title: cAMP-independent responses of olfactory neurons in Xenopus laevis tadpoles and their projection onto olfactory bulb neurons.
abstract: We report on responses of olfactory receptor neurons (ORNs) upon application of amino acids and forskolin using a novel slice preparation of the olfactory epithelium of Xenopus laevis tadpoles. Responses were measured using the patch-clamp technique. Both amino acids and forskolin proved to be potent stimuli. Interestingly, a number of ORNs that responded to amino acids did not respond to forskolin. This suggests that some amino acids activate transduction pathways other than the well-known cAMP-mediated one. The differential processing of cAMP-mediated stimuli on the one hand and amino acid stimuli on the other was further elucidated by calcium-imaging of olfactory bulb neurons using a novel nose-olfactory bulb preparation of Xenopus laevis tadpoles. The projection pattern of amino acid-sensitive ORNs to olfactory bulb neurons differed markedly from the projection pattern of forskolin-sensitive ORNs. Olfactory bulb neurons activated by amino acids were located laterally compared to those activated by forskolin, and only a small proportion responded to both stimuli. The ensemble of neurons activated by forskolin was also activated by the phosphodiesterase inhibitor 3-isobutyl-1-methylxanthine (IBMX) and the membrane-permeant cAMP analogue 8-(4-chlorophenylthio)adenosine 3',5'-cyclic monophosphate (pCPT-cAMP). We therefore conclude that sensory transduction of a number of amino acids is cAMP independent, and amino acid- and cAMP-mediated responses are processed differentially at the level of the olfactory bulb.
authors.affiliation: Physiologisches Institut, Universität Göttingen, Humboldtallee 23, 37073 Göttingen, Germany.
authors.forename: Ivan
authors.initials: I
authors.lastname: Manzini
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Rössler
authors.forename: Detlev
authors.initials: D
authors.lastname: Schild
mesh_terms: D000596:Amino Acids / Q000494:pharmacology; D000818:Animals; D005576:Colforsin / Q000494:pharmacology; D000242:Cyclic AMP / Q000502:physiology*; D006651:Histocytochemistry; D066298:In Vitro Techniques; D007814:Larva; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D009474:Neurons / Q000187:drug effects / Q000502:physiology*; D009666:Nose / Q000294:innervation / Q000502:physiology; D009812:Odorants; D009830:Olfactory Bulb / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D009833:Olfactory Pathways / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D018034:Olfactory Receptor Neurons / Q000187:drug effects / Q000502:physiology*; D018408:Patch-Clamp Techniques; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology; D014982:Xenopus laevis
chemical_list: D000596:Amino Acids; D005576:Colforsin; D000242:Cyclic AMP