| First Author | Yao X | Year | 2008 |
| Journal | J Neurosci | Volume | 28 |
| Issue | 21 | Pages | 5460-4 |
| PubMed ID | 18495879 | Mgi Jnum | J:136365 |
| Mgi Id | MGI:3796034 | Doi | 10.1523/JNEUROSCI.0257-08.2008 |
| Citation | Yao X, et al. (2008) Aquaporin-4-deficient mice have increased extracellular space without tortuosity change. J Neurosci 28(21):5460-4 |
| abstractText | Aquaporin-4 (AQP4) is the major water channel expressed at fluid-tissue barriers throughout the brain and plays a crucial role in cerebral water balance. To assess whether these channels influence brain extracellular space (ECS) under resting physiological conditions, we used the established real-time iontophoresis method with tetramethylammonium (TMA(+)) to measure three diffusion parameters: ECS volume fraction (alpha), tortuosity (lambda), and TMA(+) loss (k'). In vivo measurements were performed in the somatosensory cortex of AQP4-deficient (AQP4(-/-)) mice and wild-type controls with matched age. Mice lacking AQP4 showed a 28% increase in alpha (0.23 +/- 0.007 vs 0.18 +/- 0.003) with no differences in lambda (1.62 +/- 0.04 vs 1.61 +/- 0.02) and k' (0.0045 +/- 0.0001 vs 0.0031 +/- 0.0009 s(-1)). Additional recordings in brain slices showed similarly elevated alpha in AQP4(-/-) mice, and no differences in lambda and k' between the two genotypes. This is the first direct comparison of ECS properties in adult mice lacking AQP4 water channels with wild-type animals and demonstrates a significant enlargement of the volume fraction but no difference in hindrance to TMA(+) diffusion, expressed as tortuosity. These findings provide direct evidence for involvement of AQP4 in modulation of the ECS volume fraction and provide a basis for future modeling of water and ion transport in the CNS. |
