Serotonin Uptake In Blood Platelets Research Articles

P.2.b.025 Serotonin uptake in blood platelets is related to cingulate cortex activation

P.2.b.025 Serotonin uptake in blood platelets is related to cingulate cortex activation

Effect of flunarizine and calcium on serotonin uptake in human and rat blood platelets and rat synaptosomes

Calcium and the calcium overload blocker flunarizine exert profound effects on mood. We therefore studied the effect of calcium and flunarizine on serotonin uptake in human and rat blood platelets and in rat synaptosomes. Calcium (1.3 mmol/L) had a weak inhibiting effect on serotonin uptake in blood platelets, whereas no effect was observed in synaptosomes. Flunarizine inhibited serotonin uptake in a concentration dependent manner with an IC 50 value of 1 μmol/L in blood platelets and 5 μmol/L in synaptosomes. The inhibition did not depend on the presence of extracellular calcium indicating that the effect is not coupled to a blockade of cellular calcium influx. In human blood platelets, the inhibition was of the noncompetitive type. These results indicate that flunarizine interacts directly with the 5-HT uptake site. The relatively high concentration of flunarizine required to inhibit 5-HT uptake may question the clinical importance of this effect.

Flunarizine inhibits serotonin uptake in blood platelets with and without calcium.

Flunarizine inhibits serotonin uptake in blood platelets with and without calcium.

Genetic control of serotonin uptake in blood platelets: A twin study

Platelet serotonin (5HT) uptake was studied in 13 pairs of monozygotic (MZ) twins, 13 pairs of dizygotic (DZ) twins, and 14 pairs of unrelated normal volunteers. Significant intraclass correlations (ICC) in the affinity ( K m) of 5HT uptake in the blood platelets of MZ and DZ twins and unrelated pairs were found. However, the ICC for maximum velocity ( V max) was significant only in MZ and DZ twins. The ICC of the V max of 5HT uptake of MZ twins was significantly greater than that of DZ twins and unrelated pairs. This suggests that the V max of 5HT uptake in blood platelets is , in part, heritable. Thus, low platelet 5HT uptake ( V max) in major depression and other disorders may be genetically determined.

Effect of lithium carbonate on serotonin uptake in blood platelets of patients with affective disorders

Lithium carbonate treatment for 2–3 weeks produced a significant decrease in the maximum velocity (V max) of serotonin (5-HT) uptake, a measure of the number of 5-HT uptake sites in blood platelets from bipolar patients. The decrease was more pronounced in bipolar manic patients than bipolar depressed patients. There was no significant affect on the affinity for 5-HT (K m) of the uptake sites in the platelets of manic or depressed bipolar patients although K m did decrease (indicating increased affinity) in the majority of subjects from both groups of patients. However, lithium treatment of at least 1 year duration was associated with significant increases in V max without affecting K m. Lithium in vitro, at concentrations up to 1 mM, had no effect on the K m or V max of 5-HT uptake in blood platelets of normal controls. The possible mechanisms of the inhibitory and stimulatory effect of lithium carbonate treatment on platelet 5-HT uptake are discussed.

Serotonin Uptake in Blood Platelets of Acute Schizophrenics-Reply

<h3>In Reply.—</h3> Modai et al are correct in pointing out that their method permits the assessment of active uptake of serotonin. We apologize for our misunderstanding of their means of estimating passive diffusion. However, the use of only a single tube to assess passive diffusion and of duplicate tubes to assess total uptake is questionable, because the data on passive diffusion contribute as much to the measurement of active uptake as do those on total uptake. The important issue of whether schizophrenic patients suffering acute exacerbation have decreased active uptake of serotonin in their platelets requires further study, because we cannot confirm the report by Modai et al of low uptake in schizophrenics. S. Stahl, MD, PhD, and P. Berger, MD, of Stanford (Calif) University also have not found decreased uptake of serotonin in the platelets of schizophrenics not receiving medication (oral communication, Nov 15, 1981). There could be some differences between

Serotonin uptake in blood platelets of psychiatric patients

• Platelet serotonin (5-HT) uptake was determined in 72 newly admitted, unmedicated psychiatric patients. Decreased maximum velocity (V max ) of 5-HT uptake was present in unipolar and bipolar depressed patients as well as schizoaffective depressed patients. The apparent Michaelis constant (k m ) of 5-HT uptake was normal in these groups, as was V max and K m in manicdepressive and chronic schizophrenic patients. Treatment of depressed patients with notriptyline hydrochloride or imipramine hydrochloride increased K m significantly. There was a trend for the increase in K m in the nortriptyline-treated patients to correlate with clinical improvement. Decreased 5-HT uptake in platelets provides additional evidence for the role of 5-HT in the pathophysiologic process of some forms of depression.