Study On The Regulations Of Ghrelin,GHRP-6 And Motilin On Gastrointestinal Motility In Rats

Objective: Ghrelin,a 28-amino acid peptide have a variety of other functions have been ascribed to ghrelin,including cardiovascular(anti)-proliferative and slow wave sleep promoting effects.The physiological role of motilin is related to the induction of the interdigestive motility pattern and gastric emptying.To investigate the effects of ghrelin,the ghrelin receptor agonist,growth hormone releasing peptide 6(GHRP-6)and motilin on gastrointestinal motility in rats and to explore the underlying mechanisms.Methods: The effects of ghrelin,GHRP-6 and motilin on gastric emptying and intestinal propulsion in rats were observed by intraperitoneal injection;In vitro experimental observation the effect of ghrelin,GHRP-6 and motilin on the fundic or antral strips responses to electrical field stimulation(EFS);RT-PCR was used to observe the expression of ghrelin and m RNA in the stomach;Western blot was used to observe the expression of GHSR in the stomach;.Results: 1.The results of in vivo study showed that compared with normal saline(NS)group,intraperitoneal injection of 30 ?g / kg ghrelin(P<0.05)and 60 ?g / kg(P <0.01)ghrelin could significantly increase the gastric emptying rate in rats.But the gastric emptying rate of rats in ghrelin 10?g / kg group and 120?g / kg group did not change significantly(P>0.05).The effect of ghrelin on the gastric emptying rate of rats show a dose dependent(P<0.05~0.01);The results show that,compared with NS group,intraperitoneal injection of ghrelin(10?g/kg?30?g/kg?60 ?g/kg?120?g/kg)only at a concentration of only 60?g / kg,rat intestinal peristalsis increased significantly(P<0.05).2.In the results of the study show that,compared with NS group,rats were intraperitoneally injected with 10 ?g/kg,40 ?g/kg,80 ?g/kg,120 ?g/kg GHRP-6,gastric emptying rate increased(P<0.05-0.01),and showed a dose dependent relationship,indicating that GHRP-6 promotes gastric emptying;The results of the study show that,compared with the NS group,rats were given intraperitoneal injection of 40 ?g/kg,100 ?g/kg and 120 ?g/kg GHRP-6 after intestinal propulsive rate increased(P<0.05-0.01),and showed significant dose dependent relationship.3.compared with group NS,intraperitoneal injection of 120 g/kg motilin significantly increased the gastric emptying rate in rats(P<0.05),but compared with NS group,the effect of the intraperitoneal injection of motilin(20,120 ?g/kg)had no significant on intestinal propulsive rate(P>0.05).4.When the rats were given L-NAME(250 ?M),the smooth muscle turned from relaxation response to contractile response(P<0.05),so it was concluded that the relaxation reaction induced by electric stimulation might be mediated by NO.In the absence of adrenergic or cholinergic conditions(NANC,5×10-6 mol/L atropine and 3×10-6 mol/L guanethidine),the contractile response of gastric smooth muscle(P<0.05)disappeared after the off-stimulation,so it was concluded that the contractile response induced by electrical stimulation may be mediated by cholinergic agents.5.The results showed that 2 ?M ghrelin inhibited the relaxation response of stomach fundus smooth muscle at 1 Hz and 8-16 Hz EFS(P<0.05~0.01),and enhanced contractile responses in stomach fundus smooth muscle at 4-8 Hz EFS(P < 0.05~0.01).The study also found that,given 4 Hz EFS,rats were treated with L-NAME could enhance ghrelin induced gastric smooth muscle contraction(P<0.05);given 2 ?M GHRP-6 in stomach fundus smooth muscle relaxation response was inhibited at the 2 Hz and 16 Hz EFS(P < 0.01),and contractile response was enhance at the 8-16 Hz under EFS(P < 0.05~0.001).The study also found that the 2-8Hz EFS,L-NAME enhanced GHRP-6 induced gastric smooth muscle contractile function(P<0.01~0.001);The effect of 2 ?M of motilin on gastric fundus smooth muscle at 1 Hz and 1-16 Hz EFS had no significant(P>0.05).The results showed that motilin did not affect the contractile response of the gastric fundus smooth muscle after administration of L-NAME(P > 0.05).6.After the EFS,the gastric antrum smooth muscle did not appear the relaxation reaction similar to that of the gastric fundus smooth muscle under the EFS,but there was obvious contraction reaction under the off-electric stimulation.And the gastric smooth muscle contraction reaction was enhanced after treat with L-NAME,indicating gastric antrum smooth muscle contraction under off-electric stimulation may be mediated by cholinergic.rats were given NANC(5 ?M atropine and 3 ?M guanethidine mixture)completely blocked the EFS-evoked gastric smooth muscle contractile response(P>0.05).7.The results showed that the contractile response of the gastric antrum smooth muscle at 4-16 Hz EFS was increased by 2 ?M ghrelin or 2 ?M GHRP-6(P<0.05~0.01);L-NAME pre-incubation of muscle strips significantly enhanced ghrelin(1-8Hz)-induced antral smooth muscle contraction(P<0.05);L-NAME could enhance GHRP-6(1-16Hz)induced gastric smooth muscle contraction(P<0.05~0.01);The results showed that 2 ?M motilin had no effect on smooth muscle under the different intensity of electric stimulation,after giving L-NAME is still no effect on motilin induced gastric smooth muscle contraction and relaxation responses(P > 0.05)..8.RT-PCR results showed that there is ghrelin receptor m RNA in antral strips and fundic strips.Western blot results showed that there is GHSR in antral strips and fundic strips.Conclusion: The order of promoting gastric emptying or intestinal transit was as follows ghrelin,GHRP-6,motilin;the relaxation and contractile response of the rat gastric antrum and fundus smooth muscle is mediated by the nervus;the electrical stimulation of the relaxation response may be mediated by NO,the stimulation of the power to stimulate the response may be mediated by the choline;ghrelin and GHRP-6 can promote gastric smooth muscle relaxation and contractile,the effect may be related to the NO signal pathway.