Cell swelling induces exocytosis of material stored in secretory vesicles. We have shown that swelling-induced secretion possesses limited selectivity; hypotonic medium evokes TRH but not oxytocin (OT) release from hypothalamic paraventricular nucleus (PVN) and neurohypophysis (NH). It was the aim of present study to ascertain whether the swelling-induced oxytocin secretion could be unmasked by the inhibition of specific osmotic response using Ca2+ free medium and GdCl3, an inhibitor of stretch activated channels. OT release from PVN was stimulated by the hypotonic medium only in presence of either 50 or 100 mM of GdCl3. OT release from supraoptic nucleus (SON) was also stimulated by the Ca2+ free hypotonic medium in presence of GdCl3. OT secretion from NH was not stimulated even in presence of GdCl3 either in Ca2+ containing or Ca2+ free medium. TRH response to swelling inducing stimulus was not affected by GdCl3. Intranuclear OT secretion in response to hyposmotic stimulation in PVN and SON could be unmasked by the inhibiting specific response by GdCl3. At this conditions general secretory response to swelling-inducing stimuli emerged. Secretion of OT from NH was not affected by any of these treatments Acknowledgements: Supported by 23191/23 of the Grant Agency VEGA.