Fig. 3

Quantification of microscopic axial section tracer fluorescence (integrated density) per spinal level after grey and white matter injections. Each spinal cord level (“Level”) is expressed as the number of levels rostral (positive integers) or caudal (negative integers) to injection site. All error bars are expressed as ± SEM. a After grey matter injections at 20 min (n = 5) there was no statistical difference between grey and white matter fluorescence. b This was also observed in grey matter injections after 60 min (n = 5). However, after white matter injections at c 20 min (n = 5) and at d 60 min (n = 5), there was significantly greater tracer fluorescence in the white matter compared to the grey matter (p = 0.0094 and 0.0041 for 20 and 60 min respectively). On post hoc analysis, a statistically significant difference was observed at one level caudal to the injection site (***p < 0.0001) at 20 min (c), and one level rostral and caudal at 60 min (d) (**p = 0.0017, ****p < 0.0001)