| Popis: |
The rat subcommissural organ (SCO), which forms the roof of the third ventricle is an adequate model to study certain mechanisms of neuron-glia interactions in vivo. The ependymocytes, the main component of the SCO, have a glial origin. They possess particular phenotypic characteristics: they accumulate [ 3 H]GABA by a specific uptake mechanism, contain transitory GFAP during ontogenesis and do not express PS100; on the other hand they receive a 5HT input which forms typical synaptic contacts. This innervation is of particular interest to approach neuron-glia interactions during the differentiation. Studies of GABA uptake carriers during ontogenesis in SCO ependymocytes show a correlation between the onset of the 5HT innervation and the advent of the GABA uptake. Moreover, destruction of the 5HT innervation by a neurotoxin (5-7-dihydroxytryptamine), before its arrival at the SCO in newborn rat, inhibits the formation of the GABA uptake system and causes the expression of PS100 in adult SCO cells. On the other hand, the SCO of newborn rats transplanted to the fourth ventricle of an adult host rat had no capacity to take up GABA and expressed PS 100 3 months after its transplantation. Finally, the SCO ependymocytes of species devoid of 5HT innervation (rabbit, mice) were unable to take up GABA and contain PS100. These data suggest that neuron-glia interactions are necessary for the advent of GABA uptake carriers and can control the expression of glial markers during ontogenesis in SCO ependymocytes. |
