Comparison of effects of D-1 and D-2 dopamine receptor agonists on neurons in the rat caudate putamen: an electrophysiological study.
Extracellular single-unit recording and microiontophoretic techniques were used to characterize the pharmacological properties of dopamine (DA) receptor subtypes within the rat caudate putamen (CPu), a striatal structure that receives a dense innervation from DA neurons originating from the substantia nigra pars compacta (A9 DA neurons). Similar to the action of DA, the DA D-1 receptor agonist (+)SKF-38393 generally potentiated the activation produced by glutamate (GLU) at low ejection currents (less than or equal to 5 nA); at higher ejection currents, it depressed 97% of the CPu neurons tested. By contrast, the D-2 receptor agonist LY-171555 (quinpirole) was much less effective in affecting the firing rate of CPu cells. The selective D-1 antagonist SCH-23390, administered either intravenously or iontophoretically, completely blocked the (+)SKF-38393-induced effects on CPu cells but failed to change the depressant effects produced by either quinpirole or 5-HT. On the other hand, the selective D-2 antagonist I-sulpiride, blocked the effects induced by quinpirole but not (+)SKF-38393. These observations suggest that the D-1 and D-2 DA receptor agonists elicit their effects via distinct DA receptor subtypes. A comparison of these results with our previous results obtained from the nucleus accumbens (NAc) indicates that NAc cells are more responsive to DA D-2 agonist, whereas CPu cells are more sensitive to D-1 agonist. Therefore, D-1 receptors in the CPu may have a critical role in mediating the effect produced by DA.(ABSTRACT TRUNCATED AT 400 WORDS)
Hu
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Department of Psychiatry and Behavioral Sciences, State University of New York, Stony Brook 11794.
Wang
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D015647:2,3,4,5-Tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-benzazepine; D000818:Animals; D001552:Benzazepines / Q000494:pharmacology; D002421:Caudate Nucleus / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D004298:Dopamine / Q000494:pharmacology; D004873:Ergolines / Q000494:pharmacology; D007275:Injections, Intravenous; D007478:Iontophoresis; D008297:Male; D009433:Neural Inhibition; D009474:Neurons / Q000187:drug effects / Q000502:physiology*; D009714:Nucleus Accumbens / Q000166:cytology / Q000187:drug effects; D011699:Putamen / Q000166:cytology / Q000502:physiology*; D019257:Quinpirole; D051381:Rats; D011919:Rats, Inbred Strains; D011954:Receptors, Dopamine / Q000502:physiology*; D017447:Receptors, Dopamine D1; D017448:Receptors, Dopamine D2
D001552:Benzazepines; D004873:Ergolines; D011954:Receptors, Dopamine; D017447:Receptors, Dopamine D1; D017448:Receptors, Dopamine D2; D019257:Quinpirole; D015647:2,3,4,5-Tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-benzazepine; D004298:Dopamine