Original ContributionNeurovascular coupling in hippocampus is mediated via diffusion by neuronal-derived nitric oxide
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Section snippets
Array for NO and CBF measurements
The NO sensors were fabricated as previously described [24]. Briefly, a single carbon fiber (30 µm Ø; Textron, Lowell, MA, USA) was encased in a glass capillary and pulled in a vertical puller. The protruding carbon fiber was cut to a tip length of 200±50 µm. The electrical contact between the carbon fiber and a copper wire was achieved by using conductive silver paint (RS, Northants, UK). To improve their analytical properties for in vivo measurements of NO, the sensors were coated with Nafion
Nitric oxide and cerebral blood flow changes: coupling in space, time, and amplitude
We have previously reported that a controlled and localized glutamate stimulus in the rat hippocampus promotes an instantaneous and transient elevation of NO concentration levels through the activation of ionotropic glutamate receptors [23]. By upgrading such experimental strategy, simultaneously measuring local CBF, we observed that a transient NO increase induced by glutamate ejection (0.5 nmol, 25 nl, 1 s), was followed, seconds later, by a transient change in CBF (Fig. 1). NO production was
Discussion
The mechanisms that regulate the synergy between cerebral microcirculation and local neuronal activity have been debated over a century without clear conclusions, in part because of the severe experimental limitations to measure the process in real time in the natural working environment. The identification of NO as a diffusible vasodilator produced at active neurons, via ionotropic glutamate receptor-dependent pathways, led to the hypothesis that it could be the mediator coupling the brain
Acknowledgements
This work was supported by FCT grant (Portugal) PTDC/SAU-NEU/108992/2008.
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