Hormonal effects of apomorphine in schizophrenia

The hormonal effects of apomorphine, a direct-acting dopamine receptor agonist, in schizophrenic patients are of interest in view of the therapeutic efficacy of dopamine receptor antagonists. In this study, apomorphine (0.75 mg s.c.) and placebo were administered to unmedicated acute and chronic schizophrenics and controls. Apomorphine-induced prolactin suppression did not discriminate between the groups. However, an inverse relationship between basal prolactin levels and the severity of positive symptoms was detected in the patients with acute schizophrenia, consistent with a role for dopamine in the genesis of these symptoms. Growth hormone increments after apomorphine administration were blunted in the chronic schizophrenic patients, particularly those with 'negative' symptoms. It is argued that this blunting is not due to previous neuroleptic therapy and may represent evidence of structural change in the hypothalamus in this group of patients.