We previously found that addition of cAMP and a Ca²⁺-/PKC-dependent agonist causes synergism or potentiation of protein secretion from rat lacrimal gland acini. In the present study we determined if cAMP decreases p44/p42 mitogen activated protein kinase (MAPK) activity in the lacrimal gland. As we know that activation of MAPK attenuates protein secretion stimulated by Ca²⁺- and PKC- dependent lacrimal gland secretion, we also determined if this activation cause potentiation of secretion. Freshly prepared rat lacrimal gland acinar cells were incubated with dibutyryl cAMP (dbcAMP), carbachol (a cholinergic agonist), phenylephrine (an ₁-adrenergic agonist) or, epidermal growth factor (EGF). The latter three agonists are known to activate p44/p42 MAPK. p44/p42 MAPK activity and protein secretion were measured. As measured by western blot analysis, dbcAMP inhibited both basal and agonist-stimulated p44/p42 MAPK activity. Cellular cAMP levels were increased by: 1) using two different cell permeant cAMP analogs, 2) activating adenylyl cyclase (L85 8051), or 3) activation of Gs-coupled receptors (VIP). Cell permeant cAMP analogs, L85 8051, and VIP inhibited basal p44/p42 MAPK activity by 50%, 40%, and 40%, respectively. dcAMP and VIP inhibited carbachol- and EGF-stimulated MAPK activity. cAMP, but not VIP, inhibited phenylephrine-stimulated MAPK activity. Potentiation of secretion was detected when carbachol, phenylephrine, or EGF were simultaneously added with dbcAMP. We conclude that increasing cellular cAMP levels inhibits p44/p42 MAPK activity and that this could account for potentiation of secretion obtained when cAMP was elevated and Ca²⁺ and PKC were increased by agonists.