Serotonergic Studies in Patients With Affective and Personality Disorders

Previous neuroimaging studies of major depression have not controlled for the presence of personality disorders characterized by impulsive aggressive behavior, such as borderline personality disorder (BPD). Using positron emission tomography (PET), we studied regional glucose uptake in response to fenfluramine (FEN) in depressed subjects with BPD (n ¼ 11) and depressed patients without Cluster B Axis II disorders (n ¼ 8). Subjects were scanned while medication-free after a single blind placebo administration and after FEN on a second day. Brain responses were measured by PET imaging of [ 18 F]fluorodeoxyglucose (FDG) and serial prolactin levels. Scans were compared at a voxel level using statistical parametric mapping. Correlations of changes in relative regional cerebral uptake (rCMRglu) with clinical measures were assessed. Depressed borderline patients had greater relative activity in parietotemporal cortical regions (BA 40, BA 22, and BA 42) before and after FEN activation compared to those without BPD. They also had less relative uptake in the anterior cingulate cortex (BA 32) at baseline compared to depressed patients without BPD and FEN abolished this difference. Impulsivity was positively correlated with rCMRglu in superior and middle frontal cortex (BA 6 and 44). Hostility was positively correlated with rCMRglu in temporal cortical regions (BA 21 and 22). In conclusions, borderline pathology in the context of a Major Depressive Disorder is associated with altered activity in parietotemporal and anterior cingulate cortical regions. Controlling for the presence of BPD in future imaging studies of mood disorders may elucidate similarities and differences in regional serotonergic function in these two often comorbid disorders.

Suicide is a major public health problem with B1 million victims each year worldwide. Up to 90% of adults who commit suicide have at least one psychiatric diagnosis such as major depression, bipolar disorder (BPD), schizophrenia (SZ), substance abuse or dependence. A question that has remained unanswered is whether the biological substrates of suicide are distinct from those of the psychiatric disorders in which it occurs. The serotonin 2C receptor (5-HT 2C R) has been implicated in depression and suicide. We, therefore, compared the frequencies of its mRNA editing variants in postmortem prefrontal cortical specimens from subjects who committed suicide or who died from other causes. All suicides occurred in the context of either SZ or BPD. The non-suicide cases included subjects with either SZ or BPD as well as subjects with no psychiatric diagnosis. We identified 5-HT 2C R mRNA editing variations that were associated with suicide but not with the comorbid psychiatric diagnoses, and were not influenced by demographic characteristics (age and sex) and alcohol or drug use. These variations consisted of a significant increase in the pool of mRNA variants (ACD and ABCD) that encode one of the most prevalent and highly edited isoforms of 5-HT 2C R, that is, VSV (Val156-Ser158-Val160). Because the VSV isoform of 5-HT 2C R exhibits low functional activity, an increase in its expression frequency may significantly influence the serotonergic regulation of the brain. Thus, at least in patients with SZ or BPD, overexpression of the VSV isoform in the prefrontal cortex may represent an additional risk factor for suicidal behavior.

Reduced serotonergic activity has been associated with impulsive aggression in personality disordered