Document Detail

Intraglomerular inhibition maintains mitral cell response contrast across input frequencies.
MedLine Citation:
PMID:  23926045     Owner:  NLM     Status:  MEDLINE    
Odor signals are transmitted to the olfactory bulb by olfactory nerve (ON) synapses onto mitral/tufted cells (MTCs) and external tufted cells (ETCs); ETCs provide additional feed-forward excitation to MTCs. Both are strongly regulated by intraglomerular inhibition that can last up to 1 s and, when blocked, dramatically increases ON-evoked MC spiking. Intraglomerular inhibition thus limits the magnitude and duration of MC spike responses to sensory input. In vivo, sensory input is repetitive, dictated by sniffing rates from 1 to 8 Hz, potentially summing intraglomerular inhibition. To investigate this, we recorded MTC responses to 1- to 8-Hz ON stimulation in slices. Inhibitory postsynaptic current area (charge) following each ON stimulation was unchanged from 1 to 5 Hz and modestly paired-pulse attenuated at 8 Hz, suggesting there is no summation and only limited decrement at the highest input frequencies. Next, we investigated frequency independence of intraglomerular inhibition on MC spiking. MCs respond to single ON shocks with an initial spike burst followed by reduced spiking decaying to baseline. Upon repetitive ON stimulation peak spiking is identical across input frequencies but the ratio of peak-to-minimum rate before the stimulus (max-min) diminishes from 30:1 at 1 Hz to 15:1 at 8 Hz. When intraglomerular inhibition is selectively blocked, peak spike rate is unchanged but trough spiking increases markedly decreasing max-min firing ratios from 30:1 at 1 Hz to 2:1 at 8 Hz. Together, these results suggest intraglomerular inhibition is relatively frequency independent and can "sharpen" MC responses to input across the range of frequencies. This suggests that glomerular circuits can maintain "contrast" in MC encoding during sniff-sampled inputs.
Zuoyi Shao; Adam C Puche; Michael T Shipley
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Publication Detail:
Type:  Journal Article; Research Support, N.I.H., Extramural     Date:  2013-08-07
Journal Detail:
Title:  Journal of neurophysiology     Volume:  110     ISSN:  1522-1598     ISO Abbreviation:  J. Neurophysiol.     Publication Date:  2013 Nov 
Date Detail:
Created Date:  2013-11-04     Completed Date:  2014-06-20     Revised Date:  2014-11-04    
Medline Journal Info:
Nlm Unique ID:  0375404     Medline TA:  J Neurophysiol     Country:  United States    
Other Details:
Languages:  eng     Pagination:  2185-91     Citation Subset:  IM    
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MeSH Terms
Action Potentials*
Inhibitory Postsynaptic Potentials*
Mice, Inbred C57BL
Olfactory Bulb / cytology,  physiology*
Olfactory Nerve / cytology,  physiology
Grant Support

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