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Tracking Drug-induced Changes in Receptor Post-internalization Trafficking by Colocalizational Analysis
Published on: July 3, 2015
Agonist-dependent internalization of D2 receptors: Imaging quantification by confocal microscopy
Julian L Goggi1, Alessandro Sardini, Alice Egerton
1MRC Clinical Science Centre, Imperial College Faculty of Medicine, Hammersmith Hospital Campus, London, United Kingdom.
Synapse (New York, N.Y.)
|January 19, 2007
Summary
This study introduces a new method to measure dopamine D2 receptor internalization, crucial for understanding brain imaging results. The technique helps differentiate receptor binding changes from actual receptor internalization.
Area of Science:
- Neuroscience
- Pharmacology
- Biochemistry
Background:
- Positron emission tomography (PET) and SPECT imaging of D2 dopamine (DA) receptors often interpret decreased radiotracer binding potential (BP) as increased synaptic DA competition.
- This interpretation may be confounded by agonist-induced D2 receptor (D2R) internalization, which also reduces radioligand binding availability.
Purpose of the Study:
- To develop and validate a direct method for quantifying D2R internalization in response to agonists.
- To improve the interpretation of D2 radiotracer BP alterations in neuroimaging studies.
Main Methods:
- A confocal microscopy approach using double-labeling with antibodies against intracellular and extracellular D2R epitopes.
- Quantification of D2R internalization by distinguishing extracellular from intracellular staining signals after agonist stimulation.
Main Results:
- Dopamine (DA) and bromocriptine (D2 agonists) significantly increased D2R internalization.
- SKF38393 (a D1 agonist) did not induce D2R internalization.
- D2 antagonist sulpiride and internalization inhibitors (phenylarsine oxide, sucrose) blocked agonist-induced D2R internalization, validating the method.
Conclusions:
- The developed confocal microscopy method provides a direct and streamlined way to assess D2R internalization in vitro.
- This methodology will enhance the understanding of D2R pharmacology and mechanisms, informing the interpretation of in vivo imaging data.
