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fwiw - found the 2nd abstract again...

Posted by michael on March 23, 2001, at 0:16:10

In reply to Thanks Andrew (np), posted by michael on March 22, 2001, at 23:55:08

Eur J Pharmacol 1991 Jul 23;200(1):65-72 Related Articles, Books


Pramipexole, a dopamine D2 autoreceptor agonist, decreases the extracellular concentration of dopamine in vivo.

Carter AJ, Muller RE

Department of Pharmacology, Boehringer Ingelheim KG, Ingelheim, F.R.G.

Pramipexole (SND 919) is a dopamine D2 autoreceptor agonist which is structurally related to talipexole (B-HT 920), a potential antipsychotic agent. The aim of this study was to investigate the effects of pramipexole on the extracellular concentration of dopamine in vivo. Dopamine and its metabolites, 3,4-dihydrophenylacetic acid and homovanillic acid, were measured in the anterior striatum of freely moving rats by microdialysis and high-performance liquid chromatography with electrochemical detection. Pramipexole (30 and 100 micrograms/kg) caused long-lasting decreases in the extracellular concentrations of dopamine and its metabolites. Talipexole (30 micrograms/kg) produced similar effects. Sulpiride (5 mg/kg), a selective dopamine D2 antagonist, caused a transient increase in the concentration of dopamine and long-lasting increases in the concentrations of its metabolites; it also reversed the effects of pramipexole. SCH-23390 (100 micrograms/kg), a selective dopamine D1 receptor antagonist, caused a transient increase in the concentration of dopamine but did not affect the concentrations of the metabolites. SCH-23390 failed to reverse the effects of pramipexole. These results indicate that pramipexole reduces the extracellular concentrations of dopamine and its metabolites in vivo through a reversible interaction with the dopamine D2 receptor.

PMID: 1685123


> Michael,
> >
> > It to be expected that at low doses Pramipexole acts as an antipsychotic and an AD at higher doses, just as the inverse is true of amisulpride. The dosages recommended for its use as an AD (i.e. 5mg./day) are high doses and it definatley doesn't act as an antipsych. at those doses.
> >
> > Just one note, the presynaptic autoreceptors have a stronger binding affinity than the postsynaptic, but they get filled up with rather small does of a D2/D3 meds. That is why at low doses amisulpride and pramipexole latch onto the autoreceptors but at higher doses those receptors are full and the meds then start hitting the postsynaptic receptors.
> >
> > AndrewB


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poster:michael thread:57230
URL: http://www.dr-bob.org/babble/20010319/msgs/57240.html