Vasoactive intestinal peptide activates Ca2(+)-dependent K+ channels through a cAMP pathway in mouse lacrimal cells

The action of vasoactive intestinal peptide (VIP) on Ca2(+)-dependent K+ currents, in dissociated mouse lacrimal cells, was investigated using patch clamp techniques. In whole cell recordings, VIP (10-100 pM) increased the magnitude of the Ca2(+)-dependent K+ current. In single channel recordings, VIP increased the fraction of time the large charybdotoxin-sensitive Ca2(+)-activated K+ channel spent in the open state. The activity of this channel was also increased by adding forskolin or 8-bromo cAMP to the bath. Additionally, application of either cAMP or catalytic subunit of cAMP-dependent protein kinase directly to the cytoplasmic surface of excised inside out patches reversibly lengthened the time Ca2(+)-activated K+ channels spent in the open state. These data suggest that VIP stimulates Ca2(+)-activated K+ channels by a cAMP-dependent pathway in mouse lacrimal acinar cells.