Fig. 1. Effect of forskolin and IBMX pretreatments on GVBD and cAMP levels in Spisula oocytes. In (A) and (B), oocytes were pretreated with various combinations of forskolin and IBMX at indicated concentrations for 15 minutes before adding 5-HT (5 µM, A) or KCl (45 mM, B). DMSO, DMSO vehicle alone; Forsk/IBMX: Forskolin and IBMX (65/60 µM) without any activating agent. GVBD was scored after 20 minutes. Mean results (±s.e.m.) of four experiments are shown. In (C) and (D), the effect of incubating oocytes for one hour in the presence of forskolin (120 µM), IBMX (115 µM) or a combination of both (60/65 µM) on oocyte cAMP concentration (A) and on subsequent 5-HT-induced GVBD (B) is shown. Unt, oocytes left untreated; DMSO, oocytes treated with the DMSO vehicle alone (Panel C) and to which 5-HT was added (Panel D). Asterisk (*), significantly different from untreated oocytes. Mean results (±s.e.m.) of three experiments are shown.