Serotonin increases synaptic activity in olfactory bulb glomeruli.

Content Provider	Semantic Scholar
Author	Brill, Julia A. Shao, Zuoyi Puche, Adam C. Wachowiak, Matt Shipley, Michael T.
Copyright Year	2016
Abstract	Serotoninergic fibers densely innervate olfactory bulb glomeruli, the first sites of synaptic integration in the olfactory system. Acting through 5HT2A receptors, serotonin (5HT) directly excites external tufted cells (ETCs), key excitatory glomerular neurons, and depolarizes some mitral cells (MCs), the olfactory bulb's main output neurons. We further investigated 5HT action on MCs and determined its effects on the two major classes of glomerular interneurons: GABAergic/dopaminergic short axon cells (SACs) and GABAergic periglomerular cells (PGCs). In SACs, 5HT evoked a depolarizing current mediated by 5HT2C receptors but did not significantly impact spike rate. 5HT had no measurable direct effect in PGCs. Serotonin increased spontaneous excitatory and inhibitory postsynaptic currents (sEPSCs and sIPSCs) in PGCs and SACs. Increased sEPSCs were mediated by 5HT2A receptors, suggesting that they are primarily due to enhanced excitatory drive from ETCs. Increased sIPSCs resulted from elevated excitatory drive onto GABAergic interneurons and augmented GABA release from SACs. Serotonin-mediated GABA release from SACs was action potential independent and significantly increased miniature IPSC frequency in glomerular neurons. When focally applied to a glomerulus, 5HT increased MC spontaneous firing greater than twofold but did not increase olfactory nerve-evoked responses. Taken together, 5HT modulates glomerular network activity in several ways: 1) it increases ETC-mediated feed-forward excitation onto MCs, SACs, and PGCs; 2) it increases inhibition of glomerular interneurons; 3) it directly triggers action potential-independent GABA release from SACs; and 4) these network actions increase spontaneous MC firing without enhancing responses to suprathreshold sensory input. This may enhance MC sensitivity while maintaining dynamic range.
Starting Page	5
Ending Page	9
Page Count	5
File Format	PDF HTM / HTML
Alternate Webpage(s)	http://jn.physiology.org/content/jn/115/3/1208.full.pdf
PubMed reference number	26655822v1
Alternate Webpage(s)	https://doi.org/10.1152/jn.00847.2015
DOI	10.1152/jn.00847.2015
Journal	Journal of neurophysiology
Volume Number	115
Issue Number	3
Language	English
Access Restriction	Open
Subject Keyword	Axon CNS disorder Class Dopamine Hydrochloride Excitation Gonadotropin-Releasing Hormone Receptor Inhibitory Postsynaptic Currents Interneurons Kidney Glomerulus Olfactory Nerve Postsynaptic Current Precipitating Factors Structure of olfactory bulb Tissue fiber gamma-Aminobutyric Acid serotonin receptor
Content Type	Text
Resource Type	Article