Cyclic GMP in the CSF of patients with schizophrenia before and after neuroleptic treatment

Cerebrospinal fluid (CSF) cyclic GMP may derive from central cholinergic neurotransmission. Measurement of CSF cyclic GMP may allow evaluation of possible implications of the dopaminergic hyperactivity in schizophrenia proposed by the dopamine hypothesis. The CSF cyclic GMP levels in 27 drug-free schizophrenic patients was measured and compared to that in 9 psychiatrically-healthy individuals. The mean CSF cyclic GMP level of the schizophrenic patients was 23% lower than that of the control group, but this difference, did not attain statistical significance. In addition the CSF cyclic GMP levels in a group of 10 schizophrenic patients were compared before and after 2 months of neuroleptic treatment. The mean level of cyclic GMP rose 50% after treatment with phenothiazines (P<0.05). These results could indicate some tendency for decreased activity of central cholinergic neurons in schizophrenia as well as a restored dopaminergic-cholinergic balance after neuroleptic treatment.