Epilepsy Research 126 (2016) 16–25 Contents lists available at www.sciencedirect.com Epilepsy Research journa l h om epa ge: www.elsevier.com/locate/epilepsyres Seizures triggered by pentylenetetrazol in marmosets made chronically epileptic with pilocarpine show greater refractoriness to treatment Josy Carolina C. Pontes a , Thiago Z. Lima b , Claudio M. Queiroz c , Simone M. Cinini a , Miriam M. Blanco a , Luiz E. Mello a,∗ a Departamento de Fisiologia, Universidade Federal de São Paulo, Rua Pedro de Toledo 669, 3 andar, São Paulo, SP 04039-032, Brazil b Hospital Israelita Albert Einstein, Avenida Albert Einstein, 627, São Paulo, SP 05652-000, Brazil c Brain Institute, Universidade Federal do Rio Grande do Norte, Avenida Nascimento de Castro, 2155, Natal, RN 59056-450, Brazil a r t i c l e i n f o Article history: Received 12 March 2016 Received in revised form 29 May 2016 Accepted 25 June 2016 Available online 27 June 2016 Keywords: Epilepsy Pharmacoresistance Pentylenetetrazole Pilocarpine Anti-epileptic drugs Animal model a b s t r a c t The efficiency of most of the new antiepileptic drugs (AEDs) on clinical trials still falls short the success reported in pre-clinical studies, possibly because the validity of the animal models is insufficient to fully represent the human pathology. To improve the translational value for testing AEDs, we propose the use of non-human primates. Here, we suggest that triggering limbic seizures with low doses of PTZ in pilocarpine-treated marmosets might provide a more effective basis for the development of AED. Mar- mosets with epileptic background were more susceptible to seizures induced by PTZ, which were at least 3 times longer and more severe (about 6 times greater frequency of generalized seizures) in comparison to naïve peers. Accordingly, PTZ-induced seizures were remarkably less attenuated by AEDs in epilep- tic than naïve marmosets. While phenobarbital (40 mg/kg) virtually abolished seizures regardless of the animal’s background, carbamazepine (120 mg/kg) and valproic acid (400 mg/kg) could not prevent PTZ- induced seizures in epileptic animals with the same efficiency as observed in naïve peers. VPA was less effective regarding the duration of individual seizures in epileptic animals, as assessed in ECoG (p = 0.05). Similarly following CBZ treatment, the behavioral manifestation of generalized seizures lasted longer in epileptic (p < 0.05), which were also more frequent than in the naïve group (p < 0.05). As expected, epilep- tic marmosets experiencing stronger seizures showed more NPY- and FosB-immunostained neurons in a number of brain areas associated with the generation and spread of limbic seizures. Our results sug- gest that PTZ induced seizures over an already existing epileptic background constitutes a reliable and controllable mean for the screening of new AEDs. © 2016 Elsevier B.V. All rights reserved. 1. Introduction Epilepsy is a common neurological disorder that affects at least 50 million people worldwide (Loscher and Schmidt, 2002). Despite recent developments of anti-epileptic drugs and innovative approaches in the epilepsy treatment (Loscher et al., 2013) 30% of patients with temporal lobe epilepsy (TLE) still are unable to have Abbreviations: AEDs, antiepileptic drugs; CBZ, carbamazepine; ECoG, electro- corticogram; LFP, local field potential; PB, phenobarbital; PFA, paraformaldehyde; PSD, power spectrum density; PTZ, pentylenetetrazole; SE, status epilepticus; SNr, substantia nigra pars reticulate; SRF, serum response factor; SRSs, spontaneous recurrent seizures; TLE, temporal lobe epilepsy; VPA, valproic acid. ∗ Corresponding author. E-mail address: lemello@unifesp.br (L.E. Mello). their seizures controlled as a consequence of pharmacoresistance (McKeown and McNamara, 2001) and also do not meet the criteria for surgical intervention (Centeno et al., 2006). In the more recent years, as a first choice approach for seizure control, pharmacology has not brought into clinical practice the same successes reported in pre-clinical trials (Loscher and Schmidt, 2002). One possible reason for such failure relies on the fact that most AEDs are tested in ani- mal models that not completely mimic human TLE and are mostly based in acute, chemically- or electrically-evoked seizures (Bialer and White 2010; Loscher and Schmidt, 2011; White and Loscher, 2014). In contrast, one of the key hallmarks of epilepsy, including TLE, is the occurrence of unpredicted, spontaneous (not evoked) and recurrent seizures (SRSs). In animal models of TLE, sponta- neous seizures are often observed in the chronic phase that ensues http://dx.doi.org/10.1016/j.eplepsyres.2016.06.012 0920-1211/© 2016 Elsevier B.V. All rights reserved.