Physiological mechanisms underlying calcium oscillations in olfactory bulb neurons
물리학과 비선형동역학 및 생물물리전공
Physiological mechanisms Calcium oscillations Olfactory bulb neurons;
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Though calcium signaling is related to various inter- and intra-cellular processes and shows complex behavior, the mechanisms generating calcium oscillation are very similar regardless of cell types. Olfactory bulb(OB) neurons often exhibit synchronized, spontaneous, intracellular calcium spikes, but their amplitude and frequencies are irregular while some type of cells such as hepatocytes, pituitary gonadotropes, and etc. show periodic oscillation. In our OB culture preparations, the majority of neuronal cell population showed irregular patterns of calcium spikes, and these spikes were highly synchronized in the region of close proximity with a good degree of network connectivity. The purpose of this thesis is to find the origin of irregular calcium spikes and of synchronization through experiments and computational model studies. We measured intracellular calcium level with a fluorescent imaging and electrical activities with a cell-attached patch clamp recording. Synchronized calcium spikes in OB neurons were driven by electrical bursts, for both calcium spikes and electrical activity disappeared by the application of TTX, while nifedipine, ω-CgTx, and ryanodine inhibited calcium activities leaving electrical bursts unaffected. Synchronization in OB cells was highly correlated in their electrical activities. Our finding suggests that synchronized calcium activity in OB neurons is initiated by synchronous electrical bursts. Since the existing calcium oscillation model could not reproduced the irregular calcium spikes observed in OB neurons, we made a new model. The new model incorporates the electrical activities to the calcium kinetics. The new model well reproduces the experimentally observed calcium spikes. We found that the activation and inactivation times of voltage operated calcium channels plays an important role in determining spike shapes.