Critical evaluation of the postmortem factors influencing neurochemical analyses of brain autopsies.

Abstract

The effect of autolysis in both human and animal brain material was studied experimentally stored at different conditions. Four cell injury enzymes: acid proteinase, acid phosphatase, β-glucuronidase and leucine aminopeptidase; four neurotransmitter synthesizing and metabolizing enzymes: tyrosine hydroxylase (TH), dopa decarboxylase (DDC), glutamic acid decarboxylase (GAD), acetylcholinesterase (AChE) and the concentration of one neurotransmitter, gamma-aminobutyric acid (GABA), were studied. The results of the cell injury enzyme analysis showed that after 3 months of preservation (−20°C) the specific activity of acid proteinase increased four-to five fold in human material. In bovine brains the increase was two times higher after 3 months of storage. The activity of acid phosphatase showed contradictory results, in the human material the activity increased slightly, while in the bovine brains it decreased. The activity of β-glucuronidase remained stable while the activity of leucine aminopeptidase showed some variation during storage. In the case of neurotransmitter metabolizing enzymes analyzed from animal brains, the activity of TH and DDC decreased statistically significantly after 2 days’storage. The same was the case with the activity of GAD after 3 days’storage at +4°C, while the activity of AChE remained unchanged during 3 days’storage. The content of GABA seemed to increase during the first hours of storage, then remaining relatively stable. In the human material analyzed, the activity of TH and DDC did not correlate with the length of storage time because it was relatively short, an average of 2 days. The activity of GAD and AChE and the content of GABA showed a negative correlation with the length of storage time.