title: Effects of tentacle amputation and regeneration on the morphology and activity of the olfactory center of the terrestrial slug Limax valentianus.
abstract: The tentacles of pulmonates regenerate spontaneously following amputation. The regenerated tentacle is equipped with all the elements necessary for normal olfactory functioning, and the slugs can behave as well as they did before the tentacle amputation. However, it is not known what changes occur to the olfactory center procerebrum in the brain at the morphological and physiological levels. Here, we investigated the innervation of tentacular nerves into the procerebrum by examining the size of the terminal mass (input layer from tentacular nerves) of the procerebrum and also by staining afferent nerves immunohistochemically at 15, 58 and 75 days following unilateral amputation of the superior and inferior tentacles. The size of the terminal mass was significantly decreased, and the Phe-Met-Arg-Phe-NH(2)ergic (FMRFamidergic) afferent nerves disappeared by 15 days following the tentacle amputation. However, the size of the terminal mass had recovered substantially by 58 days, as the tentacle regenerated. The FMRFamidergic innervation into the cerebral ganglion was also restored by this time. An extended recovery (75 days), however, did not result in any further increase in the size of the terminal mass. We also recorded the local field potential (LFP) oscillation in the procerebrum. We found that the oscillatory frequency of the LFP had decreased at 15 days following the tentacle amputation but had recovered at 58 and 75 days. These results suggest that the amputation and regrowth of the tentacle are accompanied by the respective degeneration and re-innervation of olfactory nerves, and these changes in the innervation status affect the basal state of LFP oscillation.
authors.affiliation: Kagawa School of Pharmaceutical Sciences, Tokushima Bunri University, Sanuki, Kagawa 769-2193, Japan. matsuor@kph.bunri-u.ac.jp
authors.forename: Ryota
authors.initials: R
authors.lastname: Matsuo
authors.forename: Suguru
authors.initials: S
authors.lastname: Kobayashi
authors.forename: Yoko
authors.initials: Y
authors.lastname: Tanaka
authors.forename: Etsuro
authors.initials: E
authors.lastname: Ito
mesh_terms: D000200:Action Potentials / Q000502:physiology; D000671:Amputation, Surgical; D000818:Animals; D001522:Behavior, Animal / Q000502:physiology; D004594:Electrophysiology; D019835:FMRFamide / Q000378:metabolism; D017952:Ganglia, Invertebrate / Q000033:anatomy & histology / Q000502:physiology; D049851:Gastropoda / Q000033:anatomy & histology / Q000502:physiology; D049990:Membrane Transport Modulators / Q000378:metabolism; D009833:Olfactory Pathways / Q000033:anatomy & histology / Q000502:physiology; D012038:Regeneration / Q000502:physiology*
chemical_list: D049990:Membrane Transport Modulators; D019835:FMRFamide