Role Of Hyperpolarization Activated Mixed Cationic Current In Electrophysiological Properties Of Medial Vestibular Nucleus Neuron

Objective:To study how hyperpolarization activated mixed cationic current (IH) effects on intrinsic membrane properties of medial vestibular nucleus (MVN) neurons. To discuss the potential role of IH plays in signal transmission. Methods:Using infrared differential interference contract technique, to record the firing of MVN neurons. Record MVN neuron firing curves, under the condition of resting potential and analog input current, separately. After that, add ZD7288(50μM) to block IH. Repeat previous record5minutes later and analyze how the intrinsic membrane potential shifts without IH. Results:1. Using current clamp mode, we find most MVN neurons show unique "depolarizing voltage sag" which can be blocked by ZD7288.2. Spontaneous firing rate and resting potential of MVN neuron have no significant change after using ZD7288.3. With hyperpolarized current injected, after blocking IH the membrane potential become more negative while input resistance increases.4. Injecting hyperpolarized ramp current, the first spike is delayed, threshold of first spike is more positive, and the initial frequency is increased without IH. Conclusion:1.IH exists on most MVN neurons.2. IH is not required for spontaneous spiking in MVN neurons.3. IH contributes to Integrative Properties of MVN neurons and accuracy of input-output signaling at subthreshold potentials. Objective:To study how hyperpolarization activated mixed cationic current (IH) effects on neural integration of medial vestibular nucleus (MVN) neurons. Methods:By using infrared differential interference contract technique, MVN neurons were recorded with current clamp mode. In this research, the VIII brain nerve was stimulated in order to induce excitatory postsynaptic potential (EPSPs) and inhibitory postsynaptic potential (IPSPs). Record the EPSPs and IPSPs before and after adding IH blocker ZD7288(50μM), Compare the amplitude and half width of postsynaptic potential. Result:1.After blocking IH, the time course of postsynaptic potential extends significantly. IH constrains the temporal summation of MVN neurons.2. After blocking IH, the amplitude of postsynaptic potential increases. IH constrains the spatial summation of MVN neurons. Conclusion: Hyperpolarization activated mixed cationic current plays an important role in dendrites integration of medial vestibular nucleus neurons. IH enhances the accuracy of dendrites integration, and reduces the sensibility of MVN neurons to tiny local stimulation.