Tyrosine hydroxylase immunoreactivity in the locus coeruleus is elevated in violent suicidal depressive patients

Our postmortem study aimed to determine the impact of suicide on the number of noradrenergic neurons of the locus coeruleus (LC) in suicidal depressive patients. Noradrenergic neurons were shown by immunostaining tyrosine hydroxylase in the LC of 22 non-elderly patients with mood disorders compared to 21 age- and sex-matched normal controls. Eleven patients were suicide victims and the other eleven died of natural causes. Seven violent suicide victims revealed an increased number of tyrosine hydroxylase immunoreactive (TH-ir) neurons compared with non-violent suicide victims and controls. No difference was found between the number of TH-ir neurons in all suicidal patients and controls and between non-suicidal patients and controls. The differences of TH-immunoreactivity could neither be attributed to medication nor to the polarity of depressive disorder (unipolar/bipolar). The numbers of TH-ir neurons in suicidal patients correlated negatively with the mean doses of antidepressants. The study suggested a presynaptic noradrenergic dysregulation in the LC related to the level of self-aggression. Traditional antidepressants may, therefore, regulate noradrenergic activity of the LC in suicide patients, however, without demonstrating the suicide-preventing effect.