Beware, surgery screws with your mouse's mind!

In 2002 two groups published apparently contradictory results in the same issue of Nature. One group, lead by Wen-Biao Gan, said spines heads were essentially stable in the cortex when followed for long periods using in vivo 2P imaging. Svoboda's group had an article that said "the opposite". Each group used H-line mice, the difference was that Gan imaged through a thinned skull, whereas Svoboda through an implanted window.

Gan and colleagues have now attempted to solve the puzzling difference between these 2 landmark papers. They have found that even a carefully installed craniotomy can change profoundly the structure of glia close to the volume of surgery (see image above, Fig 3S from their paper- doi:10.1038/nn1883). (a) is an image of GFP-micro glia taken through the skull, and (b) is from a mouse with a 'hole in its head'. The structure of the micro glia is quite different. In experiments with GFAP-GFP astrocytes they see a significant increase in GFAP, implying "reactive astrocytes" are produced by surgery. One can easily imagine that glia restructuring could enhance spine-head loss in the cortex. They conclude: "Our findings suggest that the choice of cranial window type for in vivo imaging is the major factor contributing to previous discrepancies observed in spine dynamics under both normal and sensory deprivation conditions."

"Choice of cranial window type for in vivo imaging affects dendritic spine turnover in the cortex." Nature Neuroscience (2007) doi:10.1038/nn1883.

Grutzendler, J., Kasthuri, N. & Gan, W.B. Nature 420, 812–816 (2002).

Trachtenberg, J.T. et al. Nature 420, 788–794 (2002).