Neuronal control of [3H]GABA uptake in the ependymocytes of the subcommissural organ: an in vivo model of neuron-glia interaction.
The rat subcommissural organ (SCO) is a particular but adequate paradigm for the approach, in vivo, to some aspects of neuron-glia interaction in gamma-aminobutyric acid (GABA) uptake. The rat SCO ependymocytes (the main component of this structure lying at the junction of the aqueduct and the third ventricle) accumulate [3H]GABA by a highly specific uptake mechanism and receive a serotoninergic input forming typical synaptic contacts. It seems that there is a correlation between the capacity of the rat SCO ependymocytes to take up [3H]GABA and the presence of a serotonin (5-HT) innervation. Indeed, in the newborn rat, no uptake of [3H]GABA was observed before the onset of this innervation and the increased [3H]GABA accumulation in the SCO was correlated with the appearance of the 5-HT terminals in the SCO. Moreover, in the mouse, whose SCO is devoid of a 5-HT innervation, no accumulation of [3H]GABA was observed in the SCO ependymocytes. Thus, the 5-HT innervation could be involved directly or indirectly in the onset of the GABA uptake carriers. On the other hand, in adult rats parachlorophenylalanine (pCPA) treatment decreased the 5-HT content of the SCO, and increased [3H]GABA accumulation; such an augmentation was not observed when rats were treated with pCPA plus 5-hydroxytryptophan to restore the 5-HT content. However, an increase in 5-HT content of the SCO by pargyline treatment appeared to have no effect on [3H]GABA uptake. Control of GABA uptake activity by 5-HT in the SCO ependymocytes could be an interesting model for the study of a possible interaction between amino-acids and other neurotransmitters by terminating their action in the extracellular space.
Didier-Bazes
M
M
INSERM U171-CNRS UA 1195, Centre Hospitalier Lyon-Sud, Pierre Benite, France.
Aguera
M
M
Chouaf
L
L
Harandi
M
M
Calas
A
A
Meiniel
A
A
Belin
M F
MF
D000818:Animals; D004805:Ependyma / Q000378:metabolism*; D010134:Fenclonine / Q000494:pharmacology; D008297:Male; D009457:Neuroglia / Q000378:metabolism*; D009474:Neurons / Q000378:metabolism*; D009490:Neurosecretory Systems / Q000378:metabolism*; D010293:Pargyline / Q000494:pharmacology; D051381:Rats; D012701:Serotonin / Q000378:metabolism / Q000502:physiology*; D013351:Subcommissural Organ / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D005680:gamma-Aminobutyric Acid / Q000493:pharmacokinetics*
D012701:Serotonin; D005680:gamma-Aminobutyric Acid; D010293:Pargyline; D010134:Fenclonine