Anticonvulsant effects of pentoxifylline on seizures induced by pentylenetetrazole and maximal electroshock in male mice: The role of the nitrergic pathway

Abstract

Introduction: Epilepsy remains a challenge, with one-third of patients experiencing refractory seizures despite current anti-seizure medications. The nitrergic system, which involves nitric oxide (NO) and NO synthase (NOS) enzymes, plays a complex role in seizure pathophysiology. Pentoxifylline (PTPh), an FDA-approved phosphodiesterase inhibitor, has anticonvulsant effects; however, its relationship with the pathway is unclear. This study focused at how the nitrergic system could be involved in PTPh's anticonvulsant effects.

Methods: Seizures were induced in male mice by intravenous pentylenetetrazole (PTZ) infusion (absence-like seizures), intraperitoneal PTZ injection, and maximal electroshock (generalized tonic-clonic seizures). PTPh was administered at various doses, alone or in combination with the NO precursor L-arginine, as well as non-selective (L-NAME) and selective NOS inhibitors (nNOS inhibitor 7-NI and iNOS inhibitor aminoguanidine). Seizure thresholds, latencies, incidence, and mortality were assessed. Moreover, in the next paradigm, using maximal electroshock model, we evaluate possible protective effects of PTPh against generalized tonic-clonic seizures and subsequent mortality.

Results: In the intravenous PTZ model, PTPh (≥150 mg/kg) increased the seizure threshold, potentiated by L-arginine but reduced by L-NAME and 7-nitroindazole. In the intraperitoneal PTZ model, 150 mg/kg PTPh decreased tonic seizure frequency, which was mitigated by aminoguanidine. However, PTPh failed to prolong clonic seizure latency. In the maximal electroshock test, 100 mg/kg PTPh protected against tonic seizure incidence (reduced by aminoguanidine). Although PTPh could not reduce mortality, its combination with L-NAME or 7-nitroindazole increased mortality compared with the vehicle-treated group.

Conclusion: PTPh exerted anticonvulsant effects against absence-like and generalized tonic-clonic seizures, likely through modulation of the nitrergic system involving neuronal, endothelial, and inducible NOS isoform. These findings provide novel insights into the complex interplay between NO signaling and the anticonvulsant actions of PTPh, highlighting the potential therapeutic implications of targeting the NO pathway in epilepsy management.

Keywords: Dose-response; Maximal electroshock; Nitric oxide; Pentoxifylline; Pentylenetetrazole.

Fig. 1

Experimental groups and timeline for treatment administration and behavioral tests.

Fig. 2

Effect of pentoxifylline on clonic seizure threshold. Animals received vehicle or 10, 25, 50, 100, 150, 200, and 250 mg/kg pentoxifylline, and clonic seizure thresholds were recorded as the mg/kg of pentylenetetrazole required to provoke seizure (6 mice in each group). "Data are expressed as mean ± S.E.M. *** p<0.001, ****p<0.0001 compared to vehicle. Statistical analysis was performed by one-way analysis of variance followed by the Tukey–Kramer multiple comparison post hoc test.".

Fig. 3

Impact of nitric oxide pathway mediator administration on the clonic seizure threshold. Animals received L-arginine and NOS inhibitors - Nω-Nitro-L-arginine methyl ester hydrochloride (L-NAME), 7-nitroindazole (7-NI), and aminoguanidine hydrochloride (AG), to compare alterations with the vehicle and 150 mg/kg pentoxifylline, respectively (6 mice in each group). Data are expressed as mean ± S.E.M. *** p<0.001, ****p<0.0001 compared to vehicle; ## p<0.01 compared to PTPh 150. Statistical analysis was performed by one-way ANOVA.

Fig. 4

Impact of nitric oxide pathway mediator administration on latency of clonus movements. Animals received L-arginine and NOS inhibitors - Nω-Nitro-L-arginine methyl ester hydrochloride (L-NAME), 7-nitroindazole (7-NI), and aminoguanidine hydrochloride (AG), to compare alterations with the vehicle and 150 mg/kg pentoxifylline, respectively (10 mice in each group). Data are expressed as mean ± S.E.M. ** p<0.01 compared to vehicle.

Fig. 5

Impact of nitric oxide pathway mediator administration on the frequency of tonic seizures. Animals received L-arginine and NOS inhibitors - Nω-Nitro-L-arginine methyl ester hydrochloride (L-NAME), 7-nitroindazole (7-NI), and aminoguanidine hydrochloride (AG), to compare alterations with the vehicle and 150 mg/kg pentoxifylline, respectively (10 mice in each group). Data are expressed as median with IQR. * p<0.05, ** p<0.01 compared to vehicle; # p<0.05 compared to PTPh 150. Statistical analysis was performed using the Kruskal– Walli’s test, followed by post hoc Dunn’s test.