Fewer pigmented locus coeruleus neurons in suicide victims: preliminary results

Studies of the noradrenergic system in suicide victims have found evidence of alterations in cortical beta- and alpha-adrenergic receptor binding. Since these receptor changes may be secondary to altered noradrenergic input, we sought to determine whether the pigmented neurons of the locus coeruleus (LC), which provide the noradrenergic innervation to the cerebral cortex, are altered in suicide victims. We studied 11 controls without known psychiatric or neurologic disorders and six suicide victims. LC neuron number, LC volume, and neuron density were determined by computer-assisted mapping. The suicide group had 23% fewer LC neurons and a 38% lower density of LC neurons than controls. The reduction in neuron number was localized to the rostral two thirds of the LC. Neither the LC length nor the LC volume in suicide victims differed from controls. Altered brain noradrenergic neurotransmission in suicide victims may be due to fewer noradrenergic neurons in the LC. Further studies are needed to determine whether this noradrenergic neuron loss is associated with an underlying major depression or specifically with suicidal behavior.