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Title: Gastric acid secretion by central injection of dynorphin A-(1-17), an endogenous ligand of kappa-opioid receptor, in urethane-anesthetized rats. Author: Ishihara S, Tsuchiya S, Horie S, Murayama T, Watanabe K. Journal: Jpn J Pharmacol; 2001 Sep; 87(1):14-20. PubMed ID: 11676193. Abstract: Gastric acid secretion has been proposed to be regulated by opioid receptors in the central nervous system (CNS). Previously, we reported that central injection of synthetic agonists of kappa-opioid receptors stimulated gastric acid secretion in rats, and the secretion by the agonists was inhibited by norbinaltorphimine (an antagonist of kappa-opioid receptor). In the present study, we investigated the effect of dynorphin A-(1-17), an endogenous ligand of kappa-opioid receptor on the gastric acid secretion in the perfused stomach of urethane-anesthetized rats. Injection of dynorphin A-(1-17) (0.1-1 microg per rat) into the lateral cerebroventricle (LV) stimulated the secretion in a dose-dependent manner. The effect of dynorphin A-(1-17) was almost completely inhibited by the LV injection of norbinaltorphimine (10 microg) and in vagotomized rats. Although some studies of dynorphin A-(1-17) after central injection showed non-opioid effects such as the involvement of N-methyl-D-aspartate (NMDA) receptor, the effect of dynorphin A-(1-17) was not inhibited by a selective antagonist of the NMDA receptor ((+/-)-3-(2-carboxypiperazin-4-yl)-1-propylphosphonic acid, 10 microg). The LV injection of naloxone benzoylhydrazone (a kappa3-opioid receptor agonist, 100 microg) also stimulated the secretion in norbinaltorphimine-sensitive manner. These findings showed that both an endogenous ligand dynorphin A-(1-17) and a synthetic kappa3-opioid receptor agonist stimulated gastric acid secretion via kappa-opioid receptors in the CNS of rats in vivo.[Abstract] [Full Text] [Related] [New Search]