Distribution of Met5-enkephalin-Arg6-Gly7-Leu8-immunoreactive Peptides in Rat Brain: Presence of Multiple Molecular Forms

Brain Res. 1984 May 7;299(1):73-8. doi: 10.1016/0006-8993(84)90789-3.


An antiserum to the opioid octapeptide met5-enk-arg6- gly7 -leu8 was used to measure the distribution and molecular weight heterogeneity of met5-enk-arg6- gly7 -leu8-immunoreactive (IR) peptides in rat brain. High concentrations of met5-enk-arg6- gly7 -leu8-IR peptides were found in the striatum and hypothalamus; low concentrations were observed in the cortex and cerebellum. Intermediate levels of immunoreactivity were found in other brain regions. Thus the distribution of met5-enk-arg6- gly7 -leu8-IR peptides closely parallels the distribution of met5-enkephalin. The immunoreactivity present in brain regions was characterized by gel filtration and reverse-phase high pressure liquid chromatography. In the striatum, more than 85% of the met5-enk-arg6- gly7 -leu8-IR peptides eluted from a Biogel P-30 column at the position of the authentic octapeptide; the identity of this material was further confirmed by HPLC. Gel filtration of extracts prepared from the medulla-pons resulted in two peaks of immunoreactive material of equal size; one eluted at approximately 8000 daltons and one eluted in the position of the octapeptide. Enzymatic digestion (trypsin + carboxypeptidase B) of the 8000 dalton-IR peptide resulted in the generation of met5-enkephalin-IR. Extracts prepared from other brain regions contained varying amounts of this high molecular weight form of met5-enk-arg6- gly7 -leu8.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • Brain / metabolism*
  • Chromatography, High Pressure Liquid
  • Enkephalin, Methionine / analogs & derivatives*
  • Enkephalin, Methionine / metabolism
  • Molecular Conformation
  • Molecular Weight
  • Radioimmunoassay
  • Rats


  • Enkephalin, Methionine
  • enkephalin-Met, Arg(6)-Gly(7)-Leu(8)-