Dopamine D4 receptor variants in unrelated schizophrenic cases and controls.

The D4 dopamine receptor (D4DR) exists in multiple allelic forms (Van Tol et al.: Nature 358:149-152, 1992) which involve different numbers of a 48 basepair repeat sequence in the putative third cytoplasmic loop. Different binding properties have been reported for at least three of the alleles in cDNA binding assays with clozapine, an atypical neuroleptic, and spiperone (Van Tol et al., 1992). We have examined 115 unrelated schizophrenic cases defined by DSM-III-R criteria and 115 controls of similar ethnicity to determine the frequency of seven different D4 alleles in these groups. No statistically significant difference in the distribution of the alleles existed between cases and controls, although a trend towards a greater prevalence of homozygotes for the 4-repeat allele was observed in schizophrenics.