Neurons modulate oxytocin receptor expression in rat cultured astrocytes:: Involvement of TGF-β and membrane components

We examined the effect of neurons on oxytocin (OT) receptors (OTR) and OTR gene expression in cultured astrocytes. The addition of neuron-conditioned medium induced an increase of both OTR binding and OTR mRNA level. This effect was enhanced after the medium was boiled or acidified. As it is known that transforming growth factor-beta (TGF-beta) can be released from carrier proteins by acid or heat, TGF-beta1 and 2 were tested and found to induce an increase of OTR binding. Furthermore, TGF-beta antibody abolished the stimulatory effect of normal or acidified neuron-conditioned medium. Neurons added to cultured astrocytes without contact mimicked the stimulatory effect of the conditioned medium. In contrast, neurons added with contact, induced a decrease in OTR binding and an increase of mRNA level, whereas neuronal membranes induced a decrease of both OTR binding and mRNA levels. In conclusion, the present data demonstrate that in vitro, neurons are able to modulate astrocytic OTR expression at the level of both protein and mRNA. They stimulate this expression through their release of TGF-beta and inhibit it by the action of unknown membrane components. (C) 2002 Wiley-Liss, Inc.