Neuropeptide Y inhibits Ca(2+)-activated K+ channels in vascular smooth muscle cells from the rat tail artery.

The effects of neuropeptide Y (NPY) on the Ca(2+)-activated K+ channel in smooth muscle cells from the rat tail artery were studied by whole-cell and single-channel patch-clamp recording techniques. In the presence of nifedipine (1 microM), whole-cell outward currents through Ca(2+)-activated K+ channels were inhibited by NPY in a dose-dependent manner from 20 to 200 nM. A maximum inhibition to about 48% of the control current could be achieved. Recordings from outside-out patches showed that the open probability of Ca(2+)-activated K+ channels were similarly inhibited by NPY. At 200 nM NPY, the open probability was reduced to about 36% of the control value. NPY did not affect the open times or current amplitude, but increased significantly the short (from 0.49 to 0.58 ms) and long (from 441 to 728 ms) closed times. Inhibition of Ca(2+)-activated K+ channels by NPY may contribute to its excitatory action on vascular smooth muscle cells.