title: Opioid peptides in the nervous system of Aplysia: a combined biochemical, immunocytochemical, and electrophysiological study.
abstract: 1. We have used biochemical, immunocytochemical, and electrophysiological techniques to evaluate the role of opioid peptides in the central nervous system of the marine mollusc, Aplysia californica. 2. Binding studies using 3H-D-Ala2, met-enkephalinamide (3H-DAMA) showed a single class of high-affinity binding sites with a Kd of 1.3 nM and a binding density of 45 pmol/g. 3. HPLC extracts of ganglia revealed multiple peaks with immunoreactivity for either leu (LEU-IR)- or met-enkephalin (MET-IR), but the amounts were not uniformly distributed in all ganglia. 4. LEU-IR and MET-IR neurons were demonstrated immunocytochemically in all ganglia, but MET-IR neurons were more frequent and were concentrated in pedal and pleural ganglia. While absorption control studies abolished MET-IR, LEU-IR was only partially abolished in the neuropil. 5. In electrophysiological studies, both depolarizing and hyperpolarizing responses were found to D-Ala2-leu-enkephalin (DALEU) and D-Ala2-met enkephalin (DAMET) on some and different neurons. 6. HPLC fractions from regions with retention times corresponding to authentic leu- or met-enkephalin showed physiologic responses similar to those of DALEU and DAMET, respectively. 7. These studies suggest that a variety of endogeneous opioid peptides play physiologically important roles in the nervous system of Aplysia, including but not necessarily limited to leu- and met-enkephalin.
authors.affiliation: Wadsworth Center for Laboratories and Research, New York State Department of Health and School of Public Health, Albany 12201, USA.
authors.forename: D O
authors.initials: DO
authors.lastname: Carpenter
authors.forename: G
authors.initials: G
authors.lastname: Kemenes
authors.forename: K
authors.initials: K
authors.lastname: Elekes
authors.forename: M
authors.initials: M
authors.lastname: Leung
authors.forename: G
authors.initials: G
authors.lastname: Stefano
authors.forename: K S
authors.initials: KS
authors.lastname: Rózsa
authors.forename: J
authors.initials: J
authors.lastname: Salánki
mesh_terms: D000701:Analgesics, Opioid / Q000494:pharmacology; D000818:Animals; D001048:Aplysia; D004305:Dose-Response Relationship, Drug; D004594:Electrophysiology / Q000379:methods; D004743:Enkephalin, Leucine / Q000032:analysis*; D016308:Enkephalin, Leucine-2-Alanine / Q000031:analogs & derivatives / Q000494:pharmacology; D004744:Enkephalin, Methionine / Q000031:analogs & derivatives / Q000032:analysis* / Q000378:metabolism / Q000494:pharmacology; D017952:Ganglia, Invertebrate / Q000166:cytology* / Q000502:physiology*; D007150:Immunohistochemistry / Q000379:methods; D008564:Membrane Potentials / Q000187:drug effects; D009270:Naloxone / Q000494:pharmacology; D009292:Narcotic Antagonists / Q000494:pharmacology; D009474:Neurons / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D009928:Organ Specificity; D018408:Patch-Clamp Techniques; D011957:Receptors, Opioid / Q000378:metabolism
chemical_list: D000701:Analgesics, Opioid; D009292:Narcotic Antagonists; D011957:Receptors, Opioid; D009270:Naloxone; D004744:Enkephalin, Methionine; D004743:Enkephalin, Leucine; C021055:Met-enkephalinamide; C013801:enkephalin-Met, Ala(2)-; D016308:Enkephalin, Leucine-2-Alanine; C030279:enkephalinamide-Leu, Ala(2)-