Brain gamma-aminobutyrate transaminase and monoamine oxidase activities in suicide victims.

The activity of gamma-aminobutyrate amino-transferase (GABA-T) and monoamine oxidase (MAO-A and -B) was measured in 42 postmortem human brains. Three brain regions (frontal cortex, cingulate cortex and hypothalamus) from 23 controls without known neurological or psychiatric disorder and from 19 suicide victims were analysed. The suicide victims were classified according to the use of violent and non-violent methods and to the presence or absence of a known history of depressive disorder. No difference was found between the series of suicide victims and the control subjects with regard to GABA-T activity. Carbon monoxide poisoning and death by drug overdose, however, were found to reduce the activity. The MAO-B activity did not differ between the groups. With MAO-A, however, a significant elevation (t = 2.01; P less than 0.05) was found in the hypothalamic region of the suicide victims. The difference seemed to be confined to the subgroup of suicides with a record of depressive disorder.