I. Reichenberger et N. Dieringer, SIZE-RELATED COLOCALIZATION OF GLYCINE AND GLUTAMATE IMMUNOREACTIVITYIN FROG AND RAT VESTIBULAR AFFERENTS, Journal of comparative neurology, 349(4), 1994, pp. 603-614
Presence and distribution of glutamate, glycine, GABA and beta-alanine
in VIIIth nerves of frogs and rats were investigated with postembeddi
ng immunocytochemical methods on serial. In Scarpa's ganglion of the f
rog, all cell bodies were glutamate immunoreactive. About 17% semithin
sections. of the cells per section were also glycine immunoreactive,
but none were GABA or p-alanine immunoreactive The mean diameter of gl
ycine-positive cell bodies (26.7 +/- 6.9 mu m; N = 130) was significan
tly (P < 0.0001) larger than that of glycine-negative cell bodies (15.
7 +/- 5.4 mu m; N = 272). The intensity of glutamate immunostaining de
creased with cell diameter, whereas the intensity of glycine immunosta
ining increased with cell diameter. As a result, the staining intensit
ies for glutamate and glycine in a given cell were negatively correlat
ed. Glycine immunoreactivity was also present in a size-related manner
in distal and proximal afferent fibers. The majority of thin fibers (
<4 mu m) was glycine negative, whereas most of the thick fibers (>10 m
u m) were glycine positive. Glycine-positive fibers were observed in t
he sensory epithelia of ail end organs in the inner ear. The saccular
macula and its nerve, however, contained only few glycine-immunoreacti
ve structures. In Scarpa's ganglion of the rat, all cells were immunor
eactive for glutamate, about 12% for colocalized glycine, and none for
GABA or beta-alanine Glycine-positive cell bodies were significantly
(P < 0.0001) larger (32.2 +/- 5.2 mu m; N = 82) than glycine-negative
cell bodies (25.1 +/- 5.3 mu m; N = 274). Cell bodies in the spiral ga
nglion were only glutamate immunoreactive, whereas staining for glutam
ate, glycine, and GABA was dense in the ventral cochlear. These result
s demonstrate that thicker vestibular afferent fibers represent a part
icular subpopulation that differs from the majority of thinner afferen
ts due to their glycine immunoreactivity. (C) 1994 Wiley-Liss, Inc.