Evidence for a pathway that facilitates nitric oxide diffusion in the brain |
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Authors: | Santos Ricardo M Lourenço Cátia F Gerhardt Greg A Cadenas Enrique Laranjinha João Barbosa Rui M |
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Affiliation: | a Center for Neuroscience and Cell Biology, University of Coimbra, Largo Marquês de Pombal, Coimbra 3004-517, Portugal b Department of Anatomy and Neurobiology, Center for Microelectrode Technology, University of Kentucky, Lexington, KY 40536-0098, USA c Pharmacology and Pharmaceutical Sciences Faculty, University of Southern California, Los Angeles, CA 90089-9121, USA d Faculty of Pharmacy, University of Coimbra, Azinhaga de Santa Comba, Coimbra 3000-548, Portugal |
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Abstract: | Nitric oxide (NO) is a diffusible messenger that conveys information based on its concentration dynamics, which is dictated by the interplay between its synthesis, inactivation and diffusion. Here, we characterized NO diffusion in the rat brain in vivo. By direct sub-second measurement of NO, we determined the diffusion coefficient of NO in the rat brain cortex. The value of 2.2 × 10−5 cm2/s obtained in vivo was only 14% lower than that obtained in agarose gel (used to evaluate NO free diffusion). These results reinforce the view of NO as a fast diffusing messenger but, noticeably, the data indicates that neither NO diffusion through the brain extracellular space nor homogeneous diffusion in the tissue through brain cells can account for the similarity between NO free diffusion coefficient and that obtained in the brain. Overall, the results support that NO diffusion in brain tissue is heterogeneous, pointing to the existence of a pathway that facilitates NO diffusion, such as cell membranes and other hydrophobic structures. |
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Keywords: | PBS, phosphate buffered saline o-PD, ortho-phenylenediamine BSA, bovine serum albumin |
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