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Dopamine D3-preferring ligands act at synthesis modulating autoreceptors
C W Aretha1, A Sinha, M P Galloway
1Department of Psychiatry and Behavioral Neurosciences, Wayne State University School of Medicine, Detroit, Michigan, USA.
The Journal of Pharmacology and Experimental Therapeutics
|August 1, 1995
Summary
Dopamine D3 receptor ligands, (+/-)7-OH DPAT, (+)-UH232, and (+)-AJ76, were tested for presynaptic autoreceptor activity. (+/-)7-OH DPAT acts as a D3 autoreceptor agonist, particularly in the olfactory tubercle.
Area of Science:
- Neuropharmacology
- Dopamine Receptor Research
Background:
- Dopamine D3 receptors exhibit distinct binding preferences over D2 receptors.
- Emerging evidence suggests a role for dopamine D3 receptors as autoreceptors.
Purpose of the Study:
- To investigate the presynaptic autoreceptor activity of D3-preferring ligands: (+/-)7-OH DPAT, (+)-UH232, and (+)-AJ76.
- To compare the effects of these ligands across different brain regions with varying D3 receptor densities.
Main Methods:
- Utilized the in vivo gamma-butyro-lactone model to assess dopamine synthesis modulation.
- Examined presynaptic effects in the striatum, nucleus accumbens, and olfactory tubercles.
- Administered D3-preferring ligands and analyzed their agonist and antagonist properties.
Main Results:
- (+/-)7-OH DPAT demonstrated agonist activity at synthesis-modulating dopamine autoreceptors.
- (+/-)7-OH DPAT showed greater potency in the olfactory tubercle (ED50 = 10.2 µg/kg) compared to the striatum (31.8 µg/kg) and nucleus accumbens (38.1 µg/kg).
- (+)-UH232 and (+)-AJ76 antagonized (+/-)7-OH DPAT's effects, with less antagonism observed in the olfactory tubercle.
Conclusions:
- The findings support the hypothesis that dopamine D3 receptors function as autoreceptors.
- (+/-)7-OH DPAT appears to preferentially exert its autoreceptor effects via dopamine D3 receptors, especially in regions with higher D3 receptor abundance like the olfactory tubercle.