Impaired olfactory behavior in mice deficient in the alpha subunit of G(o).
The ability to respond to chemical signals is essential for the survival and reproduction of most organisms. Olfactory signaling involves odorant receptor-mediated activation of G(olf), a homologue of G(s), on the dendrites of olfactory neurons. Olfactory receptor cells, however, also express Galpha(i2) and Galpha(o) on their axons, with all neurons expressing G(o) and a subset G(i2). Despite their abundance, possible contributions of G(o) and G(i2) to chemoreception remain unexplored. We investigated whether homologous recombinant mice deficient in the alpha subunit of G(o) are able to respond to odorants, whether possible olfactory impairments are dependent on genetic background, and whether formation of glomeruli in their olfactory bulbs is compromised. In an olfactory habituation/dishabituation test, G(o)-/- mice were unresponsive when exposed to odorants. Analysis of variance shows that performance of G(o)+/- mice crossed into the CD-1 background is also diminished in this test compared to their G(o)+/+ counterparts. Following food deprivation, G(o)-/- mice in the 129 Sv-ter/C57BL/6 genetic background were unable to locate a buried food pellet until they were approximately 10 weeks of age after which they performed as well as their litter mate controls. However, CD-1 G(o)-/- mice could locate a buried food pellet even when tested immediately after weaning. Despite their compromised olfactory responsiveness, histological examination did not reveal gross alterations in the olfactory bulbs of G(o)-/- mice. Thus, Galpha(o) is necessary for the expression of olfactory behavior under normal conditions and dependent on genetic background, but is not essential for the formation and maintenance of glomeruli.
Luo
Alice H
AH
W.M. Keck Center for Behavioral Biology, North Carolina State University, Box 7617, Raleigh, NC 27695-7617, USA.
Cannon
Eliot H
EH
Wekesa
Kennedy S
KS
Lyman
Richard F
RF
Vandenbergh
John G
JG
Anholt
Robert R H
RR
D000704:Analysis of Variance; D000818:Animals; D001522:Behavior, Animal; D005260:Female; D044385:GTP-Binding Protein alpha Subunits; D020962:Heterotrimeric GTP-Binding Proteins / Q000172:deficiency* / Q000235:genetics; D007150:Immunohistochemistry; D008297:Male; D051379:Mice; D018345:Mice, Knockout; D009812:Odorants; D009830:Olfactory Bulb / Q000166:cytology; D018034:Olfactory Receptor Neurons; D010641:Phenotype; D012903:Smell / Q000235:genetics
D044385:GTP-Binding Protein alpha Subunits; C084618:olfactory G protein subunit alpha olf; D020962:Heterotrimeric GTP-Binding Proteins