Glycine, glycine receptor subunit and glycine transporters in the rat parabrachial and Kolliker-Fuse nuclei

In the present study, we investigated the expression and distribution of ke y molecules in the parabrachial (PB) and Kolliker-Fuse nuclei (KF) that det ermine glycinergic signal transduction. By means of immunocytochemistry, we analyzed the amino acid glycine (Gly), the glycine transporters 1 and 2 (G lyT1, GlyT2), and the ligand binding glycine receptor-subunit al (GlyR alph a 1). Gly-immunoreactivity (-ir) was mainly found in varicose fibers and pr esumed terminal boutons; Gly-ir cell bodies were only occasionally seen. Im munoreactivity for GlyT2 was located in axons while GlyT1-staining was diff use in the neuropil. Immunolabeling for GlyR alpha 1 occurred mostly as gra nular staining diffusely distributed throughout the neuropil. Only in the s uperior lateral PB, the lateral crescent of the PB, and caudally in the KF did GlyR alpha 1-ir outline cell bodies and primary and higher-order dendri tes. Furthermore, our data demonstrate a distinct codistribution of immunor eactivities for Gly, ClyT2, and GlyR alpha 1 in a specific set of PB nuclei and in the KF. Strong staining was consistently seen in the internal later al PB, the ventral lateral PB, the lateral crescent, the medial PB adjacent to the superior cerebellar peduncle, and the rostral two-thirds of the KF Moderate to weak immunostaining was present in the superior, central, and d orsal lateral PBI the external medial PB, the medioventral part of the medi al PB, and caudally in the KF In contrast, remaining nuclei such as the ext ernal lateral PB and the waist area were essentially devoid of Gly-ir profi les, GlyT2-ir, and GlyR alpha 1-ir. Immunoreactivity for GlyT1 was evenly d istributed throughout all nuclei of the medial and lateral PB, including th e external lateral PB and the waist area, while the KF was only weakly stai ned. Our data provide evidence that glycinergic mechanisms might play a rol e for neural processing in most nuclei of the PB and in the KF. Only the ex ternal lateral PB and the waist area are apparently not subject to glyciner gic inhibition.