Bipolar Research Today is a free monthly online journal that collates and summarizes the latest research about Bipolar, including details on bipolar disorder, symptoms, treatment, depression, medication.

5HTTLPR polymorphism and enlargement of the pulvinar: unlocking the backdoor to the limbic system.

Young KA, Holcomb LA, Bonkale WL, Hicks PB, Yazdani U, German DC

Neuropsychiatry Research Program, Central Texas Veterans Health Care System, Temple, Texas 76504, USA. kayoung@medicine.tamhsc.edu

BACKGROUND: The 5HTTLPR genetic variant of the serotonin transporter (SERT), which consists of a long (SERT-l) and short (SERT-s) allele, has emerged as a major factor influencing emotional behavior and brain anatomy. The pulvinar nucleus of the thalamus projects to important limbic nuclei including the amygdala and cingulate cortex, is involved in the processing of stimuli with emotional content, and contains an abundance of SERT. METHODS: Stereological methods were used to measure pulvinar neuron number in postmortem tissue from major depressive disorder (n = 11), bipolar disorder (n = 11), schizophrenia (n = 12), and control (n = 15) specimens from the Stanley Foundation Neuropathology Consortium. The effect of SERT genotype on pulvinar volume and neuron number was investigated by using analysis of covariance. RESULTS: Analysis of covariance with diagnosis, SERT genotype, age, hemisphere, postmortem interval, and time-in-formalin covariates identified a 20% increase in pulvinar neuron number and volume in SERT-ss subjects. CONCLUSIONS: The elevated number of pulvinar neurons in subjects with a SERT-ss genotype may serve to enhance subcortical input of emotionally relevant stimuli to the limbic system, providing a mechanism for the 5HTTLPR genetic variant to affect predisposition to conditions such as major depression.

Published 6 March 2007 in Biol Psychiatry, 61(6): 813-8.
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