†These authors contributed equally.
Rats were divided into six groups: sham/control, Dl-3-n-butylphthalide, P1 (low phenytoin, 100 mg/kg), P2 (high phenytoin, 200 mg/kg), NP1 (Dl-3-n-butylphthalide 80 mg/kg, phenytoin 100 mg/kg), NP2 (Dl-3-n-butylphthalide 80 mg/kg, phenytoin 200 mg/kg). Hematoxylin/eosin and Nissl staining showed that, compared to the sham/control group, the Dl-3-n-butylphthalide group had no obvious hippocampal and cerebellar neuron loss, but there was a significant neuron loss in the P1 and P2 groups (P < 0.05), which was more obvious in the P2 group (P < 0.05). The positive expression of Bax and Bcl-2 proteins in hippocampal and cerebellar neurons was not significantly different between sham and Dl-3-n-butylphthalide groups; however, compared to sham, Bax expression was significantly increased and Bcl-2 was significantly decreased in the hippocampal and cerebellar neurons of rats in both P1 and P2 groups (P < 0.05), being more obvious in the P2 group (P < 0.05). Furthermore, the administration of Dl-3-n-butylphthalide attenuated the deleterious effects of phenytoin (P < 0.05). Our results indicate that phenytoin causes apoptosis of hippocampal and cerebellar neurons in rats in a dose-dependent manner, with the effect of a higher dose being more obvious, whereas, Dl-3-n-butylphthalide inhibits the phenytoin-induced apoptosis of neurons and has a neuroprotective role.