, 2011). In Sprague–Dawley rats, PTZ at 50 mg/kg (IP) induced seizure and overt convulsions (DeBoer & Friedrichs, 2009). Similar to our results, the PTZ threshold for clonic convulsions with IV infusion in Sprague–Dawley rats was 59 (3) mg/kg (Mirski, Rossell, McPherson, & Traystman,

1994). In contrast, the convulsion threshold dose in adult (8 weeks) Wistar–Unilever was reported to be much lower at 21.3 ± 2.6 mg/kg (Himmel, 2008) suggesting differences between rat strains. The murine PTZ threshold model is usually associated with higher doses to induce clonic (70 mg/kg) and tonic (130 mg/kg) convulsions (CD-1 mice; Mandhane, Aavula, & Rajamannar, 2007). Cynomolgus monkeys are used as a large animal species as they lack the genetic predisposition Selisistat to seizure aforementioned but also present genetic polymorphism closer to the human population (Higasino et al., 2009 and Watanabe et al., 2007). Cynomolgus monkeys may be useful to identify seizure potential of some pharmaceutical candidates when rats failed to identify seizure activity (Markgraf, DeBoer, & Cirino, 2010) making the non-human primate a valuable model in some circumstances. In comparison to the non-human primate, whose prefrontal cortex layers are well-defined (Fuster, 2008) the cytoarchitechture of the dog prefrontal cortex appears more primitive, partly due to the vague separation between the prefrontal

and motor cortexes (Kosmal, Stepniewska, & Markow, Imatinib in vitro 1983). The growth of the prefrontal cortex and granularization of layer IV (internal granular layer) are characteristic in non-human primates as well as in humans (Fuster, 2008). While few double bouquet cells are present in carnivores compared to primates (10 vs hundreds in a ~ 25 mm histological section), these cells, which are y-aminobutyric acid (GABA) containing interneurons, are completely absent in rodents (Yáñez et al., 2005). In addition, there are a greater number of GABAergic neurons in the non-human primate and human in comparison

to the rat (Yáñez et al., 2005). Finally, as in the human neocortex, Metalloexopeptidase there are hundreds of inhibitory networks established from each double bouquet cell in the non-human primate (Yáñez et al., 2005). When further considering species selection, the argument that the most sensitive species should be preferred in safety assessments may be rejected when seizures are noted in Beagle dogs on the basis of the poor translational potential of this species and the risk of discontinuing development of a drug candidate that would otherwise be shown as safe at doses that are clinically effective in humans. It remains that situations where humans are more sensitive than the Beagle dog to drug-induced seizure were reported (unpublished personal communications) and selection of the test species should be done carefully and in conjunction with regulators, when possible.