Phasic alterations in dopamine metabolites following continuous administration of amphetamine.

Rats were treated with slow-release (+)-amphetamine pellets for 7 days and then sacrificed at various times following pellet removal. Pellet-treated animals had decreased dopamine levels in caudate but not nucleus accumbens, with no recovery even 30 days after pellet removal. In both caudate and accumbens the levels of 3,4-dihydroxyphenylacetic acid and homovanillic acid were decreased at the time of pellet removal, then increased shortly after pellet removal, and were again decreased at 10 and 30 days after pellet removal. These fluctuations may reflect cyclical alterations in dopamine receptors following continuous amphetamine.