APOMORPHINE STIMULATION OF VASOPRESSIN-NEUROPHYSINS AND OXYTOCIN-NEUROPHYSINS - EVIDENCE FOR INCREASED OXYTOCINERGIC AND DECREASED VASOPRESSINERGIC FUNCTION IN SCHIZOPHRENICS

Apomorphine challenge tests (0.5 mg SC) were performed in 14 normal male volunteers and in 9 male schizophrenic inpatients, drug-free for at least 2 wk. In the normal volunteers, apomorphine induced an increase of serum growth hormone (GH) (maximum at 40 min), of vasopressin-neurophysin (hN(P)I) (maximum at 20 min), and oxytocin-neurophysin (hN(P)II) (maximum at 20 min). The release of neurophysins was independent of digestive side effects. In the schizophrenics, the GH level and release pattern were similar to those in the controls. The basal level of hN(P)I was reduced (t0: 0.42+/-0.1 ng/ml in the schizophrenics and 0.66+/-0.05 ng/ml in the controls, p<0.02). In contrast, the basal level of hN(P)II was increased (3.34+/-0.04 ng/ml in the schizophrenics to 0.92+/-0.21 ng/ml in the controls, p=0.001). The response to apomorphine was blunted, with no significant release of hN(P)I or of hN(P)II. Although the hN(P)II data are consistent with an increased dopaminergic tone, the psychopathological meaning of the increased basal oxytocinergic and decreased vasopressinergic functions remains to be defined.