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Olfactory bulb external tufted cells are synchronized by multiple intraglomerular mechanisms
Abdallah Hayar1, Michael T Shipley, Matthew Ennis
1Department of Anatomy and Neurobiology, University of Tennessee Health Science Center, Memphis, Tennessee 38163, USA. ahayar@utmem.edu
Summary
External tufted (ET) cells in the olfactory bulb synchronize via synaptic inputs and gap junctions. These mechanisms coordinate spontaneous bursting activity within the same glomerulus, crucial for olfactory processing.
Area of Science:
- Neuroscience
- Olfactory System Research
- Cellular Electrophysiology
Background:
- External tufted (ET) cells in the rat olfactory bulb spontaneously generate spike bursts.
- Synchronous activity is primarily observed between ET cells within the same glomerulus, indicating intraglomerular interactions.
- The specific intraglomerular mechanisms driving this synchrony remain largely unknown.
Purpose of the Study:
- To investigate the underlying intraglomerular mechanisms responsible for the synchronized bursting activity of external tufted (ET) cells.
- To elucidate how ET cells within the same glomerulus coordinate their spontaneous electrical activity.
Main Methods:
- Utilized dual extracellular and patch-clamp recordings from pairs of ET cells within the same glomerulus in rat olfactory bulb slices.
- Applied olfactory nerve stimulation and external plexiform layer stimulation to evoke synaptic responses.
- Employed synaptic blockers (CNQX, carbenoxolone) to differentiate between synaptic and gap junction-mediated mechanisms.
Main Results:
- ET cell pairs receive spontaneous synchronous fast excitatory synaptic input, also evoked by olfactory nerve stimulation.
- Correlated spontaneous slow excitatory synaptic currents, potentially involving glutamate spillover, were observed.
- Synchronous inhibitory postsynaptic currents (IPSCs) followed excitatory input, suggesting feedback inhibition from periglomerular cells.
- In the presence of synaptic blockers, ET cells showed synchronous slow membrane current oscillations and rhythmic spikelets sensitive to gap junction blockers.
Conclusions:
- Coordinated synaptic transmission, including fast excitation and slow excitation/inhibition, plays a key role in synchronizing ET cell bursting.
- Gap junction coupling contributes to the synchronized slow membrane current oscillations and spikelets between ET cells.
- These combined mechanisms ensure the coordinated activity of ET cells within a single glomerulus, impacting olfactory processing.