J Korean Bal Soc.
2003 Jun;2(1):78-85.
Ionic mechanisms underlying spontaneous firing in isolated type B medial vestibular nucleus neurons
- Affiliations
-
- 1Department of Physiology, Wonkwang University School of Dentistry, and Wonkwang Dental Research Institute, Vestibulocochlear Research Center at Wonkwang University, Iksan 570-749, Korea. byungp@wonkwang.ac.kr
Abstract
- Medial vestibular nucleus (MVN) neurons are found to have spontaneous electrical activity in the absence of any detectable synaptic input. To investigate the contributions of intrinsic mechanisms to the spontaneous activity of type B MVN neurons, we examined the effects of various channel blockers on spontaneous firing by means of patch clamp recordings. Coronal slice (400 micrometer) of the vestibular nucleus region was sequentially treated with pronase 0.2 mg/ml and thermolysin 0.2 mg/ml, then single neurons were mechanically dissociated. MVN neurons recorded in neonatal rat were shown to have either a single deep afterhyperpolarization (AHP; type A cells), or an early fast and a delayed slow AHP (type B cells). In 300 nM TTX, spontaneous firing was blocked in type B cells tested. In 8 of 11 cells, underlying fluctuation or oscillations in membrane potential was not remained, and hyperpolarization did not produce rebound low-threshold calcium spikes. Although type B MVN neurons possessed hyperpolarization activated cation current (Ih), cesium had no effect on firing rates. The spike AHP is calcium dependent. When Ca2+ influx was blocked in external Ca2+ free solution, repetitive firing was abolished and the cell rested at depolarized membrane potentials. Application of apamin (300 nM) caused a profound reduction in the amplitude of the AHP and produced rhythmic burst firing. These findings suggest that the spontaneous activity of type B MVN neurons is regulated by interactions between the membrane depolarization mainly due to a persistent sodium conductances and hyperpolarization due to the calcium-activated potassium conductances.
- Full Text Links
-
- Actions
-
Cited
- CITED
-
- Close
- Share
-
- Similar articles
-
- Effects of Norepinephrine on the Resting Activity of Medial Vestibular Nuclear Neurons in the Rat
- Modulation of the Neuronal Activity of Vestibular Nuclear Neurons by 8-OH-DPAT
- Changes in Excitability of Neurons in Rat Medial Vestibular Nucleus Following Vestibular Neurectomy
- Roles of Ca2+ activated K+ conductances on spontaneous firing patterns of isolated rat medial vestibular nucleus neurons
- Application of Tetrode Technology for Analysis of Changes in Neural Excitability of Medial Vestibular Nucleus by Acute Arterial Hypotension
