The enhanced recovery of sensorimotor function in rats is related to the melanotropic moiety of ACTH/MSH neuropeptides.

The recovery of sensorimotor function in female rats was studied using a foot-flick response test after crushing the sciatic nerve. Every other day the animals received a subcutaneous injection of small ACTH/MSH-like peptides. Rats treated with ACTH-(4-10), ACTH-(4-9), ACTH-(4-9) analog ORG 2766, ACTH-(6-10) and alpha-MSH showed a faster recovery of sensorimotor function as compared to vehicle-treated rats. Treatment with ACTH-(4-7) and the tripeptide Phe7-D-Lys8-Phe9 (PDLP, the C-terminal part of the ORG 2766) remained ineffective. The effect of alpha-MSH was even stronger than that of the other peptides. The facilitation of the return of sensorimotor function by the ACTH-like peptides is discussed in relation to the corticotropic and melanotropic properties of these peptides. Furthermore, it was shown that treatment with ORG 2766 was effective not only in young adult animals (2--3 months) but also in one-year-old animals.