title: Axo-axonic GABA-immunopositive synapses on the primary afferent fibers in frogs.
abstract: In three frog species Rana esculenta, Rana temporaria and Xenopus laevis, the contacts established by gamma-aminobutyric acid and glutamate decarboxylase immunoreactive (-ir) terminals upon primary afferent fibers were studied using confocal and electron microscopy. For confocal microscopy, the primary afferent fibers were labeled through the dorsal root with Dextran-Texas Red, whereas gamma-aminobutyric acid and glutamate decarboxylase immunoreactivity were revealed with fluorescein isothiocyanate. Appositions of gamma-aminobutyric acid and glutamate decarboxylase immunoreactive profiles onto primary afferent fibers were observed and were considered as putative axo-axonic contacts of GABAergic terminals upon primary afferents. The latter was confirmed by the ultrastructural finding of axo-axonic synapses from gamma-aminobutyric acid immunopositive boutons upon the HRP-labeled primary afferent fibers in postembedding immunoelectron microscopic study. Such synapses may represent the morphological basis of GABAergic presynaptic inhibition of primary afferent fibers.
authors.affiliation: Sechenov Institute of Evolutionary Physiology and Biochemistry, Russian Academy of Sciences, St.-Petersburg, Russia.
authors.forename: N P
authors.initials: NP
authors.lastname: Vesselkin
authors.forename: V O
authors.initials: VO
authors.lastname: Adanina
authors.forename: J P
authors.initials: JP
authors.lastname: Rio
authors.forename: J
authors.initials: J
authors.lastname: Repérant
mesh_terms: D000818:Animals; D000906:Antibodies; D001369:Axons / Q000737:chemistry* / Q000201:enzymology / Q000648:ultrastructure; D005968:Glutamate Decarboxylase / Q000032:analysis / Q000276:immunology; D007150:Immunohistochemistry; D018613:Microscopy, Confocal; D016253:Microscopy, Immunoelectron; D009433:Neural Inhibition; D009475:Neurons, Afferent / Q000737:chemistry* / Q000201:enzymology / Q000648:ultrastructure; D011893:Rana esculenta; D011896:Rana temporaria; D013569:Synapses / Q000737:chemistry* / Q000648:ultrastructure; D014982:Xenopus laevis; D005680:gamma-Aminobutyric Acid / Q000032:analysis* / Q000276:immunology
chemical_list: D000906:Antibodies; D005680:gamma-Aminobutyric Acid; D005968:Glutamate Decarboxylase