GABA- and glycine-like immunoreactivity in axonal endings presynaptic to the vibrissa afferents in the cat trigeminal interpolar nucleus

• Published in: Neuroscience Vol. 152; no. 1; pp. 138 - 145
• Main Authors: Moon, Y.S, Paik, S.K, Seo, J.H, Yi, H.W, Cho, Y.S, Moritani, M, Yoshida, A, Ahn, D.K, Kim, Y.S, Bae, Y.C
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 03.03.2008; Elsevier
• Subjects: Animals; axoaxonic synapse; Biological and medical sciences; Cats; Fundamental and applied biological sciences. Psychology; gamma-Aminobutyric Acid - metabolism; Glycine - metabolism; Immunohistochemistry; Microscopy, Electron, Transmission; Neurology; Neurons, Afferent - metabolism; Neurons, Afferent - ultrastructure; presynaptic inhibition; Presynaptic Terminals - metabolism; Presynaptic Terminals - ultrastructure; trigeminal; Trigeminal Nuclei - metabolism; Trigeminal Nuclei - ultrastructure; ultrastructure; Vertebrates: nervous system and sense organs; Vibrissae - innervation; trigeminal sensory nuclei; HRP; primary afferent depolarization; phosphate buffer; p-endings; trigeminal principal nucleus; axoaxonic synapse; VPM; Vi; primary afferent terminals; horseradish peroxidase; trigeminal oral nucleus; Vo; Vp; immunohistochemistry; trigeminal; 3,3′-diaminobenzidine tetrahydrochloride; presynaptic inhibition; DAB; TBST; trigeminal interpolar nucleus; ultrastructure; TSN; ventral posteromedial nucleus of thalamus; Tris-buffered saline containing 0.1% Triton X-100; PAD; PB; PATs; pleomorphic vesicle-containing presynaptic endings; Immunohistochemistry; Fissipedia; Carnivora; Central nervous system; Presynaptic inhibition; Glycine; Encephalon; Vertebrata; Axoaxonic synapse; Mammalia; Ultrastructure; Animal; Cat; Neurotransmitter; GABA; Trigeminal nucleus; Vibrissa
• ISSN: 0306-4522; 1873-7544
• DOI: 10.1016/j.neuroscience.2007.11.033

Abstract The goal of this study was to analyze the synaptic interaction of primary afferents with GABA- and/or glycine-immunopositive presynaptic endings in the cat trigeminal interpolar nucleus (Vi). Fast adapting vibrissa afferents were labeled by intra-axonal injections of horseradish peroxidase. Postembedding immunogold labeling on serially cut ultrathin sections and quantitative ultrastructural analysis of the labeled boutons and their presynaptic endings (p-endings) in the Vi were performed. The majority of p-endings presynaptic to labeled boutons (83%) were immunopositive for both GABA and glycine and 8% were immunopositive for glycine alone. A small fraction of p-endings were immunopositive for GABA alone (4%) or immunonegative for both GABA and glycine (4%). Ultrastructural parameters related to synaptic release, i.e. bouton volume, mitochondrial volume, and active zone area, were significantly larger in the labeled boutons of primary afferents than in the p-endings. The volume of labeled boutons was positively correlated with the number of the postsynaptic dendrites and p-endings. In addition, fairly large-sized labeled boutons and p-endings were frequently observed in the Vi. These results reveal that large majority of vibrissa afferents in the Vi are presynaptically modulated by interneurons immunopositive for both GABA and glycine, and suggest that the Vi plays a distinct role in the processing of orofacial sensory information, different from that of other trigeminal sensory nuclei.