New models for the evaluation of opioid effects in the guinea‐pig ileum

Open Access
Publisher Website
Google Scholar
Abstract
The pharmacology of morphine and opioid peptides was studied in the guinea‐pig ileum by examining their inhibitory effects on propulsive peristaltic activity and on the cooling‐induced longitudinal contraction. In these experiments, dose‐response curves were recorded. The rank order of potency in inhibiting peristalsis was found to be: dermorphin> FK 33–824 > dynorphin‐(1–17)> dynorphin‐(1–13)> δ‐receptor‐peptide > morphine > [Leu] enkephalin, whereas the rank order in inhibiting cooling‐induced contractions was found to be: dynorphin‐(1–13) ⋍ FK 33–824 ⋍ dermorphin> δ‐receptor peptide > morphine. Naloxone antagonized the maximally effective dose of each of the opioid agents. In view of the differences between the abilities of these opioids to inhibit propulsive peristaltic activity, these models seem to be valuable for the examination of inhibitory opioid effects in the gut.