Brain regional α-[11C]Methyl-L-Tryptophan trapping in impulsive subjects with borderline personality disorder

Objective: Neurotransmission of serotonin (or 5-hydroxytryptamine [5-HT]) is thought to be disturbed in patients exhibiting impulsive behaviors. However, until recently it has not been possible to test this hypothesis in the brains of living humans. Method: Unidirectional trapping of the 5-HT precursor analog alpha-[C-11]methyl-L-tryptophan (alpha-[C-11]MTrp) has been proposed as an index of 5-HT synthesis capacity. The authors measured brain regional alpha-[C-11]MTrp trapping with positron emission tomography in medication-free subjects with borderline personality disorder (N=13) and a healthy comparison group (N=11). Impulsivity was assessed by using a laboratory measure of behavioral disinhibition, go/no-go commission errors. Results: Compared to healthy men, the men with borderline personality disorder had significantly lower alpha-[C-11]MTrp trapping in corticostriatal sites, including the medial frontal gyrus, anterior cingulate gyrus, superior temporal gyrus, and corpus striatum. In the women with borderline personality disorder, significantly lower (alpha[C-11]MTrp trapping was seen in fewer regions, but in both men and women, negative correlations with impulsivity scores were identified in the medial frontal gyrus, anterior cingulate gyrus, temporal gyrus, and striatum. Conclusions: Low 5-HT synthesis capacity in corticostriatal pathways may contribute to the development of impulsive behaviors in persons with borderline personality disorder.