Evaluation of Medical Prefrontal Cortex (mPFC) Stimulation and Destruction Effects on Addiction to Morphine

Prefrontal cortex is one part of the regions contributed to addiction process and located at the frontal lobe of the brain. There is a central part of frontal lobe called medial prefrontal cortex (mPFC) plays an important role in the dopamine system network. The destruction or stimulation of cerebral nuclei such as ventral tegmental area (VTA) which is a part of the reward circuite can change the process of addiction. There is no evidence on clear role of mPFC in addiction; this research tried to determine the effects of destruction or stimulation of mPFC on producing addiction and reducing the signs of withdrawal syndrome. 60 male Wistar rats weighing 250-300 g were randomly selected and divided into four groups. The animals in tree groups (control، stimulated mPFC and destructed mPFC) received morphine for nine consecutive days as follow: 10 mg/kg for the first، 20 mg/kg for the second، and 40 mg/kg for third three-days. The Sham group received 0. 2 cc normal saline instead of morphine during the same period. On the tenth day، the withdrawal syndrome signs were measured. Each rat received 1 cc naloxone and the signs were recorded for one hour and compared through Kruskal-Wallis H test. The electrical stimulation of mPFC increased behaviors such as jumping، shaking the body and standing significantly (P < 0. 05)، whereas the destruction of mPFC significantly reduced withdrawal signs، such as standing and jumping compared to the control group (P < 0. 05); in one group، the shaking increased significantly (P < 0. 05). This research showed that electrical destruction of mPFC could decrease tendency to morphine. The most probable mechanism prevented an increase in withdrawal signs should be a decrease in the reward level induced by dopamine decrease in addiction cycle; the destruction of mPFC decreased dopamine concentration with acceptable effects on addiction and reward. The reverse occurred with the stimulation of that region.