Acute morphine administration, morphine dependence, and naloxone-induced withdrawal syndrome affect the resting-state functional connectivity and Local Field Potentials of the rat prefrontal cortex

Opiates are among the widely abused substances worldwide. Also, the clinical use of opioids can cause unwanted and potentially severe consequences such as developing tolerance and dependence. This study simultaneously measured the changes induced after morphine dependence and naloxone-induced withdrawal syndrome on the resting-state functional connectivity (rsFC) and Local Field Potential (LFP) power in the prefrontal cortex of the rat. The obtained results revealed that acute morphine administration significantly increased the LFP power in all frequency bands, as well as the rsFC strength of the prefrontal cortex, and naloxone injection reversed this effect. In contrast, chronic morphine administration reduced neural activity and general correlation values in intrinsic signals, as well as the LFP power in all frequency bands. In morphine-dependent rats, after each morphine administration, the LFP power in all frequency bands and the rsFC strength of the prefrontal cortex were increased, and these effects were further enhanced after naloxone precipitated withdrawal syndrome. The present study concludes that general correlation merely reflects the field activity of the local cortices imaged.