Low CSF concentrations of cyclic GMP in schizophrenia.

Increasing evidence suggests that the concentrations of cyclic guanosine 3'5'-monophosphate (cGMP) in the cerebrospinal fluid (CSF) may reflect central cholinergic activity. When the concentrations of this nucleotide in the CSF from 28 schizophrenic patients (13 without and 15 with neuroleptic treatment) and 16 psychiatrically healthy controls was determined the schizophrenics showed significantly lower CSF levels of cGMP as compared to controls. As dopamine and homovanillic acid concentrations were not altered in these CSF samples, this finding of reduced cGMP suggests a cholinergic-dopaminergic imbalance in schizophrenia, with a reduction of the former and consequently a relative dominance of the latter.