CHRM1 and schizophrenia: The initial neuroimaging study of CHRMs in schizophrenia used 123I-IQNB SPECT to show there were lower levels of CHRM1/CHRM4 (30% in the striatum and 20% in frontal and temporal regions) in the CNS of drug-free people with the disorder compared to matched control subjects (Raedler et al., 2003).