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Title: An electrophysiological study of medial vestibular nucleus neurones in vitro
Author: Johnston, Alexander R.
Awarding Body: University of Edinburgh
Current Institution: University of Edinburgh
Date of Award: 1996
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This thesis describes experiments on a horizontal slice of the dorsal brainstem containing the medial vestibular nuclei (MVN) from the mouse and rat, in which the electrophysiological characteristics of the spontaneously active neurones of the immature and adult MVN were studied. The results show that there are two electrophysiologically distinct cell types in the MVN, type A cells and type B cells. Type A cells are characterised by a single deep afterhyperpolarisation (AHP) following their spontaneous action potential. Type B cells on the other hand, are characterised by a fast transient AHP which is followed by a second slower AHP. It was demonstrated using intracellular recording techniques that type A cells comprised 33% of the total cells sampled in the rat MVH, in contrast type B cells comprised 67%. Type A cells fired at a higher mean frequency than type B cells. With the use of selective antagonists to block voltage-gated potassium and calcium channels and calcium-substituted media, it was shown that the ionic conductances involved in spike repolarisation and the AHPs of the two cell types are different. In type A cells, TEA increased spike duration and reduced the single deep AHP. A further increase in spike duration was observed in calcium-free medium containing TEA and the AHP was abolished. Apamin had little effect on the action potential shape of type A cells. In contrast, the spontaneous action potentials of type B cells developed plateau potentials in TEA. The fast AHP of type B cells was unaffected by apamin whereas the slow AHP was abolished. Thus, it was concluded that a in type A cells spike repolarisation and the deep single AHP involve a TEA-sensitive potassium current (Ik) and an apamin-insensitive calcium-activated potassium current, (Ic), while in type B cells the apamin-sensitive calcium-activated potassium current IAHP is responsible for the slow AHP.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available