Journal
JOURNAL OF NEUROPHYSIOLOGY
Volume 89, Issue 5, Pages 2466-2472Publisher
AMER PHYSIOLOGICAL SOC
DOI: 10.1152/jn.00997.2002
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Funding
- NIDCD NIH HHS [1F31-DC-05124-01] Funding Source: Medline
- NINDS NIH HHS [NS-26494] Funding Source: Medline
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Dendrodendritic synapses, distributed along mitral cell lateral dendrites, provide powerful and extensive inhibition in the olfactory bulb. Activation of inhibition depends on effective penetration of action potentials into dendrites. Although action potentials backpropagate with remarkable fidelity in apical dendrites, this issue is controversial for lateral dendrites. We used paired somatic and dendritic recordings to measure action potentials in proximal dendritic segments (0-200 mum from soma) and action potential-generated calcium transients to monitor activity in distal dendritic segments (200-600 mum from soma). Somatically elicited action potentials were attenuated in proximal lateral dendrites. The attenuation was not due to impaired access resistance in dendrites or to basal synaptic activity. However, a single somatically elicited action potential was sufficient to evoke a calcium transient throughout the lateral dendrite, suggesting that action potentials reach distal dendritic compartments. Block of A-type potassium channels (I-A) with 4-aminopyridine (10 mM) prevented action potential attenuation in direct recordings and significantly increased dendritic calcium transients, particularly in distal dendritic compartments. Our results suggest that I-A may regulate inhibition in the olfactory bulb by controlling action potential amplitudes in lateral dendrites.
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