The effect of Orexin type 1 receptor antagonism on Paragigantocellularis nucleus during the development of naloxone induced morphine withdrawal syndrome in male wistar rats

According to studies, evidence indicating that orexin neuropeptides and Paragigantocellularis (PGi) nucleus neurons that located in the rostroventromedial medulla oblongata (RVMM) region, involved in expression of opiates induced by physical dependence and withdrawal syndrome signs. Orexin type 1 receptors which are present throughout RVMM region, appear mainly in the Lateral PGi (LPGi) nucleus. In this study were examined the effect of orexin receptor on behavioral symptoms withdrawal syndrome with administration orexin type 1 receptor antagonist (SB 334867) into the PGi nucleus. Inhibition of orexin type 1 receptor by antagonist hinder the process of creating dependency reduces behavioral signs of naloxone and induced morphine withdrawal syndrome. In this way male wistar rats weighing 250-300 g the number 4 in each cage with a dark-lighting cycle of 12 hr were used. Creating dependency through subcutaneous injection of morphine (10mg/kg, 1ml) 2 times per day at an interval of 12 hours for 7 days. At the seventh day, 2 hours after administration of morphine, naloxone (2.5mg/kg, 1ml) was injected intraperitoneally (IP) and withdrawal symptoms in a 25 minute period while the animal was placed in a transparent cage were counted. In main group of animals jnjected intra-LPGi SB334867 ( 0.2 µl, 100 µM ) for 7 days before each morphine injections were given. In the control group, SB Vehicle (DSMO 1%, 0.2 µl) was injected such the main group. The results showed that the inhibition of orexin type 1 receptor LPGi nucleus Reduces number of behavioral signs of naloxone induced morphine withdrawal syndrome .