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Functionally selective signaling for morphine and fentanyl antinociception and tolerance mediated by the rat periaqueductal gray.

ABSTRACT: Functionally selective signaling appears to contribute to the variability in mechanisms that underlie tolerance to the antinociceptive effects of opioids. The present study tested this hypothesis by examining the contribution of G protein-coupled receptor kinase (GRK)/Protein kinase C (PKC) and C-Jun N-terminal kinase (JNK) activation on both the expression and development of tolerance to morphine and fentanyl microinjected into the ventrolateral periaqueductal gray of the rat. Microinjection of morphine or fentanyl into the periaqueductal gray produced a dose-dependent increase in hot plate latency. Microinjection of the non-specific GRK/PKC inhibitor Ro 32-0432 into the periaqueductal gray to block mu-opioid receptor phosphorylation enhanced the antinociceptive effect of morphine but had no effect on fentanyl antinociception. Microinjection of the JNK inhibitor SP600125 had no effect on morphine or fentanyl antinociception, but blocked the expression of tolerance to repeated morphine microinjections. In contrast, a microinjection of Ro 32-0432 blocked the expression of fentanyl, but not morphine tolerance. Repeated microinjections of Ro 32-0432 blocked the development of morphine tolerance and inhibited fentanyl antinociception whether rats were tolerant or not. Repeated microinjections of SP600125 into the periaqueductal gray blocked the development of tolerance to both morphine and fentanyl microinjections. These data demonstrate that the signaling molecules that contribute to tolerance vary depending on the opioid and methodology used to assess tolerance (expression vs. development of tolerance). This signaling difference is especially clear for the expression of tolerance in which JNK contributes to morphine tolerance and GRK/PKC contributes to fentanyl tolerance.

SUBMITTER: Morgan MM

PROVIDER: S-EPMC4263532 | biostudies-literature | 2014

REPOSITORIES: biostudies-literature

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Functionally selective signaling for morphine and fentanyl antinociception and tolerance mediated by the rat periaqueductal gray.

Morgan Michael M MM Reid Rachel A RA Saville Kimber A KA

PloS one 20141211 12

Functionally selective signaling appears to contribute to the variability in mechanisms that underlie tolerance to the antinociceptive effects of opioids. The present study tested this hypothesis by examining the contribution of G protein-coupled receptor kinase (GRK)/Protein kinase C (PKC) and C-Jun N-terminal kinase (JNK) activation on both the expression and development of tolerance to morphine and fentanyl microinjected into the ventrolateral periaqueductal gray of the rat. Microinjection of ...[more]

PMID: 25503060

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Project description:Background: Parkinson’s disease (PD) is a progressive, degenerative disease with early-stage pathology hypothesized to manifest in brainstem regions. Vocal deficits, including soft monotone speech, result in significant clinical and quality of life issues and are present in 90% of PD patients; yet, the underlying pathology mediating these significant voice deficits is unknown. The Pink1-/- rat is a valid model of early-onset PD that presents with analogous vocal communication deficits (e.g. reduced loudness). Previous work shows abnormal α-synuclein protein aggregation in the periaqueductal gray (PAG), a brain region critical and necessary to the modulation of mammalian vocal behavior. In this study, we used high-throughput RNA sequencing to examine gene expression within the PAG of both male and female Pink1-/- rats as compared to age-matched wildtype controls. We used a bioinformatic approach to (1) test the hypothesis that loss of Pink1 in the PAG will influence expression of genes that interact with Pink1, (2) highlight other key genes that relate to Mendelian PD, and (3) catalog molecular targets important for the production of rat vocalizations. Results: Knockout of the Pink1 gene resulted in differentially expressed genes for both male and female rats. Pathway analysis highlighted several significant metabolic pathways. Weighted gene co-expression network analysis (WGCNA) was used to identify gene nodes and their interactions in (A) males, (B) females, and (C) combined-sexes datasets. For each analysis, within the module containing the Pink1 gene, Pink1 itself was the central node with the highest number of interactions with other genes including solute carriers, glutamate metabotropic receptors, and genes associated with protein localization. Strong connections between Pink1 and Krt2 and Hfe were found in both males and female datasets. In females a number of modules were significantly correlated with vocalization traits. Of interest, gene enrichment of the key vocal Cyan module in females showed a significant number of neuromodulatory genes including Nts, Slc6a4, Slc10a4, Ndnf, and Gpr160, that may be responsible for the modulation of rat vocalizations. The top biological pathways within the female Cyan vocal module included the regulation of membrane depolarization, indolalkylamine metabolic process, and monoamine transport. Conclusions: Overall, this work supports the premise that gene expression changes in the PAG may contribute to the vocal behavioral and deficits observed in this PD rat model. Additionally, this dataset identifies genes that represent new therapeutic targets for PD voice disorders.

Dataset Information

Functionally selective signaling for morphine and fentanyl antinociception and tolerance mediated by the rat periaqueductal gray.

Publications

Functionally selective signaling for morphine and fentanyl antinociception and tolerance mediated by the rat periaqueductal gray.

Similar Datasets

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