Dopamine Transporter Genotype Influences the Attention Deficit in Korean Boys with ADHD

Attention appears to be inheritable, stable and influenced by genetic factors. The use of the Continuous Performance Test (CPT), as an endophenotypic measure, is valuable for genetic studies because it may show increased sensitivity to specific dimensions in attention deficit hyperactivity disorder. However, few studies have been designed to examine the influence of the genotype on attention level measured by CPT in ADHD patients. This study examinee the difference between 10/10 and 10/* genotype in the attention deficits measured by the CPT in ADHD patients. Forty-four unrelated ADHD patients were recruited from the psychiatric outpatients' clinic at Kangbuk Samsung Hospital. Two child psychiatrists made the diagnoses of ADHD using the DSM-IV diagnostic criteria. The genomic DNA was extracted from the blood, and analyzed to determine the genotype. A 40-base pair variable number of tandem repeats (VNTR) polymorphism in the 3' untranslated region was amplified. The attention deficits were measured by the test of variables of attention (T.O.V.A.). Between the 10/10 genotype and 10/* genotype, standard scores of the T.O.V.A were compared using a Mann-Whiney test. A comparison with the 10/10 genotype and 10/* genotype showed that those patients with the 10/10 genotype made less omission errors in the first quarter of the test (p < 0.05, by Mann-Whiney test). No significant differences were observed in the errors of commission, response time, variability. This study found that the 10/10 genotype made less omission errors on the T.O.V.A. This suggests that the dopamine transporter genotype influences the attention deficits measured by T.O.V.A.

Effects of Fluoxetine on Membrane Potential and Ionic Currents in RINm5F Insulinoma Cells / 대한정신약물학회지

OBJECTIVE: The purpose of this study was to investigate the effects of fluoxetine (Prozac) on membrane potential and ionic currents in RINm5F insulinoma cells. METHODS: Membrane potential and ionic currents in RINm5F cell were recorded by using whole-cell and perforated-patch clamp techniques. RESULTS: Under current clamp conditions, diazoxide (200 microM), an activator of K ATP channels, induced a hyperpolarization of the resting membrane potential (-16.1+/-1.4 mV, n=), which was accompanied by a abolition of action potential firing. This diazoxide-induced hyperpolarization was blocked by glibenclamide (10 microM). Fluoxetine produced significant depolarization of membrane potential (15.9+/-3.1 mV, n=) and blocked diazoxide-induced hyperpolarization. Diazoxide activated inward currents in the presence of high external K + (90 mM) at a holding potential of -60 mV. Fluoxetine suppressed diazoxide-activated currents in a concentration-dependent (IC 50 =.84 microM) manner. However, the inhibitory action of fluoxetine was not specific to K ATP currents because it also inhibited both voltage-activated K + and Ca 2+ currents in a concentration-dependent manner. K ATP currents were more sensitive to fluoxetine block than both voltage-activated K + and Ca 2+ currents. CONCLUSION: Our results indicate that fluoxetine increased excitability of RINm5F cells mainly by the preferential block of K ATP currents. Fluoxetine-induced depolarization may influence insulin secretion in insulinoma cells.