Fig. 6. Effects of isobutylmethylxanthine (IBMX) on the cyclic adenosine 3′,5′-monophosphate (cyclic AMP) efflux. In the presence of 200 μm IBMX, cells were treated with 100 μm diazepam or 100 μm midazolam, and stimulated with 1 μm corticotropin-releasing hormone (CRH) or 10 μm forskolin. The ratios of cyclic AMP efflux to that of nonstimulated controls are expressed as means ± SD from four experiments. *P < 0.05 versus  cells stimulated with CRH without benzodiazepines and IBMX. #P < 0.05 versus  cells stimulated with forskolin without benzodiazepines and IBMX. §P < 0.05 versus  nonstimulated controls. ‡P < 0.05 versus  cells stimulated by each secretagogue without benzodiazepines in the presence of IBMX.