title: Identification and localization of a [Met5]-enkephalin-like peptide in the mollusc, Lymnaea stagnalis.
abstract: The goal of this study was to determine whether [Met5]-enkephalin, or an analog, is present in identified neurons in the central nervous system (CNS) of the freshwater snail, Lymnaea stagnalis. High performance liquid chromatography and radioimmunoassay of CNS tissue homogenates revealed both [Met5]-enkephalin and oxidized [Met5]-enkephalin. NO [Leu5]-enkephalin, [Met5]-enkephalin-Arg6-Phe7 or [Met5]-enkephalin-Arg6-Gly7-Leu8 were detected. Quantification of [Met5]-enkephalin, by radioimmunoassay, revealed that the Lymnaea CNS contains approximately 2.2 fmol/CNS (undigested tissue) and 4.5 fmol/CNS (tissue enzymatically digested with trypsin and carboxypeptidase B). The increased amount of [Met5]-enkephalin following tissue digestion indicates the presence of as yet unidentified extended forms of [Met5]-enkephalin in Lymnaea. Using indirect immunocytochemistry, a [Met5]-enkephalin-like peptide was localized to individual cells and cell clusters within the CNS, as well as to fibers in the atrium of the heart. A neuronal map depicting [Met5]-enkephalin-like immunoreactive cells was produced. Among the immunoreactive neurons were four identified, well-characterized, giant cells: VD1, RPD2, LB1 and RB1. Identifiable [Met5]-enkephalin-like immunoreactive neurons were characterized electrophysiologically and morphologically. Additionally, neurons VD1 and RPD2 were confirmed to be immunoreactive to Lymnaea alpha-peptide. The lack of both cross reactivity and sequence homology between alpha-peptide and [Met5]-enkephalin suggests that a [Met5]-enkephalin-like peptide and alpha-peptide are co-localized within these neurons.
authors.affiliation: Department of Medical Physiology, University of Calgary, Alberta, Canada.
authors.forename: N M
authors.initials: NM
authors.lastname: Ewadinger
authors.forename: R L
authors.initials: RL
authors.lastname: Ridgway
authors.forename: N I
authors.initials: NI
authors.lastname: Syed
authors.forename: K
authors.initials: K
authors.lastname: Lukowiak
authors.forename: A G
authors.initials: AG
authors.lastname: Bulloch
mesh_terms: D000818:Animals; D000918:Antibody Specificity; D002851:Chromatography, High Pressure Liquid; D003429:Cross Reactions; D004594:Electrophysiology; D004744:Enkephalin, Methionine / Q000032:analysis* / Q000276:immunology; D005455:Fluorescent Antibody Technique; D006325:Heart Atria / Q000737:chemistry; D015151:Immunoblotting; D008195:Lymnaea / Q000737:chemistry*; D009206:Myocardium / Q000737:chemistry; D009474:Neurons / Q000737:chemistry / Q000502:physiology; D018847:Opioid Peptides / Q000032:analysis; D011863:Radioimmunoassay
chemical_list: D018847:Opioid Peptides; D004744:Enkephalin, Methionine