Morphine is a highly effective opiate analgesic, and is a valuable painkiller in modern medicine. However, the disadvantage of chronic morphine administration is the development of addiction with tolerance and dependence. Ideally, it would be advantageous to design therapeutics for effective analgesia, which lacks the addictive liabilities of morphine and related opiates. With this goal in mind, it is necessary to understand the biochemical pathways that mediate morphine-induced analgesia compared to tolerance, and dependence. Scientific advances often occur when new innovative technologies are applied towards elucidating specific research issues. Therefore, this R21 application for pilot, innovative studies utilizing state-of-the-art technologies in both proteomics and genomics, will elucidate molecular components involved in morphine-induced analgesia compared to tolerance or dependence. Notably, beta-arrestin knockout mice show distinct changes in morphine-induced actions corresponding to enhanced analgesia, absence of tolerance, and no change in dependence. These findings lead to the hypothesis of distinct biochemical pathways for these three parameters of morphine actions. Therefore, the goal of this feasibility project will be to utilize both proteomics and genomics to compare regulated molecular components in beta-arrestin knockout mice and wild-type mice during chronic morphine treatment, as a means to elucidate distinct biochemical pathways for morphine-induced analgesia compared to tolerance or dependence.
The specific aims are (1) proteomic evaluation of regulated proteins and peptides during chronic morphine in brains of beta-arrestin knockout mice compared to wild-type mice, and (2) genomic evaluation of differential gene expression during chronic morphine using unique neural-specific mouse cDNA microarrays in beta-arrestin knockout and wild-type mice. These studies will utilize state-of-the-art facilities for proteomics and mass spectrometry, and genomics with neural-specific mouse cDNA microarrays. Regulated gene products will be analyzed for primary sequence homology to gene families to predict their biological functions. Comparison of regulated gene products in beta-arrestin knockout and wild-type mice will allow assignment of regulated proteins and genes to candidate biochemical pathways involved in morphine analgesia, tolerance, or dependence. Elucidation of distinct pathways will be significant, since it could allow future design of opiate drug regimens that provide effective analgesia, without the tolerance and dependence of addiction.
