Peripheral indices of dopamine and serotonin in schizophrenia

Abstract

PRL, and cortisol in normal humans, possibly via a 5-HT2c receptor mechanism. This study investigated the effects of MK-212 on plasma PRL, cortisol, and temperature response in neuroleptic-free schizophrenic patients (60 males, 12 females) and normal controls (32 males, 11 females). The PRL and temperature, but not the cortisol responses to MK212, were significantly blunted in male but not female schizophrenic patients. MK-212 made normals more restless, feel less good overall and strange. These effects were blunted in schizophrenics. There was no difference in the PRL, cortisol or temperature responses between neuroleptic resistant and responsive schizophrenic patients. The PRL and cortisol responses to MK-212 were significantly correlated. The hormone and temperature responses were not correlated with baseline psychopathology. The cortisol and PRL responses in male schizophrenic patients were also positively correlated with ventricular brain ratio and prefrontal sulcal prominence, respectively. The MK-212-induced PRL response was negatively correlated with plasma homovanillic acid (HVA) levels. Clozapine treatment blocked the hormone and temperature responses to MK-212. Improvement in positive and negative symptoms after 6 weeks of clozapine treatment was negatively correlated with the hormone responses to MK-212 in male schizophrenic patients. Further studies are needed to determine the etiology and significance of the diminished response of 5HT2c receptors to serotonergic challenges in schizophrenia.