Activation of β-noradrenergic receptors enhances rhythmic bursting in mouse olfactory bulb external tufted cells

Abstract

The main olfactory bulb (MOB) receives a rich noradrenergic innervation from the nucleus locus coeruleus. Despite the well-documented role of norepinephrine and β-adrenergic receptors in neonatal odor preference learning, identified cellular physiological actions of β-receptors in the MOB have remained elusive. β-Receptors are expressed at relatively high levels in the MOB glomeruli, the location of external tufted (ET) cells that exert an excitatory drive on mitral and other cell types. The present study investigated the effects of β-receptor activation on the excitability of ET cells with patch-clamp electrophysiology in mature mouse MOB slices. Isoproterenol and selective β-, but not β-, receptor agonists were found to enhance two key intrinsic currents involved in ET burst initiation: persistent sodium (I) and hyperpolarization-activated inward (I) currents. Together, the positive modulation of these currents increased the frequency and strength of ET cell rhythmic bursting. Rodent sniff frequency and locus coeruleus neuronal firing increase in response to novel stimuli or environments. The increase in ET excitability by β-receptor activation may better enable ET cell rhythmic bursting, and hence glomerular network activity, to pace faster sniff rates during heightened norepinephrine release associated with arousal.

Merkel Cells Activate Sensory Neural Pathways through Adrenergic Synapses

“…Dense-core vesicles package neuropeptides and small-molecule neurotransmitters such as monoamines, which are capable of exciting action potentials in neurons (Araneda and Firestein, 2006; Ramirez-Franco et al, 2016; Zhou et al, 2016). Monoamines include tryptophan-derived serotonin (5HT) and tyrosine-derived catecholamines, such as dopamine, epinephrine and norepinephrine.…”

Activation of Group II Metabotropic Glutamate Receptors Suppresses Excitability of Mouse Main Olfactory Bulb External Tufted and Mitral Cells

“…The prolonged depolarizations were absent in mitral cells lacking intact apical dendrites, suggesting a common glomerular origin with LLDs (Carlson et al, 2000 ). Candidate mechanisms that may generate these depolarization in synaptic blockers are: (1) an excitatory chemical transmitter released in the glomeruli, e.g., excitatory actions of glutamate acting at mGluR1 (Schoppa and Westbrook, 2001 ; Heinbockel et al, 2004 ; Yuan and Knopfel, 2006 ), cholecystokinin (Ma et al, 2013 ) or β adrenoreceptors (Nai et al, 2010 ; Zhou et al, 2016 ); and (2) an intrinsic membrane current such as a sustained sodium current; and/or depolarizations transmitted by electrical synapses between glutamatergic apical dendrites in the glomeruli (Schoppa and Westbrook, 2002 ; Christie et al, 2005 ; Hayar et al, 2005 ; Ma and Lowe, 2007 ; Pimentel and Margrie, 2008 ; De Saint Jan et al, 2009 ).…”

Complex neural representation of odour information in the olfactory bulb

“…The OB receives significant noradrenergic inputs from the locus coeruleus, which is known to play an important role in arousal, attention and emotional state. Norepinephrine dramatically changes the neural activity in a number of different bulbar cell types, including MCs, GCs and external tufted cells, etc . It activates multiple receptor sub‐types in the OB in a concentration‐dependent manner .…”