, mice were injected with atropine (50 mg/kg, i.p., Sigma-Aldrich) and then urethane (1.64 g/kg, i.p., Sinopharm, Shanghai, China).
Electrophysiology
After anesthesia, a mouse was placed on a custom-made
CO2-activating neurons in the olfactory bulb respond selectively to odorants
To test whether bulbar neurons can respond to both CO2 and odorants, we first searched for CO2-activating neurons by targeting recording electrodes into the caudal end of the olfactory bulb where the necklace glomeruli are located (Hu et al., 2007, Walz et al., 2007). Putative M/T cells were identified based on the fact that these cells were recorded from a thin layer with clear spontaneous activity coupled to respiratory rhythms. CO2-responsiveness was tested by puffing 2-s CO2 pulses
Discussion
In mice, CO2 activates a specialized subset of OSNs that project to the necklace glomeruli in the caudal olfactory bulb (Hu et al., 2007, Sun et al., 2009). Our recordings from this study revealed that CO2-activating bulbar neurons also respond to odorants, suggesting strong interaction between CO2 and odorant signals in the olfactory bulb. Here we will discuss the implications of our data on the function of CO2 as a behavioral cue as well as the possible circuitry mechanisms underlying the
Acknowledgments
We thank A.L. Person for critical reading of the manuscript. This study was supported by a Project 973 grant (2010CB833902) and a Project 863 grant (2008AA022312) from China Ministry of Science and Technology to ML.
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