Apomorphine lowers dopamine synthesis for up to 48 h: implications for drug sensitization.
Previous reports have shown that tolerance or sensitization to apomorphine depends on the dosage interval. The effect of apomorphine on behaviour increases when there is a drug-free period between successive injections. Here we studied the biochemical action of apomorphine during a drug-free period. The experiments showed that dopamine level and dopamine turn-over are persistently inhibited for at least 48 h after apomorphine administration. At 24 h after drug injection, there was a decrease of both DOPAC level and tyrosine hydroxylase activity. The results suggest that apomorphine induces long-lasting dopaminergic inhibition action that increases drug-induced behavioural response, perhaps after development of postsynaptic hypersensitivity.
Department of Physiology, School of Medicine, University of La Laguna, Tenerife, Canary Islands, Spain.
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M
Rodriguez
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R
Castro
D015102:3,4-Dihydroxyphenylacetic Acid / Q000378:metabolism; D000704:Analysis of Variance; D000818:Animals; D001058:Apomorphine / Q000008:administration & dosage / Q000494:pharmacology*; D002851:Chromatography, High Pressure Liquid; D003342:Corpus Striatum / Q000187:drug effects / Q000378:metabolism*; D004298:Dopamine / Q000096:biosynthesis*; D004334:Drug Administration Schedule; D007980:Levodopa / Q000378:metabolism; D009043:Motor Activity / Q000187:drug effects*; D051381:Rats; D011919:Rats, Inbred Strains; D012016:Reference Values; D013997:Time Factors; D014446:Tyrosine 3-Monooxygenase / Q000378:metabolism
D015102:3,4-Dihydroxyphenylacetic Acid; D007980:Levodopa; D014446:Tyrosine 3-Monooxygenase; D001058:Apomorphine; D004298:Dopamine