No association between polymorphisms in the serotonin transporter gene and susceptibility to cocaine dependence among African-American individuals

Genetic research of cocaine abuse has been relatively limited among the African-American population. Since the serotonin transporter (5HTT) may be involved in modulating effects of cocaine, we investigated whether allelic variants of the 5HTT gene may confer susceptibility to cocaine dependence among African-American individuals. One hundred and fifty-six cocaine-dependent subjects and 82 controls were studied. Polymerase chain reaction-based genotyping of a variable-number-tandem-repeat (VNTR) marker yielded three alleles designated 12, 10 and 9. Genotype and allele frequencies were compared using chi-square analyses. We found no differences between subjects and controls with respect to genotype distribution (cocaine: 12/12 = 50%, 10/12 = 35.3%, 10/10 = 13.5%, 9/12 = 1.3%; controls: 12/12 = 42.7%, 10/12 = 39.0%, 10/10 = 17.1%, 9/12 = 1.2%). Similarly, allele frequencies of the VNTR marker did not differ between the two groups (cocaine: 12 = 68.3%, 10 = 31.1%, 9 = 0.6%; controls: 12 = 62.8%, 10 = 36.6%, 9 = 0.6%). Our findings do not seem to support a relationship between VNTR polymorphisms and cocaine dependence among African-American patients. Further studies involving larger samples are required to confirm our results

Serotonin transporter polymorphisms and measures of impulsivity, aggression, and sensation seeking among African-American cocaine-dependent individuals

Considerable evidence indicates that serotonergic mechanisms, particularly the serotonin transporter (5HTT), may mediate central effects of cocaine and may also be involved in impulsive and aggressive behavior. We investigated whether polymorphisms in the 5HTT gene were related to traits of impulsivity, sensation seeking, and aggression among cocaine abusers. Standardized measures of these personality traits were obtained in a sample of 105 severely affected cocaine-dependent African-American subjects and 44 African-American controls. Two polymorphisms of the 5HTT gene were examined involving the 5' promoter (5HTTLPR) region and a 17 base pair variable-number-tandem-repeat (VNTR) marker among cocaine patients. No significant relationships were observed between polymorphic variants of the 5HTTLPR and VNTR regions and scores on any of the trait measures. Similarly, demographic variables and measures of severity of substance use and depression were unrelated to allele frequencies or genotype distributions of the variants among cocaine patients. As expected, cocaine patients scored significantly higher on total scores of impulsivity, aggression, and sensation seeking compared to controls. The findings do not seem to support an association between these polymorphisms in the 5HTT gene and impulsive-aggressive traits among cocaine-dependent African-American individuals