title: Octopamine modulates ionic currents and spiking in dorsal unpaired median (DUM) neurons.
abstract: Modulatory effects of octopamine on ionic currents and spiking in isolated cockroach dorsal unpaired median neurons were investigated by means of the chopped voltage-/current-clamp and the patch-clamp technique. Octopamine increased the spiking frequency at concentrations < or = 10 microM and reduced it at > 10 microM. It enhanced a low voltage-activated Ca2+ current at 1 to 100 microM. At concentrations up to 10 microM two components of Ca2+-activated K+ current were potentiated. At > 10 microM octopamine in addition reduced a high voltage-activated Ca2+ current and the Ca2+-activated K+ current. A membrane permeant cAMP-analogue imitated the effects obtained at high octopamine concentration. Octopamine and cAMP in addition reduced a depolarizing resting current at both low and high concentration. Possible mechanisms and physiological significance are discussed for the opposite effects of octopamine observed at low versus high concentrations.
authors.affiliation: Institut für Normale und Pathologische Physiologie, Abt. Neuroendokrinologie, Philipps-Universität Marburg, Germany.
authors.forename: H
authors.initials: H
authors.lastname: Achenbach
authors.forename: C
authors.initials: C
authors.lastname: Walther
authors.forename: D
authors.initials: D
authors.lastname: Wicher
mesh_terms: D015124:8-Bromo Cyclic Adenosine Monophosphate / Q000494:pharmacology; D000200:Action Potentials / Q000187:drug effects / Q000502:physiology; D000818:Animals; D015220:Calcium Channels / Q000187:drug effects / Q000502:physiology*; D003058:Cockroaches; D000242:Cyclic AMP / Q000494:pharmacology / Q000502:physiology; D017952:Ganglia, Invertebrate / Q000502:physiology*; D066298:In Vitro Techniques; D009474:Neurons / Q000187:drug effects / Q000502:physiology*; D009655:Octopamine / Q000494:pharmacology*; D015221:Potassium Channels / Q000187:drug effects / Q000502:physiology*; D013779:Tetrodotoxin / Q000494:pharmacology
chemical_list: D015220:Calcium Channels; D015221:Potassium Channels; D009655:Octopamine; D015124:8-Bromo Cyclic Adenosine Monophosphate; D013779:Tetrodotoxin; D000242:Cyclic AMP