Developmental changes in morphine and clonidine sensitivity of isolated chick oesophagus.
1. Electrically evoked contractions of isolated newly-hatched and over 6 week-old chicks cervical oesophagus (pre-crop) were inhibited by morphine and clonidine in a dose-dependent manner. 2. The inhibitory effects of morphine and clonidine were antagonized by naloxone (3 x 10(-6) M) and yohimbine (10(-7) M), respectively. 3. IC50 for morphine was 1.01 x 10(-7) M for newly-hatched and 5.19 x 10(-6) M for adult chicks. 4. IC50 for clonidine was 2.34 x 10(-9) M for newly-hatched and 1.19 x 10(-8) M for adult chicks. 5. These findings indicate a significant decrease in inhibitory effect of morphine and clonidine during developmental stages.
Dehpour
A R
AR
Department of Pharmacology, Faculty of Medicine, Tehran University of Medical Sciences, Iran.
Ghahremani
M H
MH
D000818:Animals; D002645:Chickens; D003000:Clonidine / Q000494:pharmacology*; D004361:Drug Tolerance; D004558:Electric Stimulation; D004947:Esophagus / Q000187:drug effects / Q000254:growth & development*; D005260:Female; D066298:In Vitro Techniques; D008297:Male; D009020:Morphine / Q000494:pharmacology*; D024510:Muscle Development; D009130:Muscle, Smooth / Q000187:drug effects / Q000254:growth & development*; D009270:Naloxone / Q000494:pharmacology
D009270:Naloxone; D009020:Morphine; D003000:Clonidine