title: Noradrenaline-induced enhancement of oscillatory local field potentials in the mouse accessory olfactory bulb does not depend on disinhibition of mitral cells.
abstract: The olfactory bulb differs from other brain regions by its use of bidirectional synaptic transmission at dendrodendritic reciprocal synapses. These reciprocal synapses provide tight coupling of inhibitory feedback from granule cell interneurons to mitral cell projection neurons in the accessory olfactory bulb (AOB), at the first stage of vomeronasal processing. It has been proposed that both the mGluR2 agonist DCG-IV and noradrenaline promote mate recognition memory formation by reducing GABAergic feedback on mitral cells. The resultant mitral cell disinhibition is thought to induce a long-lasting enhancement in the gain of inhibitory feedback from granule to mitral cells, which selectively gates the transmission of the learned chemosensory information. However, we found that local infusions of both noradrenaline and DCG-IV failed to disinhibit AOB neural activity in urethane-anaesthetised mice. DCG-IV infusion had similar effects to the GABA(A) agonist isoguvacine, suggesting that it increased GABAergic inhibition in the AOB rather than reducing it. Noradrenaline infusion into the AOB also failed to disinhibit mitral cells in awake mice despite inducing long-term increases in power of AOB local field potentials, similar to those observed following memory formation. These results suggest that mitral cell disinhibition is not essential for the neural changes in the AOB that underlie mate recognition memory formation in mice.
authors.affiliation: School of Physiology and Pharmacology, University of Bristol, Medical Sciences Building, University Walk, Bristol BS8 1TD, UK.
authors.forename: Emilia
authors.initials: E
authors.lastname: Leszkowicz
authors.forename: Selina
authors.initials: S
authors.lastname: Khan
authors.forename: Stephanie
authors.initials: S
authors.lastname: Ng
authors.forename: Nikita
authors.initials: N
authors.lastname: Ved
authors.forename: Daniel L
authors.initials: DL
authors.lastname: Swallow
authors.forename: Peter A
authors.initials: PA
authors.lastname: Brennan
mesh_terms: D018686:Anesthetics, Intravenous; D000818:Animals; D058256:Brain Waves / Q000187:drug effects*; D003521:Cyclopropanes / Q000494:pharmacology; D018690:Excitatory Amino Acid Agonists / Q000494:pharmacology; D005260:Female; D018755:GABA Agonists / Q000494:pharmacology; D005998:Glycine / Q000031:analogs & derivatives / Q000494:pharmacology; D007539:Isonicotinic Acids / Q000494:pharmacology; D051379:Mice; D008807:Mice, Inbred BALB C; D017551:Microdialysis; D009474:Neurons / Q000187:drug effects* / Q000502:physiology*; D009638:Norepinephrine / Q000494:pharmacology*; D009830:Olfactory Bulb / Q000166:cytology* / Q000502:physiology*; D014520:Urethane / Q000494:pharmacology; D014851:Wakefulness
chemical_list: D018686:Anesthetics, Intravenous; D003521:Cyclopropanes; D018690:Excitatory Amino Acid Agonists; D018755:GABA Agonists; D007539:Isonicotinic Acids; C082313:2-(2,3-dicarboxycyclopropyl)glycine; D014520:Urethane; D005998:Glycine; D009638:Norepinephrine; C015300:isoguvacine