Combined trypan blue and formaldehyde-induced fluorescence in experimental skin freezing in the rat.

In order to study the effects of skin freezing in the rat on cutaneous vasculature and adrenergic nerves, a combination of trypan blue and formaldehyde-induced catecholamine fluorescence was used. It was shown that trypan blue clearly demonstrates both hyperaemic and ischaemic areas as well as changes in blood cessel permeability after experimental cold injury. Combination of the two fluorescence methods made it possible to correlate rough changes in blood vessel flow and permeability with changes in adrenergic nerves. Twentyfour hours after freezing of the skin, denervation of the most seriously damaged area was apparent. At the border of the cold injury, signs suggesting accumulation of actecholamines were observed in the subcutaneous nerves.