Calcium dependency and tetrodotoxin sensitivity of neostriatal dopamine release in 5-day-old and adult rats as measured by in vivo microdialysis.
The calcium dependency and tetrodotoxin sensitivity of extracellular dopamine levels were assessed by microdialysis in the neostriatum of 5-day-old rat pups and were compared with those obtained in adult rats. The removal of calcium from the dialysate reduced spontaneous levels of extracellular dopamine to 20% of normal in the 5-day-old pups and to 10% of normal in the adults. Calcium-free dialysate also decreased potassium-evoked dopamine release to approximately 20% of baseline in both ages. Furthermore, the addition of tetrodotoxin to the dialysate decreased spontaneous levels of extracellular dopamine to 10% of baseline in both ages. The effects of calcium removal and the addition of tetrodotoxin on extracellular levels of the dopamine metabolite 3,4-dihydroxyphenylacetic acid were less pronounced. The results of this study demonstrate that extracellular levels of dopamine sampled by microdialysis in rats as young as 5 days of age are both calcium dependent and tetrodotoxin sensitive; thus, they are derived from neuronal activity and not from injury caused by acute implantation of the probe. Other age-related differences support the hypothesis that dopamine release and turnover is greater in immature rats and may represent a form of compensation for incomplete dopamine nerve terminal ingrowth.
Gazzara
R A
RA
Department of Psychology, State University of New York at Binghamton, New York.
Andersen
S L
SL
D015102:3,4-Dihydroxyphenylacetic Acid / Q000378:metabolism; D000375:Aging / Q000502:physiology*; D000818:Animals; D000831:Animals, Newborn; D002118:Calcium / Q000494:pharmacology*; D004298:Dopamine / Q000378:metabolism*; D007700:Kinetics; D017551:Microdialysis / Q000379:methods; D017072:Neostriatum / Q000187:drug effects / Q000254:growth & development / Q000378:metabolism*; D011188:Potassium / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D013779:Tetrodotoxin / Q000494:pharmacology*; D013997:Time Factors
D015102:3,4-Dihydroxyphenylacetic Acid; D013779:Tetrodotoxin; D011188:Potassium; D002118:Calcium; D004298:Dopamine