Cypermethrin Exacerbates Pentylenetetrazole-induced GABAergic Interneuron Loss and Neuroinflammation in the Rat Amygdala: Neuroprotection by Valproate and Vitamin E Co-therapy

The comorbidity of epilepsy with exposure to cypermethrin may exacerbate neuropathology and compromise treatment outcomes. This study investigated the synergistic neurotoxic effects of pentylenetetrazole and cypermethrin on the amygdala and evaluated the neuroprotective potential of valproic acid (VPA) and vitamin E (Vit E). In the first phase, male Wistar rats were divided into four groups (n=9): control (corn oil), cypermethrin (4.4 mg/kg, oral), pentylenetetrazole (35 mg/kg, i.p.), and cypermethrin + pentylenetetrazole. In the second phase, four groups (n=9) received cypermethrin + pentylenetetrazole and were co-treated with VPA (100 mg/kg), Vit E (100 mg/kg), or VPA+Vit E. Amygdala tissues were analyzed for cyclooxygenase-2 (COX-2) levels, neuronal morphology (H&E), GABAergic interneuron density (parvalbumin, PV), microglial activation (Iba-1), and astrogliosis (GFAP) using immunohistochemistry and biochemical assays. Combined cypermethrin + pentylenetetrazole exposure increased brain COX-2 levels and significantly reduced the density of PV+ GABAergic interneurons and healthy neurons (H&E) in the amygdala, accompanied by a trend towards increased gliosis (GFAP, Iba-1). In the intervention phase, VPA treatment alone significantly reduced body weight. While Vit E alone modestly reduced COX-2, the combination of VPA and Vit E most effectively restored PV+ and H&E-stained cell counts and attenuated GFAP expression, suggesting enhanced neuroprotection and reduced astrogliosis. The VPA+Vit E combination also mitigated the body weight loss associated with VPA monotherapy. Cypermethrin exposure exacerbates pentylenetetrazole-induced GABAergic interneuron loss, microgliosis, and astroglyosis in the amygdala. Combined antiepileptic drug and antioxidant supplement therapy offers superior neuroprotection compared to monotherapy by ameliorating neuroinflammation, restoring inhibitory neuronal populations, and suppressing gliosis.

Key Words: Epilepsy, neuroinflammation, amygdala, valproic acid, Vitamin E