HRH3 and Cognitive impairment: However, the preclinical use of numerous non-imidazole-based H3R antagonists, e.g., ABT-239 and A-431404, ameliorated ketamine- and/or MK-801-induced cognitive impairments in experimental rats, demonstrating enhanced results when compared with reference antipsychotics like risperidone or olanzapine (Brown et al., 2013; Figure 2, Table 4).