Central effect of mu-opioid agonists on antral motility in conscious rats.

Published

Journal Article

Centrally applied opioids delay gastric emptying and inhibit intestinal transit. However, the mechanism of inhibitory effects of central opioids on gastric motility still remains unclear. It also remains unclear which opioid receptor (mu, delta, and kappa) stimulation affects gastric motility. We studied the central effect of opioids on antral motility in conscious rats. A strain gauge transducer was implanted on the gastric antrum to record the circular muscle contractions. The area under the curve of the antral motility, calculated as a motility index, was evaluated before and after the intracerebroventricular (icv) injection of various opioid agonists in each rat. [D-Ala2, N-Me-Phe4, Gly5-ol] enkephalin (DAMGO, 0.1-10 nmol), a mu-opioid selective agonist, significantly inhibited antral motility in a dose-dependent manner (n=4). The motility index was significantly decreased to 47.3+/-10.8% (n=4) of controls at 20 min after icv injection of DAMGO (1.0 nmol). In contrast, [D-pen2, L-Pen5] enkephalin (DADLE, 1.0 nmol), a delta-opioid selective agonist, and U50,488 (1.0 nmol), a kappa-opioid selective agonist, had no significant effects on antral motility. Pretreatment with subcutaneous guanethidine (5 mg/kg) and propranolol (1 mg/kg), but not phentolamine (1 mg/kg), significantly antagonized the inhibitory effect of DAMGO (1.0 nmol). Reduced motility index induced by DAMGO (1.0 nmol) was restored from 48.7+/-3.5% to 88.6+/-10.9% (n=5) and 80.4+/-2.2% (n=5) by guanethidine and propranolol, respectively. Our findings suggest that central mu-opioid receptor has major inhibitory effects on antral motility in conscious rats. The inhibitory effects of mu-opioid receptors are mediated via sympathetic pathways and beta-adrenoceptors.

Full Text

Duke Authors

Cited Authors

  • Tsuchida, D; Fukuda, H; Koda, K; Miyazaki, M; Pappas, TN; Takahashi, T

Published Date

  • October 2004

Published In

Volume / Issue

  • 1024 / 1-2

Start / End Page

  • 244 - 250

PubMed ID

  • 15451387

Pubmed Central ID

  • 15451387

Electronic International Standard Serial Number (EISSN)

  • 1872-6240

International Standard Serial Number (ISSN)

  • 0006-8993

Digital Object Identifier (DOI)

  • 10.1016/j.brainres.2004.07.081

Language

  • eng