Specificity versus redundancy of melanocortins in nerve regeneration

F. J. Antonawich, Efrain Azmitia, H. K. Kramer, F. L. Strand

Research output: Contribution to journalArticle

Abstract

The results of the present study demonstrate that administration of the ACTH-(4-9) analogue Org 2766 acutely enhances behavioral, morphological, and biochemical recovery after nigrostriatal destruction. Animals created with Org 2766 (10 μg/kg every 24 hr) demonstrated an acceleration of denervation supersensitivity and a significantly decreased ipsilateral rotational response, as compared to their saline counterparts. Upon evaluation of the mesolimbic DA system using open field behavior, peptide-treated rats demonstrated a compensatory response in their rearing behavior. Furthermore, tyrosine hydroxylase immunocytochemical analysis indicated an enhanced staining in the Org 2766-treated groups. This evaluation was confirmed and quantified using specific high-affinity dopamine uptake. The brains of animals treated with Org 2766 maintained higher uptake levels, suggesting a greater fiber density than the saline-treated animals. Although recovery via reinnervation is very unlikely in this short period of time, improved recovery may be the result of a protective effect of Org 2766 after administration of 6-OHDA into the substantia nigra. Thus, it appears that Org 2766 provides the rapid effects in this system, by both accelerating some compensatory mechanisms necessary for functional recovery and promoting cell survival by providing neuronal protection. However, it does not appear that this protection is due to NMDA receptor manipulation. Org 2766 neither mimicked the NMDA antagonist MK-801 behaviorally nor biochemically in binding displacement studies. Interestingly, other studies have suggested that only the full ACTH molecule, and fragments larger than ACTH-(1-17), demonstrated binding activity at micromolar concentrations, whereas the shorter, noncorticotropic fragments were either less active or inactive. As for ACTH-(4-10) immunoreactivity, it appears that this neurotrophic fragment of ACTH reappears in adults following injury to the nigrostriatal system. In addition, the systemically administered ACTH-(4-9) analogue, Org 2766, seems to be gaining access to the CNS, but is only effective in the injured system. Therefore, based on the immunocytochemical localization of the ACTH-(4-10) fragment in neonatal brains and in the injured adult rat CNS, the interesting possibility may be raised that endogenous ACTH peptides appear during both ontogeny and regeneration. These studies demonstrate once again that biological responses to the family of ACTH/MSH peptides depend on the specific peptide fragment administered, its dosage, and the timing of the administration. Consequently, since early intervention is of vital importance in CNS recovery processes, synergistic administration of ACTH fragments and other neurotrophic agents may offer a viable approach with which to combat degeneration in the CNS.

Original languageEnglish (US)
Pages (from-to)60-73
Number of pages14
JournalAnnals of the New York Academy of Sciences
Volume739
StatePublished - 1994

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Melanocortins
Nerve Regeneration
Redundancy
Adrenocorticotropic Hormone
ACTH (4-10)
Recovery
Animals
Peptides
Rats
Brain
Melanocyte-Stimulating Hormones
Peptide Fragments
Dizocilpine Maleate
Org 2766
Specificity
Nerve
Regeneration
Oxidopamine
Open systems
Tyrosine 3-Monooxygenase

ASJC Scopus subject areas

  • Biochemistry, Genetics and Molecular Biology(all)

Cite this

Specificity versus redundancy of melanocortins in nerve regeneration. / Antonawich, F. J.; Azmitia, Efrain; Kramer, H. K.; Strand, F. L.

In: Annals of the New York Academy of Sciences, Vol. 739, 1994, p. 60-73.

Research output: Contribution to journalArticle

Antonawich, F. J. ; Azmitia, Efrain ; Kramer, H. K. ; Strand, F. L. / Specificity versus redundancy of melanocortins in nerve regeneration. In: Annals of the New York Academy of Sciences. 1994 ; Vol. 739. pp. 60-73.
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