The involvement of spinal bovine adrenal medulla 22-like peptide, the proenkephalin derivative, in modulation of nociceptive processing

Eur J Neurosci. 2007 Sep;26(5):1128-38. doi: 10.1111/j.1460-9568.2007.05755.x.


Bovine adrenal medulla 22 (BAM22), one of the cleavage products of proenkephalin A, possesses high affinity for opioid receptors and sensory neuron-specific receptor (SNSR). The present study was designed to examine the expression of BAM22 in the spinal cord and dorsal root ganglion (DRG) of naive rats as well as in a model of inflammation. BAM22-like immunoreactivity (BAM22-IR) was expressed in fibers in the spinal cord, with high density seen in lamina I in naïve rats. The expression of BAM22-IR in the superficial laminae was greatly reduced following dorsal rhizotomy. BAM22-IR was also located in 19% of DRG cells, mainly in the small- and medium-sized subpopulations. Following injection of complete Freund's adjuvant (CFA) in the hindpaw, the expression of BAM22-IR in the superficial laminae of the spinal cord and small-sized DRG neurons on the ipsilateral side was markedly increased. Double labeling showed that the Fos-positive nucleus was surrounded by BAM22-IR cytoplasm in the spinal dorsal horn neurons or closely associated with BAM22-IR fibers in the superficial laminae. Furthermore, CFA-induced mechanical allodynia in the inflamed paw was potentiated by intrathecal administration of anti-BAM22 antibody. Together, these results demonstrate for the first time that BAM22-like peptide is mainly located in the superficial laminae of the spinal cord and mostly originates from nociceptive DRG neurons. BAM22 could thus act as a ligand for presynaptic opioid receptors and SNSR. Our study also provides evidence suggesting that BAM22 plays a role in the modulation of nociceptive processing at the spinal level under normal and inflammatory conditions.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Antibodies / administration & dosage
  • Behavior, Animal
  • Disease Models, Animal
  • Enkephalin, Methionine / analogs & derivatives*
  • Enkephalin, Methionine / immunology
  • Enkephalin, Methionine / metabolism
  • Freund's Adjuvant
  • Functional Laterality
  • Ganglia, Spinal / cytology
  • Ganglia, Spinal / metabolism*
  • Gene Expression Regulation / drug effects
  • Gene Expression Regulation / physiology
  • Male
  • Neurons / metabolism
  • Oncogene Proteins v-fos / metabolism
  • Pain / chemically induced
  • Pain / metabolism*
  • Pain / pathology*
  • Pain Measurement
  • Protein Precursors / immunology
  • Protein Precursors / metabolism*
  • Rats
  • Rhizotomy / methods
  • Spinal Cord / metabolism*
  • Spinal Cord Injuries


  • Antibodies
  • Oncogene Proteins v-fos
  • Protein Precursors
  • Enkephalin, Methionine
  • BAM 22P
  • Freund's Adjuvant