Differential distribution of GABA- and serotonin-containing afferents on an identified central neuron.
The distributions of gamma-aminobutyric acid (GABA)- and serotonin (5-HT)-containing terminals impinging on the surface of the Mauthner (M-) cell were studied at the light microscopic level using double immunofluorescent labeling and were compared with that of the glycine receptor. The latter was visualized indirectly, using a monoclonal mouse antibody which recognizes its 93-kDa associated protein. This neuron has two large principal dendrites: one extending ventrorostrally (ventral dendrite) and the other dorsolaterally (lateral dendrite). There are also two other classes of smaller processes: one that projects ventrally (small ventral dendrites) and one penetrating in the axon cap (cap dendrites), a peculiar neuropil surrounding the initial segment of the M-cell axon. A cellular regionalization of these afferent systems was found: GABA boutons, labeled for glutamic acid decarboxylase (GAD), were localized preferentially on the lateral dendrite while 5-HT-filled endings predominated on the ventral one. The density of these two classes of inputs was comparable in the other areas of the M-cell: less of their terminals were in contact with the soma outside the axon cap, and more numerous boutons, which presented either GABA or 5-HT immunoreactivities, were apposed to the small ventral dendrites. This preferential pattern of innervation differed with the ubiquitous presence of glycine receptor clusters on the M-cell membrane. Finally no evidence of a colocalization of GABA and 5-HT in afferent endings was detected at any portion of the M-cell.(ABSTRACT TRUNCATED AT 250 WORDS)
Petrov
T
T
Laboratoire de Neurobiologie Cellulaire (I.N.S.E.R.M. U261), Institut Pasteur, Paris, France.
Seitanidou
T
T
Triller
A
A
Korn
H
H
D000818:Animals; D005455:Fluorescent Antibody Technique; D005968:Glutamate Decarboxylase / Q000276:immunology; D005998:Glycine / Q000502:physiology; D006054:Goldfish / Q000502:physiology*; D009411:Nerve Endings / Q000502:physiology; D009412:Nerve Fibers / Q000502:physiology; D009474:Neurons / Q000502:physiology*; D009475:Neurons, Afferent / Q000502:physiology*; D012701:Serotonin / Q000502:physiology*; D013194:Staining and Labeling; D005680:gamma-Aminobutyric Acid / Q000502:physiology*
D012701:Serotonin; D005680:gamma-Aminobutyric Acid; D005968:Glutamate Decarboxylase; D005998:Glycine