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Excitatory amino acid receptors in normal and abnormal vestibular function
P F Smith1, C de Waele, P P Vidal
1Department of Psychology, Dunedin, New Zealand.
Molecular Neurobiology
|January 1, 1991
Summary
Excitatory amino acid receptors in the brainstem are crucial for vestibular reflexes. N-methyl-D-aspartate (NMDA) receptor antagonists impair vestibular compensation, suggesting their role in plasticity.
Area of Science:
- Neuroscience
- Vestibular System Research
- Receptor Pharmacology
Background:
- Excitatory amino acid (EAA) receptors are well-studied in the limbic system and neocortex, but their function in the brainstem, particularly the vestibular nucleus (VN), is less understood.
- Biochemical and electrophysiological studies indicate that synapses in the VN utilize EAAs, primarily acting on kainate or alpha-amino-3-hydroxy-5-methyl-4-isoxazole-propionic acid (AMPA) receptors for ipsilateral vestibular input.
- Electrophysiological evidence also suggests N-methyl-D-aspartate (NMDA) receptors mediate part of the contralateral vestibular input and spinal cord input to the VN.
Purpose of the Study:
- To investigate the role of excitatory amino acid (EAA) receptors in brainstem vestibular pathways.
- To explore the involvement of different EAA receptor subtypes (kainate, AMPA, NMDA) in vestibular nucleus (VN) function.
- To examine the impact of NMDA receptor activity on vestibular compensation and plasticity.
Main Methods:
- Review of existing biochemical and electrophysiological studies on EAA receptors in the brainstem vestibular system.
- Analysis of in vitro electrophysiological data from vestibular nucleus preparations.
- Examination of studies investigating the effects of NMDA receptor antagonists on vestibular compensation following deafferentation.
Main Results:
- EAA receptors, including kainate, AMPA, and NMDA subtypes, are implicated in vestibular reflex pathways within the brainstem.
- While in vitro studies suggest specific receptor roles, potential artifacts from denervation in explant preparations must be considered.
- NMDA receptor antagonists have been shown to disrupt behavioral recovery (vestibular compensation) after unilateral vestibular deafferentation.
Conclusions:
- EAA receptors play a significant role in various vestibular reflex pathways in the brainstem.
- Vestibular compensation may involve NMDA receptors, with a hypothesis suggesting their upregulation or increased affinity in the deafferented VN, though direct evidence is currently lacking.
- Further research is needed to fully elucidate the precise mechanisms and roles of EAA receptors in vestibular plasticity and function.