A comparative study on the effects of new opioid compounds and morphine on the contractility of guinea pig ileum and mouse vas deferens

Considering the clinical significance of opioids, especially their application for the treatment of severe painful conditions including cancer pain and the requirement for the synthesis of more specific drugs with lower side effects, this study was conducted to perform a preliminary investigation on six newly developed opioid drugs. Our aim was to introduce drugs that act selectively on the opioid µ or δ receptors. Since the inhibitory effect of the opioids on the smooth muscle ceIls has already been proved, we have decided to investigate the inhibitory effect of new drugs in this family on the contraction of guinea pig ileum and mouse vas deferens. Each drug was tested for 6 times and the results were evaluated through comparing their IC50 with morphine and with other drugs regarding MVDIC50/GPI IC50 Ratio. The results showed that ail new drugs have inhibitory effects on the muscle twitch, which indicates their agonistic property. Secondly, the new drugs were more selective for µ receptors than δ ones. Third, drug F in guinea pig didn't produce any significant effect in comparison with morphine, but the observed difference for drugs A, B, C, D, and E were significant as compared to morphine. Furthermore, all of them had significant effect on mouse vas deferens in comparison with morphine