title: The involvement of spinal bovine adrenal medulla 22-like peptide, the proenkephalin derivative, in modulation of nociceptive processing.
abstract: 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.
authors.affiliation: Key Provincial Laboratory of Developmental Biology and Neuroscience, College of Life Sciences, Fujian Normal University, Fuzhou, People's Republic of China, 350108.
authors.forename: Meifang
authors.initials: M
authors.lastname: Cai
authors.forename: Tingjun
authors.initials: T
authors.lastname: Chen
authors.forename: Rémi
authors.initials: R
authors.lastname: Quirion
authors.forename: Yanguo
authors.initials: Y
authors.lastname: Hong
mesh_terms: D000818:Animals; D000906:Antibodies / Q000008:administration & dosage; D001522:Behavior, Animal; D004195:Disease Models, Animal; D004744:Enkephalin, Methionine / Q000031:analogs & derivatives* / Q000276:immunology / Q000378:metabolism; D005620:Freund's Adjuvant; D007839:Functional Laterality; D005727:Ganglia, Spinal / Q000166:cytology / Q000378:metabolism*; D005786:Gene Expression Regulation / Q000187:drug effects / Q000502:physiology; D008297:Male; D009474:Neurons / Q000378:metabolism; D016761:Oncogene Proteins v-fos / Q000378:metabolism; D010146:Pain / Q000139:chemically induced / Q000378:metabolism* / Q000473:pathology*; D010147:Pain Measurement; D011498:Protein Precursors / Q000276:immunology / Q000378:metabolism*; D051381:Rats; D019051:Rhizotomy / Q000379:methods; D013116:Spinal Cord / Q000378:metabolism*; D013119:Spinal Cord Injuries
chemical_list: D000906:Antibodies; D016761:Oncogene Proteins v-fos; D011498:Protein Precursors; D004744:Enkephalin, Methionine; C028837:BAM 22P; D005620:Freund's Adjuvant