Dual action effects of morphine on the electrical activity of the dorsal tegmentum.
The midbrain tegmentum has been identified as an important locus for development of negative reinforcement with electrical stimulation of the brain. It also plays a central role in the motivational-affective component of pain, and is a site of the analgesic action of morphine. The present study reports the effects of morphine on the electrical activity of areas of the dorsal tegmentum of rats that were also tested for the aversive effects of brain stimulation. The results of spectral analysis of the EEG indicated that IP injections of 16 mg/kg of morphine significantly depressed intensity of EEG, while 8 mg/kg of morphine tended to increase intensity. The results were interpreted in terms of the dual action hypothesis of morphine action and Winters' model of drug effects on electrical activity of the brain. It was concluded that morphine may produce complementary inhibitory and excitatory effects on the negative and positive reinforcement systems of the brain respectively.
D000818:Animals; D001522:Behavior, Animal / Q000187:drug effects; D004558:Electric Stimulation; D004567:Electrodes, Implanted; D004569:Electroencephalography; D008297:Male; D009020:Morphine / Q000494:pharmacology*; D051381:Rats; D013681:Tegmentum Mesencephali / Q000033:anatomy & histology / Q000187:drug effects*
D009020:Morphine