Serotonin and serotoninergic neurons. A radioautographic and immunocytochemical study of the nucleus raphe dorsalis and nucleus dorsomedialis hypothalami.
In an attempt to define cytophysiological criteria with which to establish whether or not a given neuron is serotoninergic, radioautography was combined with serotonin (5-HT) immunocytochemistry on the same sections from the nucleus raphe dorsalis (NRD) and/or nucleus dorsomedialis hypothalami (NDM) in rats subjected to intraventricular administrations of (3H)-5-HT or (3H)-dopamine (DA). All the (3H)-5-HT-accumulating neurons (cell bodies, dendrites and terminals) were found to be distinct from the (3H)-DA labeled ones and invariably immunostained for 5-HT in both regions studied. However, some immunoreactive neuronal elements within the area of tracer diffusion did not exhibit significant radioautographic labeling. In the NDM where 5-HT immunoreactive nerve cells could be detected only after intraventricular administration of 5-HT, these were found to be definitely distinct from the tyrosine hydroxylase immunoreactive and (3H)-DA labeled neurons of the dopaminergic periventricular-arcuate complex. After immunostaining for GAD at the electron microscopic level, (3H)-5-HT labeled nerve cells and terminals were not found to exhibit any significant immunoreactivity. Associations between (3H)-DA labeled and GAD immunoreactive processes with 5-HT immunoreactive or (3H)-5-HT-accumulating neurons, respectively, could also be observed in the NDM. When considered as a whole along with previous observations by other authors indicating a probable synthesis of 5-HT within NDM neurons, our data suggest that a given neuron can be classified as serotoninergic on the sole basis of its ability to selectively take up exogenous 5-HT under experimental conditions compatible with non interspecific labeling of catecholaminergic neurons. They also provide valuable information on the neurochemical environment and possible control of central serotoninergic neurons.
Arezki
F
F
Laboratoire de Neurobiologie, CNRS, Marseille, France.
Afailal
I
I
Bosler
O
O
Steinbusch
H W
HW
Calas
A
A
D000818:Animals; D004298:Dopamine / Q000032:analysis / Q000493:pharmacokinetics; D004302:Dorsomedial Hypothalamic Nucleus / Q000032:analysis / Q000648:ultrastructure*; D005968:Glutamate Decarboxylase / Q000032:analysis; D007033:Hypothalamus, Middle / Q000648:ultrastructure*; D007150:Immunohistochemistry; D008297:Male; D009474:Neurons / Q000032:analysis / Q000648:ultrastructure; D011903:Raphe Nuclei / Q000032:analysis / Q000648:ultrastructure*; D051381:Rats; D011919:Rats, Inbred Strains; D012701:Serotonin / Q000032:analysis* / Q000276:immunology / Q000493:pharmacokinetics; D014446:Tyrosine 3-Monooxygenase / Q000032:analysis
D012701:Serotonin; D014446:Tyrosine 3-Monooxygenase; D005968:Glutamate Decarboxylase; D004298:Dopamine