Differences in the bimodal effects of morphine in the vas deferens of two strains of rats.
1. The effect of morphine on the smooth muscle of the isolated vas deferens of Sprague-Dawley and Wistar rats was studied. 2. Morphine produces pre- and post-synaptic effects on the contractile activity of the vasa deferentia. 3. The pre-synaptic action is an increase in the basal tension of the vas deferens. 4. The post-synaptic effect is a bimodal change in the height of the muscular twitch induced by neurogenic transmural stimulation. 5. Sprague-Dawley rats are more sensitive than Wistar rats to the actions of morphine. 6. The morphine induced responses were antagonized by naloxone better in Wistar than Sprague-Dawley rats. 7. The findings obtained suggest a genetic differences in the synthesis of opioid subtype receptors.
Department of Pharmacology, Faculty of Medicine, Universidad de Chile, Santiago.
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Bustamante
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Miranda
D000818:Animals; D004558:Electric Stimulation; D008297:Male; D009020:Morphine / Q000494:pharmacology*; D009130:Muscle, Smooth / Q000187:drug effects*; D051381:Rats; D011919:Rats, Inbred Strains; D013045:Species Specificity; D014649:Vas Deferens / Q000187:drug effects
D009020:Morphine