Alpha-MELANOCYTE stimulating hormone (alphaMSH) and Org 2766 (an adren
ocorticotrophic hormone (ACTH) MSH4-9 analogue) stimulate sprouting af
ter nerve damage in vivo. in cultures of rat spinal cord cells only al
phaMSH enhances neurite outgrowth. In order to analyse the mode of act
ion of alphaMSH and to get a clue why its action differs from that of
Org 2766, we studied whether expression of c-fos was induced in spinal
cord cells by treatment with alphaMSH or Org 2766. We found a rapid a
nd transient induction of both c-fos mRNA and protein after treatment
with 100 muM alphaMSH. Treatment with Org 2766 (100 pM-100 muM) had no
effect on c-fos expression. These results suggest that c-fos is invol
ved in the signal transduction system of alpha-MSH stimulated neuronal
outgrowth in vitro.