The arginine vasopressin (AW) released from the hypothalamic slices containing paraventricular and supraoptic nuclei of Sprague-Dawley rats sectioned with vibratome and incubated in static microchambers was measured by radioimmunoassay. The effect of bovine serum albumin-conjugated corticosterone (B-BSA) on the AVP release was investigated. The results were as follows: (1) B-BSA, within 20 min, significantly inhibited AVP release in a dose-dependent manner from 10(-7) to 10(-4) mol/l. (2) RU38486 (10(-4)-10(-3) mol/l) could partially block the inhibitory effect of B-BSA although it by itself did not change the AVP release. (3) With the elevation of Ca2+ concentration in the incubation medium, the AVP release was increased and the inhibitory effect of B-BSA enhanced; while in the absence of Ca2+, the AVP release decreased and the effect of B-BSA attenuated. (4) The inhibitory effect of B-BSA was enhanced in the presence of neomycin which itself had no influence on AVP release. These results indicated that the inhibitory effect of corticosterone is rapid and membrane-mediated which is non-genomic rather than classical genomic, and that the extracellular Ca2+ play a role in this rapid inhibitory effect.