title: Group I metabotropic glutamate receptors are differentially expressed by two populations of olfactory bulb granule cells.
abstract: In the main olfactory bulb, several populations of granule cells (GCs) can be distinguished based on the soma location either superficially, interspersed with mitral cells within the mitral cell layer (MCL), or deeper, within the GC layer (GCL). Little is known about the physiological properties of superficial GCs (sGCs) versus deep GCs (dGCs). Here, we used patch-clamp recording methods to explore the role of Group I metabotropic glutamate receptors (mGluRs) in regulating the activity of GCs in slices from wildtype and mGluR-/- mutant mice. In wildtype mice, bath application of the selective Group I mGluR agonist DHPG depolarized and increased the firing rate of both GC subtypes. In the presence of blockers of fast synaptic transmission (APV, CNQX, gabazine), DHPG directly depolarized both GC subtypes, although the two GC subtypes responded differentially to DHPG in mGluR1-/- and mGluR5-/- mice. DHPG depolarized sGCs in slices from mGluR5-/- mice, although it had no effect on sGCs in slices from mGluR1-/- mice. By contrast, DHPG depolarized dGCs in slices from mGluR1-/- mice but had no effect on dGCs in slices from mGluR5-/- mice. Previous studies showed that mitral cells express mGluR1 but not mGluR5. The present results therefore suggest that sGCs are more similar to mitral cells than dGCs in terms of mGluR expression.
authors.affiliation: Dept. of Anatomy, Howard University College of Medicine, 520 W Street, NW, Washington, DC 20059, USA. theinbockel@howard.edu
authors.forename: Thomas
authors.initials: T
authors.lastname: Heinbockel
authors.forename: Kathryn A
authors.initials: KA
authors.lastname: Hamilton
authors.forename: Matthew
authors.initials: M
authors.lastname: Ennis
mesh_terms: D000818:Animals; D004247:DNA / Q000235:genetics; D004594:Electrophysiology; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D008734:Methoxyhydroxyphenylglycol / Q000031:analogs & derivatives / Q000494:pharmacology; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D009474:Neurons / Q000502:physiology*; D009830:Olfactory Bulb / Q000166:cytology / Q000502:physiology*; D018408:Patch-Clamp Techniques; D064529:Receptor, Metabotropic Glutamate 5; D018094:Receptors, Metabotropic Glutamate / Q000187:drug effects / Q000235:genetics / Q000502:physiology*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D009435:Synaptic Transmission / Q000187:drug effects
chemical_list: D018691:Excitatory Amino Acid Antagonists; C578936:Grm5 protein, mouse; D064529:Receptor, Metabotropic Glutamate 5; D018094:Receptors, Metabotropic Glutamate; C104077:metabotropic glutamate receptor type 1; D008734:Methoxyhydroxyphenylglycol; D004247:DNA; C010117:3,4-dihydroxyphenylglycol