Inhibitory opioid receptors in canine pylorus.
In 18 anesthetized dogs, antroduodenal and pyloric motility was monitored in vivo by a sleeve and perfused side-hole manometric assembly and by antral and duodenal serosal strain gauges. Close intra-arterial injection to the pylorus of dynorphin-(1-13) (Dyn) for kappa-receptors, [D-Pen2,5]enkephalin (DPen2,5-Enk) for delta-receptors, and [N-Me-Phe3-D-Pro4]morphiceptin (PL017) and [D-Ala2,N-Me-Phe4,Gly5-ol]enkephalin (DAGO) for mu-receptors showed no excitatory effect in the pylorus. When pyloric motor activity was increased by duodenal field stimulation 3-5 cm aboaad from the pylorus, Dyn greater than DPen2,5-Enk greater than DAGO produced a dose-dependent inhibition of the pyloric motor activity. Naloxone (200 micrograms/kg iv and 20 micrograms ia) had no effect on the pyloric excitation due to duodenal field stimulation, but it reduced the inhibitory response of intra-arterially injected opioids. In addition, opioid binding ([3H]diprenorphine) in microsomal and mitochondrial fractions from the inner circular muscle ring of the pylorus showed a distribution similar to the neuronal marker [3H]saxitoxin but no correlation to the plasma membrane marker 5'-nucleotidase. These results suggest the existence of inhibitory opioid receptors (kappa- and delta-receptors) on excitatory neurons in the intestinal neuronal pathway, which activates the canine pylorus.
Allescher
H D
HD
Department of Neurosciences, McMaster University, Hamilton, Ontario, Canada.
Ahmad
S
S
Daniel
E E
EE
Dent
J
J
Kostolanska
F
F
Fox
J E
JE
D000818:Animals; D004174:Diprenorphine / Q000378:metabolism; D004285:Dogs; D004386:Duodenum / Q000502:physiology; D004558:Electric Stimulation; D004745:Enkephalins / Q000494:pharmacology; D005260:Female; D007700:Kinetics; D008297:Male; D009270:Naloxone / Q000494:pharmacology; D009294:Narcotics / Q000494:pharmacology*; D011312:Pressure; D011706:Pyloric Antrum / Q000187:drug effects / Q000502:physiology; D011708:Pylorus / Q000187:drug effects / Q000502:physiology*; D011957:Receptors, Opioid / Q000187:drug effects / Q000502:physiology*; D012530:Saxitoxin / Q000378:metabolism
D004745:Enkephalins; D009294:Narcotics; D011957:Receptors, Opioid; D004174:Diprenorphine; D012530:Saxitoxin; D009270:Naloxone