Melanocortins and lesion-induced plasticity in the CNS: a review

This review summarises and critically evaluates the literature pertaining to the actions of short fragments of the adrenocorticotropic hormone (ACTH) ("melanocortins') on lesion-induced plasticity in the central nervous system (CNS). The majority of the evidence suggests that melanocortins are more effective in enhancing recovery from lesions of subcortical structures than cortical structures, although there is substantial variability in findings depending upon the specific ACTH fragment used and the way in which it is administered. Five specific melanocortin (MC) receptors have been identified, however, the evidence to date suggests that short ACTH fragments may not enhance lesion-induced plasticity in the CNS via these MC receptor subtypes. It is possible that another, as yet unidentified, MC receptor subtype is involved, or else that some short ACTH fragments act allosterically on another receptor type (e.g., the N-methyl-D-asparate (NMDA) receptor).