Afterhyperpolarization (AHP) regulates the frequency and timing of action potentials in the mitral cells of the olfactory bulb: role of olfactory experience. Issue 5 (May 2015)

• Record Type: Journal Article
• Authors: Duménieu, Maël; Fourcaud‐Trocmé, Nicolas; Garcia, Samuel; Kuczewski, Nicola
• Is Part Of: Physiological reports. Volume 3:Issue 5(2015:May)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2015-05
• Subjects: Firing -- intrinsic plasticity -- recurrent synaptic transmission; Physiology -- Periodicals; 571
• DOI: 10.14814/phy2.12344
• Languages: English
• ISSNs: 2051-817X

Abstract

Abstract: Afterhyperpolarization (AHP) is a principal feedback mechanism in the control of the frequency and patterning of neuronal firing. In principal projection neurons of the olfactory bulb, the mitral cells (MCs), the AHP is produced by three separate components: classical potassium‐mediated hyperpolarization, and the excitatory and inhibitory components, which are generated by the recurrent dendrodendritic synaptic transmission. Precise spike timing is involved in olfactory coding and learning, as well as in the appearance of population oscillatory activity. However, the contribution of the AHP and its components to these processes remains unknown. In this study, we demonstrate that the AHP is developed with the MC firing frequency and is dominated by the potassium component. We also show that recurrent synaptic transmission significantly modifies MC AHP and that the strength of the hyperpolarization produced by the AHP in the few milliseconds preceding the action potential (AP) emission determines MC firing frequency and AP timing. Moreover, we show that the AHP area is larger in younger animals, possibly owing to increased Ca 2+ influx during MC firing. Finally, we show that olfactory experience selectively reduces the early component of the MC AHP (under 25 msec), thus producing a modification of the AP timing limited to the higher firing frequency. On the basis of these results, we propose that the AHP, and its susceptibility to be selectively modulated by the recurrent synaptic transmission and olfactory experience, participate in odor coding and learning by modifying the frequency and pattern of MC firing. Abstract : The afterhyperpolarization (AHP) contribute to the neuronal coding by affecting the frequency and the pattering of neuronal firing. In the olfactory bulb the AHP of the mitral cells (MC) is composed by a potassium component and two synaptic, excitatory and inhibitory, components produced by the recurrent synaptic transmission. Here, we determine the relative contribution of the three components to the MC AHP and their impact on MC firing. We showed a predomination of potassium over synaptic components, that the three have a different temporal profile and are developmentally regulated.