Characterization of the opiate receptor in the guinea-pig ileal mucosa.
Several opioid peptides and narcotic drugs reduced transepithelial potential difference (PD) and short circuit current (Isc) in guinea-pig ileal mucosa measured in vitro in Ussing chambers. [D-Ala2,D-Leu5]enkephalin was the most potent peptide tested. Enkephalin analogues with altered C-terminal amino acids were less potent, as were beta-endorphin and dermorphin. Etorphine produced potent effects whereas morphine and SKF 10,047 were inactive. Ethylketazocine produced a biphasic dose-response curve. When added by themselves diprenorphine and naloxone produced small increases in Isc. This effect was not seen when Cl- and HCO3- in the Ringer were replaced by SO42-. Diprenorphine and naloxone were able to shift the dose response curves for all agonists to the right, with the exception of that for ethylketazocine. Diprenorphine was a more potent antagonist than naloxone. SKF 10,047 also acted as a pure antagonist. Morphine and ethylketazocine had no antagonist effects. It is concluded that the opiate receptor in the guinea-pig ileal mucosa is similar to a delta-opiate receptor as defined by ligand binding studies, but that some differences also exist.
D000818:Animals; D004174:Diprenorphine / Q000494:pharmacology; D004745:Enkephalins / Q000494:pharmacology; D005260:Female; D006168:Guinea Pigs; D007082:Ileum / Q000032:analysis* / Q000187:drug effects; D066298:In Vitro Techniques; D007413:Intestinal Mucosa / Q000032:analysis / Q000187:drug effects; D009270:Naloxone / Q000494:pharmacology; D009294:Narcotics / Q000494:pharmacology; D011957:Receptors, Opioid / Q000187:drug effects / Q000302:isolation & purification*
D004745:Enkephalins; D009294:Narcotics; D011957:Receptors, Opioid; D004174:Diprenorphine; D009270:Naloxone