Effect of Opioid Agonists , Diazepam and Ketamine on the Estrous and Pregnant Rat Uteri , in Vitro

Kim, Chi Hyo; Lee, Choon Hi

Abstract

Opiates have been used as analgesics in obstetrics since the Babylonian Sinee that time, a wide variety of opiates have been employed in an attempt to provide analgesia for childbirh. The effect of opioids on uterine contractility is of considerable interest. Morphine caused a concentration dependent decrease in the frequency of contraction of the estrous uterus, In contrast, both pethidine and pentazocine enhanced the contraction rate. The pregnant uterus showed little response to morphine, but exhibited an enhanced response to the stimulant activity of both pethidine and pentazocine.It has long been recognized that the tension development of uterine muscle is largely dependent on intracellular Ca2+ pools. Smooth muscle contraction is initiated by depolarization induced calcium entry into the myoplasm through voltage dependent calcium channels, The spontaneous or KC1-induced tension development in isolated uterine smooth musele is reduced by lowering the calium ion (Ca2+) concentration of the bathing medium. In our study, the effect of morphine, pethidine and pentazocine on estrous and pregnant uterine activity, and the effect of extracellular calcium on opiate induced uterine motility have been examined in rats in vitro The following results were obtained: 1) The frequency of contraction of the estrous and pregnant rat uteri in the control group decreased gradually with time. 2) Morphine caused a concentration- dependent decrease in the frequency of contraction of the estrous and pregnant rat uteri, but it was not significant 3) Pethidine and pentazocine caused a concentration dependent incrase in the frequency of contraction of the estrous and pregnant rat uteri.but it was not significant.4) Diazepam caused a concentration-dependent decrease in the frequency of contraction of the estrous and pregnant rat uteri. 5) Ketamine casued a concentration- dependent decrease in the frequency of contraction of the estrous and pregnant rat uteri, but it was not significant. 6) Addition of CaCI, to the Krebs Henseleit solution did not make any significant change in the result. 7) According to the condition of the estrous and pregnant rat uteri the change of contraction frequency was statistically significant in the control, morphine, pethidine and pentazocine groups.