Strychnine-sensitive glycine receptors in rat caudatoputamen are expressedby cholinergic interneurons

Strychnine-sensitive glycine receptors are ligand-gated anion channels wide ly expressed in spinal cord and brainstem. Recent functional studies demons trating glycine-induced release of [H-3]acetylcholine in rat caudatoputamen suggested the existence of excitatory glycine receptors in that region. Si nce the expression of glycine receptors in the caudatoputamen had not been reported earlier, we studied the glycine receptor-like immunoreactivity in this structure using a monoclonal antibody (mAb4a) recognizing an epitope c ommon to all of the ligand-binding alpha-subunit variants of the glycine re ceptor. [Becker ed al. (1993) Brain Res. 11, 327-333; Nicola et al. (1992) Neurosci. Lett. 138, 173-178]. Immunohistochemistry with mAb4a disclosed a specific staining of sparsely distributed large neurons in rat caudatoputam en, displaying an immunoreactive signal of lower intensity than that observ ed in motoneurons in spinal cord. Fluorescent dual labelling demonstrated t hat glycine receptor-like immunoreactivity co-localizes with choline acetyl transferase-like immunoreactivity in rat caudatoputamen. All neurons with g lycine receptor-like immunoreactivity in the caudatoputamen studied were im munoreactive with choline acetyltransferase, and represented a subpopulatio n of cholinergic neurons (approximately 90% of the somata with choline acet yltransferase-like immunoreactivity). These results suggest that strychnine-sensitive glycine receptors are prese nt on cholinergic interneurons in rat caudatoputamen, supporting the hypoth esis that glycine receptors inducing striatal release of [H-3]acetylcholine may be localized to cholinergic neurons. (C) 2000 IBRO. Published by Elsev ier Science Ltd.