Short-term use of antiepileptic drugs is neurotoxic to the immature brain

Abstract

Previous studies have shown that the long-term use of antiepileptic drugs can cause nervous system damage. However, short-term antiepileptic drug treatment is frequently given to infants, especially neonates, to control seizure. Whether the short-term use of antiepileptic drugs is neurotoxic remains unclear. In the present study, immature rats, 3-21 days of age, were intraperitoneally injected with phenobarbital and/or topiramate for 3 consecutive days. Hematoxylin-eosin and immunohistochemical staining revealed that phenobarbital and topiramate, individually or in combination, were cytotoxic to hippocampal CA1 neurons and inhibited the expression of GluR1 and NR2B, excitatory glutamate receptor subunits. Furthermore, the combination of the two drugs caused greater damage than either drug alone. The results demonstrate that the short-term use of antiepileptic drugs damages neurons in the immature brain and that the combined use of antiepileptic drugs exacerbates damage. Our findings suggest that clinicians should consider the potential neurotoxic risk associated with the combined use of antiepileptic drugs in the treatment of seizure.

Keywords: NSFC grant; antiepileptic drugs; glutamate receptor; hippocampus; immature brain; nerve regeneration; neural regeneration; seizure; synaptic plasticity.

Figure 1

Effects of phenobarbital (PB) and topiramate (TPM) on the morphology of neurons in the hippocampal CA1 region in immature rats (hematoxylin-eosin staining, × 100). In the control group, hippocampal neurons were distributed in a regular and uniform manner. In the PB, TPM and TPM + PB groups, hippocampal neurons were irregularly arranged. Arrows indicate hippocampal neurons. PD3, 7, 14, 21: Postnatal days 3, 7, 14, 21 (indicating when the rat was injected with drug).

Figure 2

Effects of phenobarbital (PB) and topiramate (TPM) on AMPA receptor GluR1 immunoreactivity in the hippocampal CA1 region in immature rats. (A) GluR1 immunoreactivity in the hippocampal CA1 region in immature rats (immunohistochemical staining, × 400). The brown color represents receptors on the cell membrane (arrows). (B) Quantification of GluR1-immunoreactive cells. All data are expressed as the mean ± SD. *P < 0.05, vs. control group; #P < 0.05, vs. PB group; †P < 0.05, vs. TPM group; §P < 0.05, vs. PD3; ‡P < 0.05, vs. PD7; ΔP < 0.05, vs. PD14 (two-way ganalysis of variance and Tukey's post hoc test). PD3, 7, 14, 21: Postnatal days 3, 7, 14, 21 (indicating when the rat was injected with drug); AMPA: α-amino-3-hydroxy-5-methyl-4-isoxazole-propionic acid.

Figure 3

Effects of phenobarbital (PB) and topiramate (TPM) on NMDA receptor NR2B immunoreactivity in the hippocampal CA1 region in immature rats. (A) NR2B immunoreactivity in the hippocampal CA1 region in immature rats (immunohistochemical staining, × 400). The brown color represents receptors on the cell membrane (arrows). (B) Quantification of NR2B-immunoreactive cells. All data are expressed as the mean ± SD. *P < 0.05, vs. control group; #P < 0.05, vs. PB group; †P < 0.05, vs. TPM group; §P < 0.05, vs. PD3; ‡P < 0.05, vs. PD7; ΔP < 0.05, vs. PD14 (two-way analysis of variance and Tukey's post hoc test). PD3, 7, 14, 21: Postnatal days 3, 7, 14, 21 (indicating when the rat was injected with drug); NMDA: N-methyl-D-aspartate.