title: Functional changes in the snail statocyst system elicited by microgravity.
abstract: BACKGROUND
  The mollusk statocyst is a mechanosensing organ detecting the animal's orientation with respect to gravity. This system has clear similarities to its vertebrate counterparts: a weight-lending mass, an epithelial layer containing small supporting cells and the large sensory hair cells, and an output eliciting compensatory body reflexes to perturbations.
  
  
  RESULTS
  In terrestrial gastropod snail we studied the impact of 16- (Foton M-2) and 12-day (Foton M-3) exposure to microgravity in unmanned orbital missions on: (i) the whole animal behavior (Helix lucorum L.), (ii) the statoreceptor responses to tilt in an isolated neural preparation (Helix lucorum L.), and (iii) the differential expression of the Helix pedal peptide (HPep) and the tetrapeptide FMRFamide genes in neural structures (Helix aspersa L.). Experiments were performed 13-42 hours after return to Earth. Latency of body re-orientation to sudden 90° head-down pitch was significantly reduced in postflight snails indicating an enhanced negative gravitaxis response. Statoreceptor responses to tilt in postflight snails were independent of motion direction, in contrast to a directional preference observed in control animals. Positive relation between tilt velocity and firing rate was observed in both control and postflight snails, but the response magnitude was significantly larger in postflight snails indicating an enhanced sensitivity to acceleration. A significant increase in mRNA expression of the gene encoding HPep, a peptide linked to ciliary beating, in statoreceptors was observed in postflight snails; no differential expression of the gene encoding FMRFamide, a possible neurotransmission modulator, was observed.
  
  
  CONCLUSIONS
  Upregulation of statocyst function in snails following microgravity exposure parallels that observed in vertebrates suggesting fundamental principles underlie gravi-sensing and the organism's ability to adapt to gravity changes. This simple animal model offers the possibility to describe general subcellular mechanisms of nervous system's response to conditions on Earth and in space.
authors.affiliation: Institute of Higher Nervous Activity and Neurophysiology, Russian Academy of Sciences, Moscow, Russia.
authors.forename: Pavel M
authors.initials: PM
authors.lastname: Balaban
authors.forename: Aleksey Y
authors.initials: AY
authors.lastname: Malyshev
authors.forename: Victor N
authors.initials: VN
authors.lastname: Ierusalimsky
authors.forename: Nikolay
authors.initials: N
authors.lastname: Aseyev
authors.forename: Tania A
authors.initials: TA
authors.lastname: Korshunova
authors.forename: Natasha I
authors.initials: NI
authors.lastname: Bravarenko
authors.forename: M S
authors.initials: MS
authors.lastname: Lemak
authors.forename: Matvey
authors.initials: M
authors.lastname: Roshchin
authors.forename: Igor S
authors.initials: IS
authors.lastname: Zakharov
authors.forename: Yekaterina
authors.initials: Y
authors.lastname: Popova
authors.forename: Richard
authors.initials: R
authors.lastname: Boyle
mesh_terms: D000825:Animal Structures / Q000502:physiology*; D000818:Animals; D001522:Behavior, Animal / Q000502:physiology; D002490:Central Nervous System / Q000502:physiology; D055724:Electrophysiological Phenomena; D005786:Gene Expression Regulation; D009474:Neurons / Q000166:cytology / Q000378:metabolism; D012908:Snails / Q000235:genetics / Q000502:physiology*; D013026:Space Flight; D014893:Weightlessness