Effect of sildenafil, a phosphodiesterase-5 inhibitor, on oesophageal peristalsis and lower oesophageal sphincter function in cats

The propagation of oesophageal peristaltic contractions and lower oesophage al sphincter (LOS) relaxation depends on neural release of nitric oxide (NO ) which acts to increase intracellular cGMP. Sildenafil, a phosphodiesteras e-5 inhibitor that increases cGMP, reduces basal LOS pressure in patients w ith achalasia. We investigated the effect of sildenafil on the propagation of oesophageal contractions and LOS relaxation in the cat. Oesophageal mano metry was performed in five cats under light sedation. Peristaltic contract ions were monitored at 1, 2, 3, 4 and 8 cm proximal to the LOS, at the LOS using a Dent sleeve, and at 3 cm distal to the upper oesophageal sphincter. Swallow-induced oesophageal contractions and LOS relaxation were recorded during 30 min before and 30 min after intravenous administration of sildena fil. Sildenafil reduced the amplitude of oesophageal contractions only in t he smooth muscle oesophagus. The latency from swallow to distal oesophageal contractions was significantly delayed. LOS pressure was significantly red uced but the relaxation nadir was not modified by sildenafil. Sildenafil ha s profound effects on oesophageal motility: it modifies propagation and amp litude of oesophageal contractions and reduces LOS pressure, Slowing down t he propagation of contractions in the transitional zone between the striate d and smooth muscle can be a useful tool in patients with segmental perista lsis or intermittent simultaneous contractions, while the effect on the LOS can benefit patients with achalasia.