title: Confinement but not microgravity alters NMDA NR1 receptor expression in rat inner ear ganglia.
abstract: Space flight produces changes in neuronal activity in the vestibular system. We studied the protein expression of the NMDA receptor subunit NR1 in the vestibular ganglia of rats exposed to microgravity for 17 days, beginning on postnatal day 8, as part of the NASA Neurolab mission. As a control, we studied the cochlear ganglia in the same way. NR1 expression in rats that had experienced microgravity (flight-FLT rats) was compared with that in two types of ground control. One control consisted of rats housed in regular cage conditions (VIV, vivarium); the other, asynchronous ground control (AGC), consisted of rats kept in cages similar to those used in flight (animal enclosure module, AEM), requiring no human care. After 8 days of flight, NR1 levels in the vestibular and cochlear neurons were similar in FLT, VIV and AGC rats. In contrast, 8 h after landing, the FLT and VIV animals showed similar, normal levels of NR1 staining, whereas the ganglia of the AGC animals displayed only very faint staining. Thus, microgravity did not modify NR1 expression in vestibular neurons. The lower levels of NR1 expression in the vestibular and cochlear neurons of AGC rats suggest an effect of confinement for 17 days in AEMs on the ground.
authors.affiliation: INSERM U432, Université de Montpellier II, Place Bataillon, 34095 Montpellier, France. claudejd@univ-montp2-fr
authors.forename: Claude J
authors.initials: CJ
authors.lastname: Dechesne
authors.forename: Pierre G
authors.initials: PG
authors.lastname: Milhaud
authors.forename: Danielle
authors.initials: D
authors.lastname: Demêmes
authors.forename: Stéphanie
authors.initials: S
authors.lastname: Ventéo
authors.forename: Florence
authors.initials: F
authors.lastname: Gaven
authors.forename: Jacqueline
authors.initials: J
authors.lastname: Raymond
mesh_terms: D000818:Animals; D017626:Cochlear Nucleus / Q000378:metabolism*; D020378:Confined Spaces; D007150:Immunohistochemistry; D008297:Male; D051381:Rats; D017207:Rats, Sprague-Dawley; D016194:Receptors, N-Methyl-D-Aspartate / Q000378:metabolism*; D013026:Space Flight; D014726:Vestibular Nuclei / Q000378:metabolism*; D014893:Weightlessness
chemical_list: D016194:Receptors, N-Methyl-D-Aspartate