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Behavioral and neurochemical data suggest functional differences between dopamine D2 and D3 receptors
K Svensson1, A Carlsson, R M Huff
1Department of Pharmacology, University of Göteborg, Sweden.
European Journal of Pharmacology
|October 3, 1994
Summary
Dopamine D3 receptor agonists, like R-(+)-7-OH-DPAT, effectively reduce rat locomotion without impacting dopamine synthesis or release. This suggests the dopamine D3 receptor plays an inhibitory role in locomotion.
Area of Science:
- Neuroscience
- Pharmacology
- Cell Biology
Background:
- Dopamine receptors, particularly D2 and D3 subtypes, are crucial in regulating motor activity.
- Understanding the specific roles of D2 and D3 receptors in locomotion is essential for developing targeted therapies.
Purpose of the Study:
- To investigate the in vitro and in vivo effects of various dopamine receptor agonists on D2 and D3 receptor activity.
- To determine the role of dopamine D3 receptors in regulating rat locomotor activity and dopamine neurotransmission.
Main Methods:
- In vitro assays using Chinese hamster ovary (CHO) cells expressing rat dopamine D2 or D3 receptors to determine agonist potency (EC50 values).
- In vivo locomotor activity experiments in rats treated with dopamine agonists.
- Measurement of brain dopamine synthesis (DOPA accumulation) and release (in vivo microdialysis) in rats.
Main Results:
- Agonists showed varying affinities for D2 and D3 receptors in vitro, with R-(+)-7-OH-DPAT and pramipexole exhibiting higher D3 selectivity.
- R-(+)-7-OH-DPAT and pramipexole significantly reduced rat locomotion at doses that did not alter dopamine synthesis or release.
- Apomorphine, (+)-3-PPP, and quinpirole reduced locomotion at doses that correlated with decreased dopamine release and synthesis.
Conclusions:
- The findings support the hypothesis that functional dopamine D3 receptors are postsynaptic and exert an inhibitory influence on rat locomotion.
- Dopamine D3 receptor agonists may offer a therapeutic strategy for modulating motor activity with potentially fewer central dopaminergic side effects.