اثر استرس شنا بر توسعه روند كيندلينگ شيميايي توسط پنتيلن تترازول در موش صحرايي : نقش گلوكوكورتيكوييدها و اپيوييدها

Effect of Swimming Stress on the Development of Chemical Kindling Induced by Pentylene-etrazole in Rat: Role of Glucocorticoids and Opioids

Background: Stress causes glucocorticoids (GCs) and endogenous opioids release. Some steroids have inhibitory effects on convulsion but others are convulsive. Endogenous opioid mechanisms may aggravate stress-induced seizures. Swimming at 20°c for 3 min [swimming stress, (SS)] delays the onset of convulsions induced by pentylenetetrazole (PTZ) and aggravates electroshock-induced seizures. In this study we evaluated the effect of repeated swimming stress on repeated injection of PTZ for induction of chemical kindling. Materials and Methods: 56 Wistar rats were divided into 7 groups ( eight in each group). Animals were chemically kindled by PTZ injections (45mg/kg) given intraperitoneally every 48h. To evaluate the effect of GCs and endogenous opioids 30 mins before PTZ injection, metyrapone (an inhibitor of GCs synthesis) and naloxone as an opioid receptor antagonist were injected. Results: Kindling Process was aggravated by SS, whereas inducing the fifth stage of chemical kindling in SS group decreased from 4.9±1.06 days to 3.3±0.96 in PTZ group. Kindling was completely prevented by injection of metyrapone prior to PTZ injection. Mean values of the seizure stages in different days (except in the second and sixth days) in this group were significantly decreased compare to PTZ group. Naloxone pretreatment delayed the process of kindling whereas, the mean days inducing fifth stage of kindling was increased to 9±2.05 days, and in this group, 50% of animals became kindled. Application of stress 30 min after naloxone, aggravated the process of kindling and in this group all of animals became kindled. Conclusion: The results of this study showed that swimming stress increases the development of PTZ-induced kindling, probably through releasing of GCs and endogenous opioids. The mu opioid receptors may have an important role in the expression of opioid effects.