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Effects of the GABA agonists baclofen and THIP on long-term compensation in hemilabyrinthectomised rats
Linköping University, Department of Biomedicine and Surgery, Cell biology. Linköping University, Faculty of Health Sciences.
Linköping University, Department of Neuroscience and Locomotion, Oto-Rhiono-Laryngology and Head & Neck Surgery. Linköping University, Faculty of Health Sciences.
Linköping University, Department of Neuroscience and Locomotion, Oto-Rhiono-Laryngology and Head & Neck Surgery. Linköping University, Faculty of Health Sciences.
1998 (English)In: Brain Research, ISSN 0006-8993, E-ISSN 1872-6240, Vol. 795, no 1-2, 307-311 p.Article in journal (Refereed) Published
Abstract [en]

Horizontal eye movements, elicited by sinusoidal rotation in darkness, were recorded with a magnetic search coil technique in pigmented rats, hemilabyrinthectomised 8–12 weeks before the investigation. Separate gains during rotation towards the lesioned side (LS) and the intact side (IS) were calculated by a computer program, demonstrating an asymmetry. Systemic single administration of the GABAB agonist baclofen caused a dose-related temporary rebalancing of the compensatory eye movements to the LS and the IS. At an optimal dose of 14 μmol/kg b.wt symmetry was achieved by excitation of eye movements during rotation to the LS and depression during rotation to the IS. Administration of the GABAA agonist THIP did not obviously reduce the asymmetry. It is suggested that stimulation of GABAB receptors modifies the tonic imbalance between the bilateral vestibular nuclei and/or the central processing of the input from the peripheral sensory organs.

Place, publisher, year, edition, pages
1998. Vol. 795, no 1-2, 307-311 p.
National Category
Medical and Health Sciences
Identifiers
URN: urn:nbn:se:liu:diva-84752DOI: 10.1016/S0006-8993(98)00329-1OAI: oai:DiVA.org:liu-84752DiVA: diva2:561518
Available from: 2012-10-19 Created: 2012-10-19 Last updated: 2017-12-07Bibliographically approved
In thesis
1. Central vestibular compensation: the role of the GABAB receptor
Open this publication in new window or tab >>Central vestibular compensation: the role of the GABAB receptor
2003 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The remarkable capacity for adaptive plastic changes in response to changed internal or external conditions is a distinctive feature of the vestibular system. Even in adults the system can be modified throughout life due to altered conditions caused by disease. trauma, medical treatment or normal ageing. Central nervous plastic changes following a unilateral peripheral vestibular loss are summarised by the term 'vestibular compensation'. This concept has become the most extensively investigated experimental model in studies of vestibular plasticity. The vestibular system governs a number of reflexes of which one is maintaining a stable gaze when the head moves - the vestibuloocular reflex. Since this reflex is relatively easy to quantify with non-invasive methods it constitutes an excellent tool for studying vestibular function in health and disease. Furthermore, the underlying neuronal circuitry of the reflex is phylogenetically ancient.

γ-Aminobutyric acid (GABA) is the most widely distributed inhibitory neurotransmitter in the vertebrate central nervous system. It acts via the classical GABAA and the more recently discovered GABAB receptors, the physiological functions of which are just beginning to emerge. The studies that provide the basis for this thesis systematically investigate the functional significance of the GABAB receptors for vestibular compensation during several stages after unilateral vestibular loss in rats. Firstly, the long-term maintenance of the partially normalised vestibular function weeks- months after the sensory loss was investigated (I and 11). Subsequently, the compensation that normalises the function of the vestibular system within a few days after the loss was investigated (III). Finally, in order to be able to investigate the acute stage, minutes - hours after unilateral vestibular loss, a method for reversible inactivation of the vestibular sensory input was developed (IV). In addition to information about the role of GABAB receptor function during this stage. the method also revealed the immediate behavioural consequences following a sudden transient vestibular loss as well as compensatory modulations that outlasted the inactivation of the sensory input (IV).

In summary, this thesis demonstrates a concrete physiological role of the GABAB receptors in a well-characterised neural system related to a specific behaviour. A direct causal relationship between the GABAB receptors and the physiological changes underlying compensation from a unilateral peripheral vestibular loss is established for all stages of the compensatory process. The physiological effect is partly mediated through an endogenous tonic control of the receptor. Furthermore, this thesis elucidates the immediate behavioural consequences of an acute transient loss of sensory vestibular input.

Place, publisher, year, edition, pages
Linköping: Linköpings universitet, 2003. 59 p.
Series
Linköping University Medical Dissertations, ISSN 0345-0082 ; 765
National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:liu:diva-25687 (URN)10063 (Local ID)91-7373-522-1 (ISBN)10063 (Archive number)10063 (OAI)
Public defence
2003-01-16, Berzeliussalen, Hälsouniversitetet, Linköping, 09:00 (Swedish)
Opponent
Available from: 2009-10-08 Created: 2009-10-08 Last updated: 2012-10-19Bibliographically approved

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Magnusson, Anna K.Eriksson, BirgittaTham, Richard

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