title: Contrary effects of octopamine receptor ligands on behavioral and neuronal changes in locomotion of lymnaea.
abstract: The pond snail Lymnaea stagnalis moves along the sides and bottom of an aquarium, but it can also glide upside down on its back below the water's surface. We have termed these two forms of locomotion "standard locomotion" and "upside-down gliding," respectively. Previous studies showed that standard locomotion is produced by both cilia activity on the foot and peristaltic contraction of the foot muscles, whereas upside-down gliding is mainly caused by cilia activity. The pedal A neurons are thought to receive excitatory octopaminergic input, which ultimately results in increased cilia beating. However, the relationship between locomotory speed and the responses of these neurons to octopamine is not known. We thus examined the effects of both an agonist and an antagonist of octopamine receptors on locomotory speed and the firing rate of the pedal A neurons. We also examined, at the electron and light-microscopic levels, whether structural changes occur in cilia following the application of either an agonist or an antagonist of octopamine receptors to the central nervous system (CNS). We found that the application of an octopamine antagonist to the CNS increased the speed of both forms of locomotion, whereas application of octopamine increased only the firing rate of the pedal A neurons. Microscopic examination of the cilia proved that there were no changes in their morphology after application of octopamine ligands. These data suggest that there is an unidentified octopaminergic neuronal network in the CNS whose activation reduces cilia movement and thus locomotory speed.
authors.affiliation: Hokkaido Sapporo Okadama High School, Higashi-ku, Japan.
authors.forename: Yurie
authors.initials: Y
authors.lastname: Miyamae
authors.forename: Mami
authors.initials: M
authors.lastname: Komuro
authors.forename: Aya
authors.initials: A
authors.lastname: Murata
authors.forename: Kanako
authors.initials: K
authors.lastname: Aono
authors.forename: Kaori
authors.initials: K
authors.lastname: Nishikata
authors.forename: Akira
authors.initials: A
authors.lastname: Kanazawa
authors.forename: Yutaka
authors.initials: Y
authors.lastname: Fujito
authors.forename: Takumi
authors.initials: T
authors.lastname: Komatsu
authors.forename: Daisuke
authors.initials: D
authors.lastname: Ito
authors.forename: Takashi
authors.initials: T
authors.lastname: Abe
authors.forename: Masafumi
authors.initials: M
authors.lastname: Nagayama
authors.forename: Tsutomu
authors.initials: T
authors.lastname: Uchida
authors.forename: Kazutoshi
authors.initials: K
authors.lastname: Gohara
authors.forename: Jun
authors.initials: J
authors.lastname: Murakami
authors.forename: Ryo
authors.initials: R
authors.lastname: Kawai
authors.forename: Dai
authors.initials: D
authors.lastname: Hatakeyama
authors.forename: Ken
authors.initials: K
authors.lastname: Lukowiak
authors.forename: Etsuro
authors.initials: E
authors.lastname: Ito
mesh_terms: D000818:Animals; D002923:Cilia / Q000648:ultrastructure; D008024:Ligands; D008124:Locomotion / Q000187:drug effects*; D008195:Lymnaea / Q000187:drug effects* / Q000648:ultrastructure; D008853:Microscopy; D046529:Microscopy, Electron, Transmission; D017982:Receptors, Biogenic Amine / Q000819:agonists* / Q000037:antagonists & inhibitors* / Q000187:drug effects
chemical_list: D008024:Ligands; D017982:Receptors, Biogenic Amine; C027604:norsynephrine receptor