Expression of Glycine Receptors by Identified Alpha and Gamma Motoneurones
The neurotransmitter role of glycine is well established and has recently been reviewed by Aprison (1990). Glycine is a major inhibitory neurotransmitter in the mammalian spinal cord, and it exerts its postsynaptic effects via increases in the chloride permeability of the postsynaptic membrane. Glycine receptors, like GABAA receptors, are multimeric ligand-gated chloride channels whose structural and functional properties have been elucidated in great detail in recent years (Betz, 1991). Glycine receptor subunit mRNAs are expressed in widespread areas of the central nervous system (CNS; e.g. Malosio, Marquèze, Kuhse & Betz, 1991; Kirsch, Malosio, Wolters & Betz, 1993a). Advances in understanding of the molecular composition of glycine receptors have also led to the use of monoclonal antibodies against subunits of the glycine receptor complex (Pfeiffer, Simler, Grenningloh & Betz, 1984) to study the general localisation of glycine receptors in the CNS (e.g. Triller, Cluzead, Pfeiffer, Betz & Korn, 1985; Triller, Cluzead & Korn 1987; van den Pol & Gorcs, 1988). One of the antibodies used for such immuno-localisation studies is directed against gephyrin, a 93 kDa glycine receptor-associated, tubulin binding protein which is required for glycine receptor clustering and localisation at synaptic specialisations (Kirsch, Wolters, Triller & Betz, 1993b). In the mammalian ventral horn, gephyrin immunoreactivity has been shown to be localised to the sub-membrane cytoplasm, coincident with immunoreactivity against ligand binding subunits of the glycine receptor, and, importantly, is localised at sites corresponding to synaptic specialisations (see Triller et al., 1985 and unpublished observations from our laboratory). These properties make gephyrin a particularly useful marker for use in probing the organisation and distribution of glycine receptors in identified central neurones, as we will describe in this presentation.
KeywordsGlycine Receptor Recurrent Inhibition Size Gradient Synaptic Specialisation Presynaptic Active Zone
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