title: Multilevel inhibition of feeding by a peptidergic pleural interneuron in the mollusc Lymnaea stagnalis.
abstract: The pleural interneuron PlB is a white neuron in the pleural ganglion of the snail Lymnaea. We test the hypothesis that it inhibits neurons at all levels of the feeding system, using a combination of anatomy, physiology and pharmacology. There is just one PlB in each pleural ganglion. Its axon traverses the pedal and cerebral ganglia, running into the buccal ganglia. It has neuropilar branches in the regions of the cerebral and buccal ganglia where neurons that are active during feeding also branch. Activation of the PlB blocks fictive feeding, whether the feeding rhythm occurs spontaneously or is driven by a modulatory interneuron. The PlB inhibits all the neurons in the feeding network, including protraction and retraction motoneurons, central pattern generator interneurons, buccal modulatory interneurons (SO, OC), and cerebral modulatory interneurons (CV1, CGC). Only the CV1 interneuron shows discrete 1:1 IPSPs; all other effects are slow, smooth hyperpolarizations. All connections persist in Ca(2+)/Mg(2+)-rich saline, which reduces polysynaptic effects. The inhibitory effects are mimicked by 0.5 to 100 micromol l(-1) FMRFamide, which the PlB soma contains. We conclude that the PlB inhibits neurons in the feeding system at all levels, probably acting though the peptide transmitter FMRFamide.
authors.affiliation: Faculty of Biology, Laboratory of Physiology and Pathology of Brain, Tbilisi State University, University str. 2., 380043 Tbilisi, Georgia.
authors.forename: M
authors.initials: M
authors.lastname: Alania
authors.forename: D A
authors.initials: DA
authors.lastname: Sakharov
authors.forename: C J H
authors.initials: CJ
authors.lastname: Elliott
mesh_terms: D000200:Action Potentials / Q000187:drug effects / Q000502:physiology; D000818:Animals; D001369:Axons / Q000187:drug effects / Q000378:metabolism / Q000648:ultrastructure; D002118:Calcium / Q000378:metabolism / Q000494:pharmacology; D002490:Central Nervous System / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D019835:FMRFamide / Q000378:metabolism / Q000494:pharmacology; D005247:Feeding Behavior / Q000187:drug effects / Q000502:physiology*; D017952:Ganglia, Invertebrate / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D066298:In Vitro Techniques; D007395:Interneurons / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D007546:Isoquinolines; D008195:Lymnaea / Q000166:cytology / Q000378:metabolism*; D008274:Magnesium / Q000378:metabolism / Q000494:pharmacology; D009415:Nerve Net / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D009433:Neural Inhibition / Q000187:drug effects / Q000502:physiology*; D009434:Neural Pathways / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D009479:Neuropeptides / Q000378:metabolism*; D010507:Periodicity; D009435:Synaptic Transmission / Q000187:drug effects / Q000502:physiology
chemical_list: D007546:Isoquinolines; D009479:Neuropeptides; D019835:FMRFamide; C017475:lucifer yellow; D008274:Magnesium; D002118:Calcium