Relationship between brain serotonin and calmodulin in young, genetically obese (ob/ob) mice.

The possible relationships between altered brain serotonin and calmodulin contents on the development of obesity were studied. Eight groups of mice separated by differences in phenotype, sex and age were used in this study. The brain contents of tryptophan, serotonin, 5-hydroxyindoleacetic acid (5-HIAA) and calmodulin were assayed. The contents of brain tryptophan showed no significant differences in any of the mice. The amount of brain serotonin in obese mice was 82% higher than that in their lean counterparts at four weeks of age, but only 11% higher at eight weeks of age. Regardless of age and sex, brain serotonin was positively correlated to the brain calmodulin in the lean mice (r = 0.559, p < 0.01), yet this was not found in obese mice. There was a strong positive correlation between serotonin and 5-HIAA in all mice (r = 0.679, p < 0.001). The elevated amount of serotonin in the brain of four-week-old obese mice is suggested to have important effects on thermoregulation in young genetically obese mice. The results also suggest that abnormal brain serotonin synthesis in obese mouse regulated by calmodulin might interact with certain factors, such as calcium ions, to complete the activation of serotonin-synthesized enzymes in the development of obesity.