Objective:To investigate and compare the influences of Ghrelin and growth hormone releasing peptide 6 (GHRP6) on the contractility of stomach smooth muscle in guinea pigs, and to study the related mechanism.Methods: The myenteric plexuses of gastric fundus and antrium in guinea pigs were stimulated with electrical field stimulation (EFS) to observe the influence of Ghrelin and GHRP6 on the contractility of stomach smooth muscle. The influences of NnitroLarginine (LNNA) and LArginine (LAA) on the effect of Ghrelin and GHRP6 were studied to disclose the mechanism of the effects of Ghrelin and GHRP6. Results: The circular muscle tissues of the gastric fundus generated onrelaxations and offcontractions when stimulating myenteric plexuses with 116 Hz electrical field; the onresponses induced relaxation could be reduced by LNNA and the offcontractions induced contraction could be blocked by atropine and guanethidine. In fundic strips, ghrelin and GHRP6 could decrease the onresponse induced relaxation and increase offresponse induced contraction of the muscle, with the effect of Ghrelin obviously stronger than that of GHRP6.LNNA could increase the effects of Ghrelin and GHRP6induced muscle contraction, and LAA could decrease their effects. In the antral strips, electrical field stimulation of myenteric plexuses led to disappearance of relaxation wave, only leaving offcontractions. Both ghrelin and GHRP6 could increase that contraction.Conclusion: Both ghrelin and GHRP6 can promote the contractility of stomach smooth muscle in guinea pigs through stimulating myenteric plexuses of gastric fundus and antrium, which might be related to the NO pathway.