[Differences of intensities regarding withdrawal signs in experimental methods for inducing morphine dependency]

In the present study, we compared the intensity of physical dependency, mortality rate and weight changes in some common methods for inducing morphine dependency. Six common different methods for morphine dependency were chosen in wistar rats. In all methods, morphine dependency was induced by repeated morphine injection. Precipitation of morphine withdrawal signs were performed on the last day in each method, 4 hours after the last morphine injection for 20 minutes. The withdrawal signs included: vertical jumping, wet dog shakes, diarrhea, teeth chattering, ptosis, head shakes and rearing. Our results demonstrated that all groups of treated rats showed withdrawal signs following naloxone challenge. However, the intensities of withdrawal signs [vertical jumping, wet dog shakes, diarrhea, teeth chattering, head shakes and rearing] were significantly different among these methods. Also, mortality rate and amount of weight loss were significantly different among the different methods. This study demonstrates that different experimental methods of morphine dependency can induce different intensities of withdrawal signs, mortality rate and weight loss