HTR3A and diabetes mellitus: Moreover increased food intake and weight gain observed under clozapine treatment can be reversed by D1, D2, 5-HT1b, 5-HT2c, and 5-HT3 agonists, arguing that dopaminergic and serotoninergic receptors are involved in antipsychotic-induced weight gain, insulin resistance, and diabetes (Kaur and Kulkarni, 2002).