01 August 2010
Long-term adaptation to high doses of morphine causes desensitization of micro-OR- and delta-OR-stimulated G-protein response in forebrain cortex but does not decrease the amount of G-protein alpha subunits
Lenka BourovaBCDE, Miroslava VosahlikovaBD, Dmytro KaganB, Katerina DlouhaBD, Jiri NovotnyBF, Petr SvobodaACDEFGMed Sci Monit 2010; 16(8): BR260-270 :: ID: 881099
Abstract
Background: The functional activity of trimeric guanine-nucleotide-binding proteins (G-proteins) represents an essential step in linking and regulation of the opioid receptor (micro-,delta- and kappa-OR)-initiated signaling pathways. Theoretical basis and/or molecular mechanism(s) of opioid tolerance and addiction proceeding in the central nervous system were not studied in the forebrain cortex of mammals with respect to quantitative analysis of opioid-stimulated trimeric G-protein activity.
Material/Methods: G-protein activity was measured in PercollR-purified plasma membranes (PM) isolated from the frontal brain cortex of control and morphine-treated rats by both high-affinity [32P]GTPase and [35S]GTPgammaS binding assays. Exposition to morphine was performed by intra-muscular application of this drug. Control animals were injected with sterile PBS.
Results: Both micro-OR (DAMGO)- and delta-OR (DADLE)-responses were clearly desensitized in PM isolated from morphine-treated rats; kappa-OR (U-69593)- and baclofen (GABAB-R)-stimulated [35S]GTPgammaS binding was unchanged, indicating the specificity of the morphine effect. Under such conditions, the amount of G-protein alpha subunits was unchanged. The order of efficacy DADLE>DAMGO>U-69593 was the same in control and morphine-treated PM. Behavioral tests indicated that morphine-treated animals were fully drug-dependent and developed tolerance to subsequent drug addition.
Conclusions: Prolonged exposure of rats to high doses of morphine results in decrease of the over-all output of OR-stimulated G-protein activity in the forebrain cortex but does not decrease the amount of these regulatory proteins. These data support the view that the mechanism of the long-term adaptation to high doses of morphine is primarily based on desensitization of OR-response preferentially oriented to micro-OR and delta-OR.
Keywords: Morphine - pharmacology, Guanosine Diphosphate - metabolism, Guanosine 5'-O-(3-Thiotriphosphate) - metabolism, GTP-Binding Protein alpha Subunits - metabolism, Enkephalin, Ala(2)-MePhe(4)-Gly(5)- - pharmacology, Drug Tolerance, Dose-Response Relationship, Drug, Cerebral Cortex - metabolism, Cell Membrane - enzymology, Behavior, Animal - drug effects, Baclofen - pharmacology, Adaptation, Physiological - drug effects, Rats, Wistar, Receptors, Opioid, delta - metabolism, Receptors, Opioid, mu - metabolism, Substance Withdrawal Syndrome - physiopathology, Time Factors
Editorial
01 April 2024 : Editorial
Editorial: Forty Years of Waiting for Prevention and Cure of HIV Infection – Ongoing Challenges and Hopes for Vaccine Development and Overcoming Antiretroviral Drug ResistanceDOI: 10.12659/MSM.944600
Med Sci Monit 2024; 30:e944600
In Press
05 Mar 2024 : Clinical Research
Role of Critical Shoulder Angle in Degenerative Type Rotator Cuff Tears: A Turkish Cohort StudyMed Sci Monit In Press; DOI: 10.12659/MSM.943703
06 Mar 2024 : Clinical Research
Comparison of Outcomes between Single-Level and Double-Level Corpectomy in Thoracolumbar Reconstruction: A ...Med Sci Monit In Press; DOI: 10.12659/MSM.943797
21 Mar 2024 : Meta-Analysis
Economic Evaluation of COVID-19 Screening Tests and Surveillance Strategies in Low-Income, Middle-Income, a...Med Sci Monit In Press; DOI: 10.12659/MSM.943863
10 Apr 2024 : Clinical Research
Predicting Acute Cardiovascular Complications in COVID-19: Insights from a Specialized Cardiac Referral Dep...Med Sci Monit In Press; DOI: 10.12659/MSM.942612
Most Viewed Current Articles
17 Jan 2024 : Review article
Vaccination Guidelines for Pregnant Women: Addressing COVID-19 and the Omicron VariantDOI :10.12659/MSM.942799
Med Sci Monit 2024; 30:e942799
14 Dec 2022 : Clinical Research
Prevalence and Variability of Allergen-Specific Immunoglobulin E in Patients with Elevated Tryptase LevelsDOI :10.12659/MSM.937990
Med Sci Monit 2022; 28:e937990
16 May 2023 : Clinical Research
Electrophysiological Testing for an Auditory Processing Disorder and Reading Performance in 54 School Stude...DOI :10.12659/MSM.940387
Med Sci Monit 2023; 29:e940387
01 Jan 2022 : Editorial
Editorial: Current Status of Oral Antiviral Drug Treatments for SARS-CoV-2 Infection in Non-Hospitalized Pa...DOI :10.12659/MSM.935952
Med Sci Monit 2022; 28:e935952