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Copyright © 1998 by Institute of Pharmacology Polish Academy of Sciences |
Pol. J. Pharmacol., 1998, 50, 425-429 ISSN 1230-6002 |
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Postmortem instability of dopamine and its metabolites in rat striatum and limbic forebrain.
B. KAROLEWICZ, I. ROMAŃSKA, L. ANTKIEWICZ-MICHALUK. Pol. J. Pharmacol., 1998, 50, 425-429. The level of dopamine (DA) and its metabolites 3,4-dihydroxyphenylacetic acid (DOPAC), homovanillic acid (HVA) and 3-methoxytyramine (3-MT) were determined in the brains of rats kept 24 h after death at two different temperatures, 4°C and 22°C. The estimations were carried out in the striatum and limbic forebrain containing: nucleus accumbens, septum, limbic cortex, amygdala, tuberculum olfactorium. Brain tissue of control rats was dissected immediately after decapitation, frozen over solid CO2 and stored at -70°C untill assayed. DA and its metabolites were measured, using high-performance liquid chromatography (HPLC) with electrochemical detection. The levels of DA, DOPAC and HVA in the striatum were significantly decreased (from 50% to 80%) when rats were kept 24 h after death. The changes were more pronounced at 22°C than at 4°C. As the decrease in DA concentration was stronger than that of its final metabolite HVA, the ratio of HVA/DA concentration measured as an index of the rate of DA metabolism was even increased (from 8 to 11). Different changes occurred in the limbic region, where the levels of DA and HVA did not change neither at 4°C nor 22°C. The level of intraneuronally formed DA metabolite - DOPAC was elevated (by about 60%). The level of 3-MT, extraneuronally formed DA metabolite, was significantly increased both in the striatum (200%) and limbic DA structures (500%). These data demonstrate regional postmortal differences in stability of DA and its metabolite levels, which are in the striatum temperature-, time-, and storage-dependent. That implicates a careful assessment of postmortem studies when measuring the neurotransmitter dynamics in human necropsy material. Key words: dopamine metabolism, 3,4-dihydroxyphenylacetic acid (DOPAC), homovanillic acid (HVA), 3-methoxytyramine (3-MT), postmortem studies, high performance liquid chromatography (HPLC) |
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