Antipsychotic effects of caerulein, a decapeptide chemically related to cholecystokinin octapeptide, on schizophrenia.

Caerulein, a decapeptide chemically related to CCK-8, was administered intramuscularly to 20 patients with chronic schizophrenia in two different doses of 0.3 and 0.6 microgram/kg. BPRS ratings were made before and 3 weeks after the injection. The neuroleptic therapy was not discontinued, but both drug and dose were not changed at least 3 weeks before the first injection and during the study period. Clinically obvious and statistically significant improvement in psychotic symptoms occurred shortly after the injection of caerulein. The greatest change occurred 1--2 weeks later. There was an evident correlation between the observed changes and the dose injected. Our findings suggest that caerulein has a long-acting, antipsychotic activity in chronic schizophrenia. Furthermore, our findings suggest the involvement of CCK-like peptides in the pathogenesis of schizophrenia.