Melatonin improves the ultrastructural myelin aspect in GR pups.

(A–F) Cingulate white matter ultrastructural aspect observed using electron microscopy. PBS-treated GR pups (B, C) exhibited swollen axons (marked with an asterisk) and dramatically low cellular, axonal and myelinated axons density compared to PBS- (A) and melatonin-treated controls (D). Note the large proportion of myelinated axons surrounded with uncompacted myelin sheets (arrows) in PBS-treated GR-pups (B, C). In contrast, melatonin-treated GR animals exhibited a high proportion of well-compacted myelination processes, similar to controls (E–F). Interestingly, melatonin treatment appeared to not be able to restore a normal axonal aspect within the developing white matter (E). Swollen axons were marked with an asterisk. Quantitative analysis of myelin ultrastructural aspect was reported in table 2.