Interstitial 3-methoxytyramine reflects striatal dopamine release: an in vivo microdialysis study.
Previous ex vivo studies have provided indirect evidence that the dopamine (DA) metabolite 3-methoxytyramine (3-MT) may be a useful index of DA release in vivo. In the present study, in vivo microdialysis was utilized to assess directly the relationship between extracellular DA and 3-MT in the striatum of rats following a variety of pharmacological manipulations. Apomorphine, a DA receptor agonist, produced a rapid, transient decrease in both DA and 3-MT. Conversely, the DA receptor antagonist haloperidol produced a concomitant increase in extracellular DA and 3-MT. Increases in DA and 3-MT were also noted following the administration of the DA uptake inhibitor, bupropion. Local application of tetrodotoxin resulted in the complete elimination of measurable amounts of DA and 3-MT in the dialysate, gamma-Butyrolactone also greatly decreased DA and 3-MT. Finally, d-amphetamine produced a large increase in DA and 3-MT in animals that had been treated previously with gamma-butyrolactone. The Pearson correlation coefficients for DA and 3-MT following these manipulations ranged from 0.87 to 0.97. These data indicate that interstitial 3-MT is an accurate index of DA release. However, when compared with previous ex vivo findings, the present results also suggest that changes in tissue concentrations of 3-MT may not reliably reflect DA release following certain pharmacological manipulations.
Brown
E E
EE
Department of Psychiatry, University of British Columbia, Vancouver, Canada.
Damsma
G
G
Cumming
P
P
Fibiger
H C
HC
D015102:3,4-Dihydroxyphenylacetic Acid / Q000378:metabolism; D015107:4-Butyrolactone / Q000494:pharmacology; D000818:Animals; D000928:Antidepressive Agents / Q000494:pharmacology; D001058:Apomorphine / Q000494:pharmacology; D016642:Bupropion; D003342:Corpus Striatum / Q000187:drug effects / Q000378:metabolism*; D003956:Dialysis / Q000379:methods; D004298:Dopamine / Q000031:analogs & derivatives / Q000032:analysis / Q000378:metabolism*; D006220:Haloperidol / Q000494:pharmacology; D006719:Homovanillic Acid / Q000378:metabolism; D007700:Kinetics; D008297:Male; D011427:Propiophenones / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D013779:Tetrodotoxin / Q000494:pharmacology
D000928:Antidepressive Agents; D011427:Propiophenones; D016642:Bupropion; D015102:3,4-Dihydroxyphenylacetic Acid; D013779:Tetrodotoxin; D006220:Haloperidol; C001746:3-methoxytyramine; D001058:Apomorphine; D015107:4-Butyrolactone; D004298:Dopamine; D006719:Homovanillic Acid