EFFECTS OF ARGININE-VASOPRESSIN AND ATRIOPEPTIN ON CHLORIDE UPTAKE INCULTURED ASTROGLIA

Ion and water homeostasis in the CNS is subjected to a neuroendocrine control exerted by neuropeptides formed within the brain. In order to gain information on this neuroendocrine control of Cl- homeostasis, Cl -36(-) uptake was measured in cultured Type-I astrocytes exposed to th e neuropeptides [Arg8]Vasopressin (AVP), and atriopeptin (AP) and to v arious Cl- transport modifiers. AVP increased while AP decreased Cl-36 (-) uptake of cultured astrocytes in a dose-dependent manner. Both eff ects became statistically significant at greater than 10(-9) M concent ration of the peptides. For the appearance of the effects at least 30- min exposure was necessary. AVP and AP extinguished each other's effec t by almost stochiometric manner. When administered together with AVP, the V1A vasopressin receptor antagonist ''Manning compound'' inhibite d, while V2 vasopressin receptor agonist did not influence the Cl-36(- ) uptake-increasing effect of AVP. However, bumetanide, a specific inh ibitor of Na+-K+-2Cl(-) cotransport, inhibited the effect of vasopress in and also inhibited the Cl-36(-) uptake of AVP non-treated, control cells. Our findings suggest that brain Cl- homeostasis is controlled b y neuroendocrine system in the CNS.