Hyperpolarization-activated cyclic-nucleotide-modulated (HCN) channels mediate the pacemaker current (I_h or I_f) observed in electrically rhythmic cardiac and neuronal cells. Here we describe a hyperpolarization-activated time-dependent cationic current, -I_h, in pancreatic -cells. Transcripts for HCN1-4 were detected by RT-PCR and quantitative PCR in rat islets and MIN6 cells. -I_h in rat -cells and MIN6 cells displayed biophysical and pharmacological properties similar to those of HCN currents in cardiac and neuronal cells. Stimulation of cAMP production with forskolin/IBMX (50 µM) or db-cAMP (1 mM) caused a significant rightward shift in the midpoint activation potential of -I_h, while expression of either a specific siRNA construct (siHCN2b) against HCN2 or a dominant-negative HCN channel (HCN1-AAA) caused a near-complete inhibition of time-dependent -I_h. However, expression of siHCN2b in MIN6 cells had no affect on glucose-stimulated insulin secretion under normal or cAMP-stimulated conditions. Blocking -I_h in intact rat islets also did not affect membrane potential behaviour at basal glucose concentrations. Taken together, our experiments provide the first evidence for functional expression of HCN channels in the pancreatic -cell.