Effect of basal forebrain stimulation on extracellular acetylcholine release and blood flow in the olfactory bulb
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The olfactory bulb receives cholinergic basal forebrain input, as does the neocortex; however, the in vivo physiological functions regarding the release of extracellular acetylcholine and regulation of regional blood flow in the olfactory bulb are unclear. We used in vivo microdialysis to measure the extracellular acetylcholine levels in the olfactory bulb of urethane-anesthetized rats. Focal chemical stimulation by microinjection of l-glutamate into the horizontal limb of the diagonal band of Broca (HDB) in the basal forebrain, which is the main source of cholinergic input to the olfactory bulb, increased extracellular acetylcholine release in the ipsilateral olfactory bulb. When the regional cerebral blood flow was measured using laser speckle contrast imaging, the focal chemical stimulation of the HDB did not significantly alter the blood flow in the olfactory bulb, while increases were observed in the neocortex. Our results suggest a functional difference between the olfactory bulb and neocortex regarding cerebral blood flow regulation through the release of acetylcholine by cholinergic basal forebrain input.
KeywordsCholinergic system Horizontal limb of the diagonal band of Broca Laser speckle contrast imaging Microdialysis Rat
This work was supported by JSPS KAKENHI (Grant Number JP15K08225 to S.U.) and by the Smoking Research Foundation.
Both authors contributed to the conception and design of the research, performed experiments and analyzed data, and interpreted the results of the experiments. S.U. drafted the manuscript; both authors edited and revised the manuscript, and approved the final manuscript.
Compliance with ethical standards
Conflict of interest
The authors have no conflicts of interest to declare.
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