Differential Contribution of 5-HT, 5-HT, and 5-HT Receptors to Acute Pruriceptive Processing Induced by Chloroquine and Histamine in Mice.

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-HT antagonist, or SB258585, a 5-HT antagonist, but not by SB258585, a 5-HT antagonist. Moreover, CQ-induced scratches were mitigated by intrathecal injection of 5-HT agonists, such as BIMU8 and ML10302, and the 5-HT agonist, WAY208466. Conversely, histamine-induced scratches were not affected by the 5-HT agonists or a 5-HT agonist. Similarly, the amelioration of histamine-induced scratches by these antidepressants was not reversed by the 5-HT, 5-HT, or 5-HT receptor antagonist. Therefore, 5-HT is involved in the amelioration of CQ-induced scratches by milnacipran and mirtazapine, and 5-HT, 5-HT, and 5-HT receptors play differential roles in acute pruriceptive processing after administration of CQ or histamine.