Long-term orexigenic effects of AgRP-(83---132) involve mechanisms other than melanocortin receptor blockade.

Academic Article

Abstract

  • Overexpression of agouti-related peptide (AgRP), an endogenous melanocortin (MC) 3 and 4 receptor antagonist (MC3/4-R), causes obesity. Exogenous AgRP-(83---132) increases food intake, but its duration and mode of action are unknown. We report herein that doses as low as 10 pmol can have a potent effect on food intake of rats over a 24-h period after intracerebroventricular injection. Additionally, a single third ventricular dose as low as 100 pmol in rats produces a robust increase in food intake that persists for an entire week. AgRP-(83---132) completely blocks the anorectic effect of MTII (MC3/4-R agonist), given simultaneously, consistent with a competitive antagonist action. However, when given 24 h prior to MTII, AgRP-(83---132) is ineffective at reversing the anorectic effects of the agonist. These results support a critical role of MC tone in limiting food intake and indicate that the orexigenic effects of AgRP-(83---132) are initially mediated by competitive antagonism at MC receptors but are sustained by alternate mechanisms.
  • Authors

    Keywords

  • Agouti-Related Protein, Animals, Appetite Stimulants, Body Weight, Dose-Response Relationship, Drug, Eating, Intercellular Signaling Peptides and Proteins, Oligopeptides, Peptide Fragments, Proteins, Rats, Rats, Long-Evans, Receptor, Melanocortin, Type 3, Receptor, Melanocortin, Type 4, Receptors, Corticotropin, Time, alpha-MSH
  • Digital Object Identifier (doi)

    Author List

  • Hagan MM; Rushing PA; Pritchard LM; Schwartz MW; Strack AM; Van Der Ploeg LH; Woods SC; Seeley RJ
  • Start Page

  • R47
  • End Page

  • R52
  • Volume

  • 279
  • Issue

  • 1