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Regional differences in cannabinoid receptor/G-protein coupling in rat brain
C S Breivogel1, L J Sim, S R Childers
1Department of Physiology and Pharmacology, and Center for Investigative Neuroscience, Bowman Gray School of Medicine, Wake Forest University, Winston-Salem, North Carolina 27157, USA.
The Journal of Pharmacology and Experimental Therapeutics
|October 8, 1997
Summary
Cannabinoid receptor G-protein activation varies across rat brain regions. Amplification factors, measuring G-proteins per receptor, differ significantly, indicating environment-dependent coupling.
Area of Science:
- Neuroscience
- Pharmacology
- Molecular Biology
Background:
- Cannabinoid receptor activation initiates intracellular signaling via G-protein coupling.
- Quantifying receptor/transducer amplification factors reveals the efficiency of G-protein activation per occupied receptor.
Purpose of the Study:
- To investigate regional differences in amplification factors for cannabinoid receptors in the rat brain.
- To determine if the cellular environment influences cannabinoid receptor G-protein coupling.
Main Methods:
- Autoradiography using [3H]WIN 55212-2 and WIN 55212-2-stimulated [35S]GTPgammaS binding.
- Saturation binding analysis of [3H]SR141716A (antagonist) and [3H]WIN 55212-2 (agonist) binding to quantify amplification factors.
- Assay of net agonist-stimulated [35S]GTPgammaS binding.
Main Results:
- Significant variations in amplification factors were observed across brain regions, ranging from 2.0 (frontal cortex) to 7.5 (hypothalamus) for [3H]SR141716A binding.
- Amplification factors for [3H]WIN 55212-2 binding ranged from 2.4 (hippocampus) to 5.5 (thalamus).
- Differences in receptor binding and G-protein activation ratios were noted among brain regions, suggesting environment-dependent coupling.
Conclusions:
- Cannabinoid receptor G-protein coupling efficiency is not uniform across the rat brain.
- The cellular environment plays a crucial role in modulating cannabinoid receptor-mediated G-protein activation.