Inhibitory glycine receptors are most abundant in spinal cord and brainstem, and glycinergic synapses have a well-established role in the regulation of locomotor behavior. Little is known about the function of glycine receptors in cortex and hippocampus, where GABA plays a dominant role in synaptic inhibition. Therefore, we have investigated tissue and cellular expression of glycine receptor alpha-subunits. Western blot and immunohistochemical analyses reveal the presence of glycine receptors in hippocampal tissue. Immunocytochemical experiments in hippocampal cultures show prominent cellular expression of glycine receptors in pyramidal neurons and GAD-positive interneurons similar to the calcium-binding protein VILIP-I with widespread hippocampal distribution. On the subcellular level we found co-staining of GlyR and the presynaptic marker synapsin 1. Furthermore, co-staining with GAD at synaptic terminals indicated partial co-localization of GABA- and glycine receptors. (C) 2004 Elsevier Inc. All rights reserved.