The goal of the proposed studies will be to understand how and where narcotic drugs may control cerebral RNA and protein metabolism during the development of tolerance. The quantitative, qualitative and temporal changes produced by morphine in messenger and preribosomal RNA, nascent polypeptide, amino acid, nucleotide and total RNA and protein metabolism in various regions of the brain will be related to the development of tolerance to the analgesic and hypothermic actions of morphine. The efficacy of narcotic antagonists in blocking the development of acute tolerance to morphine will be correlated with their effects on RNA and protein metabolism. The efficacy of actinomycin D and cycloheximide in blocking the development of acute tolerance to morphine will be correlated with their effects on morphine levels in the brain and on messenger RNA, nascent polypeptide and total RNA and protein metabolism in the brain. Evidence that narcotics alter cerebral RNA and protein metabolism is contradictory. In contrast, studies with RNA and protein synthesis inhibitors suggest that new RNA and protein synthesis may be involved in the development of tolerance to and physical dependence on morphine. However, the biochemical consequences of nonspecific effects of inhibitors are unpredictable. The relationship between the development of narcotic tolerance and regional RNA and protein metabolism in the brain has not been defined. Brains from normal, acutely morphinized and morphine tolerant rats will be frozen in some cases, removed and dissected into 7-10 regions. Animals will be injected intraventricularly with labeled RNA and/or protein precursors prior to death. Messenger and ribosomal RNA, free and bound polysomes, nascent polypeptides, amino acids, nucleotides and total RNA and protein will be prepared. Techniques of liquid scintillation spectrometry, spectrophotometry, chromatography, electrophoresis and sucrose density gradient sedimentation will be employed to analyze populations of macromolecules. These experiments will provide data on the relationship between narcotic drugs and RNA and protein metabolism and how they relate to the development of tolerance.