If channels encoded by HCN genes are important determinants of cardiac and neuronal excitability. If channels have also been recorded in smooth muscles but nothing is known about the impact of these channels to arterial contractility. This studied utilized end-point PCR to assess the expression of HCN genes in renal and mesenteric arteries from male Wistar rats (250-350 g) killed by cervical dislocation in accordance with Schedule 1 of the 1986 Animals Act. Isometric tension recordings were performed on segments of renal and mesenteric artery using a DMT myograph to assess the effect of recognized If channel blockers ZD7288 and zatebradine. Application of ZD7288 or zatebradine to rat renal arteries precontracted by 10 µM methoxamine produced a concentration-dependent relaxation that, at 30 µM, reached 53.9 ± 7.7% (n = 8) and 50.4 ± 19.4 % (n = 6) respectively. Relaxations produced by both agents waned considerably with prolonged application, and were greatly reduced when 60 mM KCl was used as the spasmogen. Similar results were observed in rat small mesenteric arteries but the If channel blockers were more potent (relaxations at 10 μM: ZD7288, 88.9 ± 8.6%; zatebradine, 83.8 ± 7.3%; n = 5 for both). Pre-incubation of both arteries with ZD7288 or zatebradine (≥ 10 μM) did not suppress contractions produced by the subsequent application of methoxamine. Using primers designed specifically against rat HCN1-4 produced amplicons in cDNA from rat brain and heart. However, only products to HCN1, 2 and 3 were detected in rat renal artery after 40 cycles. These data show that rat arteries express HCN genes and compounds that block the expression products of these genes are vasorelaxants