Effect of alpha-melanocyte-stimulating hormone on peripheral nerve regeneration in the rat: histological aspects and comparison with the effect of gangliosides.

Recovery that follows a sciatic nerve crush was studied by counting the number of myelinated axons in cross sections of the sciatic nerve at various times after operation. Treatment with alpha-MSH (10 micrograms/animal, s.c., every 48 h) resulted in an increased number of myelinated axons 10 days after a sciatic nerve crush (3 mm distal to the crush). At postoperation day 22, alpha-MSH increased the number and diameter of axons 20 mm distal to the crush, but 3 mm distal to the crush no effect of alpha-MSH was seen. Treatment with gangliosides (50 mg/kg, i.p., daily) had a somewhat different effect: the number of axons was increased at a later stage and at all distances from the crush. The effect of gangliosides on the axonal diameter was opposite that of alpha-MSH: treatment with gangliosides stimulated the formation of axons with a smaller diameter.