Absence of a difference in the neurosecretory activity of supraoptic nucleus vasopressin neurons of neuroleptic-treated schizophrenic patients.

Dysfunction in water intake and metabolism has frequently been reported in schizophrenia. The general population of schizophrenics under neuroleptic treatment secretes lower amounts of vasopressin than controls at comparable values of plasma osmolality. The purpose of the present study was to investigate the synthetic activity of vasopressin neurons of the dorsolateral supraoptic nucleus in schizophrenia on postmortem material using a battery of histochemical activity markers. Our material consisted of formalin-fixed and paraffin-embedded hypothalami from 5 schizophrenic patients under neuroleptic treatment and from 5 matched controls, obtained from The Netherlands' Brain Bank. DSM-III or DSM-IV criteria were used for the clinical diagnosis. The histochemical markers used to study the neuronal activity of the magnocellular vasopressin-synthesizing neurons were: cell size, size of the Golgi apparatus, and expression of vasopressin and tyrosine hydroxylase mRNA by in situ hybridization. Morphometric evaluation and statistical analysis (Mann-Whitney U test) were performed. Our results showed no statistically significant differences in any of the neuronal activity markers between schizophrenic patients and controls. Therefore, the neurosecretory activity of vasopressin neurons of the dorsolateral part of the supraoptic nucleus does not appear to be changed in schizophrenic patients under medication. Since our sample did not include patients with reported polydipsia or hyponatremia, prospective investigation is needed to evaluate the above-mentioned neuronal activity markers in such a particular subgroup of schizophrenic patients.