In their letter, Hyland et al report differences between data they obtained on mast cell phenotype and the role in visceral hypersensitivity to colorectal distension in adult rats previously submitted to maternal separation, and those we obtained using the same experimental protocol.1 They confirm the existence of colonic mast cell hyperplasia in maternally deprived rats, but they found it localised in the submucosa, while in our paper it was clearly localised in the mucosa. It has been shown that protease phenotype of mast cells and their locations in epithelium, lamina propria and …