Introduction: Bipolar Disorder (BD) has been increasingly associated with abnormalities in neuroplasticity, and previous studies demonstrated that neurotrophin-3 (NT-3) plays a role in the pathophysiology of mood disorders. The influence of medication in these studies has been considered a limitation. Thus, studies with drug-free vs. medicated patients are necessary to evaluate the role of medication in serum NT-3 levels.
Methods: Twenty manic and depressive drug-free and 20 medicated patients with BD type I were matched with 20 controls for sex and age. Patients were assessed using SCID-I, YMRS and HDRS. The drug-free patients did not receive psychotropic medication for at least two weeks before entering the study. Serum NT-3 levels were assessed using sandwich-ELISA.
Results: Serum NT-3 levels in drug-free and medicated patients is increased when compared with controls (2.51 ± 0.59, 2.56 ± 0.44 and 1.97 ± 0.33, respectively, p < 0.001 for drug-free/medicated vs. control). Serum NT-3 levels do not differ between medicated and drug-free patients. When analyzing the patients according to mood states, serum NT-3 levels are increased in both manic and depressive episodes, as compared with controls (2.47 ± 0.43, 2.60 ± 0.59 and 1.97 ± 0.33, respectively, p < 0.001 for manic/depressive patients vs. controls).
Conclusions: Results suggest that increased serum NT-3 levels in BD are more likely to be associated with the pathophysiology of manic and depressive symptoms rather than solely a result of medication use.