Calcitonin gene-related peptide released by capsaicin suppresses myoelectrical activity of gastric smooth muscle.
BACKGROUND
It is widely accepted that the inhibition of gastric motor activity as well as the maintenance of gastric mucosal blood flow and mucous secretion are important for the homeostasis of the gastric mucosa. The present study was performed to ascertain whether or not capsaicin, which can protect the stomach from noxious stimuli, affects gastric motor activity.


METHODS
Male Sprague-Dawley rats were anesthetized with urethane, and the stomach was cannulated by two catheters from esophageal and duodenal sides. A biopolar electrode was fixed to the serosal surface of the antrum and myoelectrical activity was recorded during the instillation of a small volume of solutions.


RESULTS
The myoelectrical activity of rat gastric smooth muscle was increased at intragastric pressures of >2 cmH(2)O. Replacement of intragastric physiological saline with 1.6 mmol/L capsaicin solution significantly suppressed this myoelectrical activity by 50%. Intragastric capsaicin administration caused a significant release of substance P (SP) and calcitonin gene-related peptide (CGRP). The maximum released levels of CGRP in the gastric perfusates were 100-fold those of SP. The myoelectrical activity observed at an intragastric pressure of 2 cmH(2)O was avoided by continuous infusion of CGRP (0.1-3.0 nmol/kg per min) into the gastric artery in a dose-dependent manner, but not by that of SP (1.0 nmol/kg per min). Continuous CGRP-(8-37) infusion into the gastric artery completely blocked the reduction by intragastric capsaicin of myoelectrical activity.


CONCLUSIONS
These results suggest that the suppression of the myoelectrical activity of gastric smooth muscle by capsaicin is attributable to the endogenous CGRP released.
Mizuguchi
Sumito
S
Department of Internal Medicine, School of Medicine, Kitasato University, Sagamihara, Japan.
Ohno
Takashi
T
Hattori
Youichiro
Y
Kamata
Kazuhisa
K
Arai
Katsuharu
K
Saeki
Takeo
T
Saigenji
Katsunori
K
Hayashi
Izumi
I
Kuribayashi
Yoshikazu
Y
Majima
Masataka
M
D000704:Analysis of Variance; D000818:Animals; D015740:Calcitonin Gene-Related Peptide / Q000378:metabolism*; D002211:Capsaicin / Q000494:pharmacology*; D004576:Electromyography; D005753:Gastric Mucosa / Q000187:drug effects*; D008297:Male; D009130:Muscle, Smooth / Q000187:drug effects*; D016065:Myoelectric Complex, Migrating / Q000187:drug effects*; D051381:Rats; D017207:Rats, Sprague-Dawley
D015740:Calcitonin Gene-Related Peptide; D002211:Capsaicin