Effect of Ghrelin on contractility of gastric smooth muscle in guinea pigs and the related mechanism

Abstract

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.