Effects of YF476 and Rabeprazole on Gastric Function

The primary objectives are to find out in healthy subjects if: * YF476 prevents the ECL-cell hyperplasia induced by repeated doses of rabeprazole - a proton pump inhibitor; * YF476 also prevents rebound hyperacidity after stopping rabeprazole; and * YF476 by itself causes neither ECL-cell hyperplasia after repeated doses nor rebound hyperacidity after stopping YF476. The secondary objectives are to: * assess the safety and tolerability of YF476, alone and in combination with rabeprazole; * compare the effects of YF476, alone and in combination with rabeprazole, on serum gastrin and plasma CgA and SST; * assess if there is a pharmacokinetic interaction between YF476 and rabeprazole; * assess the pharmacokinetics of repeat doses of YF476 by itself; and * study the metabolism of YF476.