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 chary bdotoxin-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 cAMR-dependent pathway in mouse lacrimal acinar cells.