Piboserod hydrochloride

The involvement of serotonin (5-HT) and/or noradrenaline in acute pruriceptive processing in the central nervous system (CNS) has been reported using antidepressants, such as milnacipran, a serotonin and noradrenaline reuptake inhibitor, and mirtazapine, a noradrenergic and specific serotonergic antidepressant; however, the roles of 5-HT receptor family in acute pruriceptive processing have not been fully elucidated in the CNS. In the present study, scratching behavior induced by chloroquine (CQ) was ameliorated by milnacipran or mirtazapine, and these effects were reversed by SB207266, a 5-HT₄ antagonist, or SB258585, a 5-HT₆ antagonist, but not by SB258585, a 5-HT₅ antagonist. Moreover, CQ-induced scratches were mitigated by intrathecal injection of 5-HT₄ agonists, such as BIMU8 and ML10302, and the 5-HT₆ agonist, WAY208466. Conversely, histamine-induced scratches were not affected by the 5-HT₄ agonists or a 5-HT₆ agonist. Similarly, the amelioration of histamine-induced scratches by these antidepressants was not reversed by the 5-HT₄, 5-HT₅, or 5-HT₆ receptor antagonist. Therefore, 5-HT is involved in the amelioration of CQ-induced scratches by milnacipran and mirtazapine, and 5-HT₄, 5-HT₅, and 5-HT₆ receptors play differential roles in acute pruriceptive processing after administration of CQ or histamine.

Previous studies have indicated that the pathogenesis of amyotrophic lateral sclerosis (ALS) is closely linked to 5-hydroxytryptamine (5-HT). To investigate this further, we administered 5-HT receptor antagonists to SOD1*G93A transgenic (ALS mouse model) and wide-type mice. This involved intraperitoneal injections of either granisetron, piboserod, or ritanserin, which inhibit the 5-HT3, 5-HT4, and 5-HT2 receptors, respectively. The transgenic mice were found to have fewer 5-HT-positive cells in the spinal cord compared with wide-type mice. We found that the administration of granisetron reduced the body weight of the transgenic mice, while piboserod and ritanserin worsened the motor functioning, as assessed using a hanging wire test. However, none of the 5-HT receptor antagonists affected the disease progression. We analyzed the distribution and/or expression of TAR DNA binding protein 43 (TDP-43) and superoxide dismutase 1 G93A (SOD1-G93A), which form abnormal aggregates in ALS. We found that the expression of these proteins increased following the administration of all three 5-HT receptor antagonists. In addition, the disease-related mislocalization of TDP-43 to the cytoplasm increased markedly for all three drugs. In certain anatomical regions, the 5-HT receptor antagonists also led to a marked increase in the number of astrocytes and microglia and a decrease in the number of neurons. These results indicate that 5-HT deficiency may play a role in the pathogenesis of amyotrophic lateral sclerosis by inducing the abnormal expression and/or distribution of TDP-43 and SOD1-G93A and by activating glial cells. 5-HT could therefore be a potential therapeutic target for amyotrophic lateral sclerosis.