Myometrial contractions in vitro can be inhibited by transient [cAMP] elevation. 48 h exposure to iloprost has been reported to enhance oxytocin-induced contractions in human tissue via increased [cAMP] and PKA activity (1). We have shown cAMP agonists enhance COX-2 expression in human myometrial cells via MAPK signalling cascade (2). The impact of prolonged exposure to cAMP agonists on human myometrial tissue spontaneous contractility has not been demonstrated, despite growing interest in the use of [cAMP]-elevating therapies to prevent preterm labour. In the present study, human myometrial tissue samples were obtained (informed written consent) from women undergoing caesarean section (37-42 weeks, non-labour, TNL; n=88). Tissue strips were incubated in serum-free DMEM, under tension (5.9-7.9 mN) for 24 and 48 h with rolipram, forskolin, 8-bromo-cAMP, dibutyryl cAMP, 6-Bnz-cAMP and iloprost, plus vehicle controls (DMSO or H2O). Contractile activity was subsequently measured using an isometric organ bath. Mean integral tension (mean ± SEM) and related contraction parameters were analysed. Acute (1 h) exposure of myometrial tissue to cAMP agonists was also assessed. Statistical significance was tested using a Wilcoxon test. Our experiments showed that pre-treatment (24 h) with 1 mM 8-bromo-cAMP, 1 μM rolipram or 10 µM rolipram resulted in 5.2, 3.4, and 2.8 -fold greater spontaneous contractile activity than vehicle control, respectively (P<0.05) (n=6). Pre-treatment (48 h) with 1 mM 8-bromo-cAMP or 1 μM forskolin also resulted in increased spontaneous contractile activity (19.1-fold and 3.7-fold respectively) versus vehicle control (P<0.05) (n=6). Oxytocin-induced contractions were enhanced following pre-treatment (24 h) with 1 mM dibutyryl cAMP (1.3-fold versus vehicle control, P<0.05) (n=6). In conclusion, long-term [cAMP] elevation can increase the ability of myometrial tissue to spontaneously contract, as demonstrated with 8-bromo-cAMP and rolipram, without greatly affecting oxytocin-induced contractility. Hence there is a need for caution when considering the use of cAMP agonists as treatments for pre-term labour prevention due to the ability of prolonged [cAMP] elevation in promoting spontaneous contractions.