Fig. 7. Effect of pretreatment of oocytes with SQ 22,536 on cAMP concentration and the time course of GVBD. (A) Oocytes were either pretreated with 1 mM SQ 22,536 (open symbols, ,) or left untreated (filled symbols, , ) for one hour prior to the addition of 5-HT (5 µM, , ) or KCl (45 mM, , ), at time 0. At indicated times, oocytes were fixed for determination of the percentage of GVBD. Mean results (±s.e.m.) of two experiments are shown. (B) Oocytes were divided in two lots, one to which SQ 22,536 (1 mM) was added () while the other was left untreated (). One hour later, 5-HT (5 µM) was added to an aliquot of both SQ 22,536-treated () and -untreated oocytes (). At indicated times, samples of oocytes were frozen and later processed for determinations of cAMP concentration expressed as a percentage of the initial cAMP concentration of oocytes at the beginning of the experiment. The inset depicts the corresponding time course of GVBD after addition of 5-HT, in both groups of oocytes. Mean results of two experiments are shown.