Background: Serotonergic (5-HT) dysfunction has been hypothesized in mania; however platelet studies on the 5-HT uptake rate and the 5-HT transporter have revealed inconsistent results. To the best of our knowledge no studies have been conducted on the 5-HT2 receptor status in mania.
Methods: We determined density (Bmax) and dissociation constant (Kd) of 5-HT2 receptors in the platelets of 29 normal control and 29 manic subjects using 125I-ketanserin as the binding radioligand. The manic patients were assessed for the same after 14 days of treatment with lithium (n = 14) and after return to premorbid levels of functioning (n = 5).
Results: There were no significant differences in the Bmax (3.51 +/- 3.04 vs. 3.14 +/- 3.44 fmol/mg protein, p = ms) values between normal control and manic subjects. In comparison to the baseline values Bmax at day 14 (3.49 +/- 3.68 vs. 2.18 +/- 1.90 fmol/mg protein, p = ns) and following recovery (1.17 +/- 0.85 vs. 1.29 +/- 1.13 fmol/mg protein, p = ns) did not show any significant difference.
Conclusions: Our findings preliminarily suggest that the platelet 5-HT2 receptor is neither a state marker nor a trait marker in mania; however studies on the 5-HT2 receptor using positron-emission tomography ligands will help in conclusively ruling out the involvement of this receptor in mania.