Postmortem instability of dopamine and its metabolites in rat striatum and limbic forebrain.
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 degrees C and 22 degrees 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 degrees C until 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 degrees C than at 4 degrees 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 degrees C nor 22 degrees 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.
Karolewicz
B
B
Department of Biochemistry, Polish Academy of Sciences, Kraków, Poland.
Romańska
I
I
Antkiewicz-Michaluk
L
L
D015102:3,4-Dihydroxyphenylacetic Acid / Q000378:metabolism; D000818:Animals; D001344:Autopsy; D002851:Chromatography, High Pressure Liquid; D015925:Cryopreservation / Q000379:methods; D004298:Dopamine / Q000378:metabolism*; D004355:Drug Stability; D006719:Homovanillic Acid / Q000378:metabolism; D066298:In Vitro Techniques; D008032:Limbic System / Q000378:metabolism*; D008297:Male; D051381:Rats; D017208:Rats, Wistar; D013997:Time Factors; D014793:Visual Cortex / Q000378:metabolism*
D015102:3,4-Dihydroxyphenylacetic Acid; D004298:Dopamine; D006719:Homovanillic Acid