A 5-HT4 agonist mosapride enhances rectorectal and rectoanal reflexes in guinea pigs.
The rectal distension-evoked reflex rectal (R-R) contractions and internal anal sphincter (R-IAS) relaxations in guinea pigs were generated through the extrinsic sacral excitatory nerve pathway (pelvic nerves) and the intrinsic cholinergic excitatory and nitrergic inhibitory nerve pathways. The aim of the present study was to evaluate whether a prokinetic benzamide, mosapride, enhances the R-R and R-IAS reflexes mediated via 5-HT4 receptors in the guinea pig. The mechanical activities of the R and IAS were recorded with a balloon connected to a pressure transducer and a strain gauge force transducer in the anesthetized guinea pig with intact spinal-intestinal pathways. Gradual and sustained rectal distension evoked R-R contractions and synchronous R-IAS relaxations. Mosapride (0.1-1.0 mg/kg i.v.) dose-dependently enhanced both R-R and R-IAS reflex responses. Reflex indexes for R-R and R-IAS maximally increased from 1.0 (control) to 1.92 and 1.88, respectively. A specific 5-HT4 receptor antagonist, GR 113808 (1.0 mg/kg i.v.), antagonized the enhancement of the R-R and R-IAS reflexes induced by mosapride 1.0 mg/kg i.v. The present results indicate that mosapride enhanced the R-R and R-IAS reflexes mediated through 5-HT4 receptors.
Dept. of Physiology II, Nara Medical Univ., 840 Shijo-cho, Kashihara, Nara 634-8521, Japan.
Hidehiko
H
Shimatani
Yu
Y
Kojima
Makoto
M
Kadowaki
Tadashi
T
Nakagawa
Hisao
H
Fujii
Yoshiyuki
Y
Nakajima
Miyako
M
Takaki
D001003:Anal Canal / Q000294:innervation* / Q000502:physiology; D000818:Animals; D001549:Benzamides / Q000494:pharmacology*; D020117:Cisapride / Q000494:pharmacology; D006168:Guinea Pigs; D007211:Indoles / Q000494:pharmacology; D007275:Injections, Intravenous; D008297:Male; D009025:Morpholines / Q000494:pharmacology*; D009119:Muscle Contraction / Q000187:drug effects; D009126:Muscle Relaxation / Q000187:drug effects; D011985:Receptors, Serotonin / Q000502:physiology; D012007:Rectum / Q000294:innervation* / Q000502:physiology; D012018:Reflex / Q000187:drug effects*; D012702:Serotonin Antagonists / Q000494:pharmacology; D017366:Serotonin Receptor Agonists / Q000494:pharmacology*; D013449:Sulfonamides / Q000494:pharmacology; D014160:Transducers, Pressure
D001549:Benzamides; D007211:Indoles; D009025:Morpholines; D011985:Receptors, Serotonin; D012702:Serotonin Antagonists; D017366:Serotonin Receptor Agonists; D013449:Sulfonamides; C062720:mosapride; D020117:Cisapride; C082871:GR 113808