Role of enkephalins in regulation of basal intestinal water and ion absorption in the rat.
Intraluminal administration of naloxone (10(-4) M), a mu-opiate receptor antagonist, or diprenorphine (10(-6) M), an opiate receptor antagonist with high affinity for both delta- and mu-receptors, decreased basal in vivo water and electrolyte absorption in the jejunum and ileum but not the colon of the rat. Diprenorphine (10(-5) M) decreased basal colonic water transport. These changes were not due to a reduction in mucosal Na-K-ATPase activity. Intravenous atropine prevented as well as abolished the changes in water transport due to naloxone. The diprenorphine-induced changes were not altered by atropine. Naloxone and diprenorphine acted by different receptors. Pretreatment with naloxone (10(-4) M) prevented the increase in water transport due to morphine, a mu-agonist, whereas a higher concentration of naloxone (10(-3) M) was required to inhibit the increase due to D-Ala-methionine-enkephalinamide, a delta-receptor agonist. In contrast, diprenorphine (10(-6) M) abolished the absorption caused by morphine and D-Ala-methionine-enkephalinamide. Diprenorphine (3 X 10(-7) M) partially prevented the morphine-induced increase in water absorption.(ABSTRACT TRUNCATED AT 250 WORDS)
D000818:Animals; D001285:Atropine / Q000494:pharmacology; D003106:Colon / Q000187:drug effects; D004174:Diprenorphine / Q000494:pharmacology; D004745:Enkephalins / Q000502:physiology*; D007421:Intestine, Small / Q000187:drug effects*; D008297:Male; D009020:Morphine / Q000494:pharmacology; D009270:Naloxone / Q000494:pharmacology; D051381:Rats; D011957:Receptors, Opioid / Q000187:drug effects*; D017450:Receptors, Opioid, mu; D014882:Water-Electrolyte Balance / Q000187:drug effects*
D004745:Enkephalins; D011957:Receptors, Opioid; D017450:Receptors, Opioid, mu; D004174:Diprenorphine; D009270:Naloxone; D009020:Morphine; D001285:Atropine