title: Tonic and stimulus-evoked nitric oxide production in the mouse olfactory bulb.
abstract: Nitric oxide (NO) has been long assumed to play a key role in mammalian olfaction. This was based largely on circumstantial evidence, i.e. prominent staining for nitric oxide synthase (NOS) and cyclic guanosine 3',5'-cyclic monophosphate (cGMP) or soluble guanylyl cyclase, an effector enzyme activated by NO, in local interneurons of the olfactory bulb. Here we employ innovative custom-fabricated NO micro-sensors to obtain the first direct, time-resolved measurements of NO signaling in the olfactory bulb. In 400 microm thick mouse olfactory bulb slices, we detected a steady average basal level of 87 nM NO in the extracellular space of mitral or granule cell layers. This NO 'tone' was sensitive to NOS substrate manipulation (200 microM L-arginine, 2 mM N(G)-nitro-L-arginine methyl ester) and Mg(2+) modulation of N-methyl-D-aspartate (NMDA) receptor conductance. Electrical stimulation of olfactory nerve fibers evoked transient (peak at 10 s) increments in NO levels 90-100 nM above baseline. In the anesthetized mouse, NO micro-sensors inserted into the granule cell layer detected NO transients averaging 55 nM in amplitude and peaking at 3.4 s after onset of a 5 s odorant stimulation. These findings suggest dual roles for NO signaling in the olfactory bulb: tonic inhibitory control of principal neurons, and regulation of circuit dynamics during odor information processing.
authors.affiliation: Monell Chemical Senses Center, Philadelphia, PA 19104-3308, USA. loweg@monell.org
authors.forename: G
authors.initials: G
authors.lastname: Lowe
authors.forename: D G
authors.initials: DG
authors.lastname: Buerk
authors.forename: J
authors.initials: J
authors.lastname: Ma
authors.forename: A
authors.initials: A
authors.lastname: Gelperin
mesh_terms: D000818:Animals; D004558:Electric Stimulation; D051379:Mice; D008839:Microelectrodes; D009474:Neurons / Q000378:metabolism; D009569:Nitric Oxide / Q000378:metabolism*; D009830:Olfactory Bulb / Q000378:metabolism*; D055696:Olfactory Perception / Q000502:physiology*; D015398:Signal Transduction / Q000502:physiology*
chemical_list: D009569:Nitric Oxide