ORIGINAL ARTICLE Combined sub-threshold dosages of phenobarbital and low-frequency stimulation effectively reduce seizures in amygdala-kindled rats Azam Asgari • Saeed Semnanian • Nafiseh Atapour • Amir Shojaei • Homeira Moradi • Javad Mirnajafi-Zadeh Received: 12 January 2014 / Accepted: 15 February 2014 Ó Springer-Verlag Italia 2014 Abstract Low-frequency stimulation (LFS) is a potential therapy utilized in patients who do not achieve satisfactory control of seizures with pharmacological treatments. Here, we investigated the interaction between anticonvulsant effects of LFS and phenobarbital (a commonly used med- icine) on amygdala-kindled seizures in rats. Animals were kindled by electrical stimulation of basolateral amygdala in a rapid manner (12 stimulations/day). Fully kindled ani- mals randomly received one of the three treatment choices: phenobarbital (1, 2, 3, 4 and 8 mg/kg; i.p.; 30 min before kindling stimulation), LFS (one or 4 packages contained 100 or 200 monophasic square wave pulses, 0.1-ms pulse duration at 1 Hz, immediately before kindling stimulation) or a combination of both (phenobarbital at 3 mg/kg and LFS). Phenobarbital alone at the doses of 1, 2 and 3 mg/kg had no significant effect on the main seizure parameters. LFS application always produced anticonvulsant effects unless applied with the pattern of one package of 100 pulses, which is considered as non-effective. All the sei- zure parameters were significantly reduced when pheno- barbital (3 mg/kg) was administered prior to the application of the non-effective pattern of LFS. Phenobarbital (3 mg/kg) also increased the anticonvulsant actions of the effective LFS pattern. Our results provide an evidence of a positive cumulative anticonvulsant effect of LFS and phenobarbital, suggesting a potential combination therapy at sub-threshold dosages of phenobarbital and LFS to achieve a satisfactory clinical effect. Keywords Epilepsy Á Kindling Á Low-frequency stimulation Á Phenobarbital Á Seizure Á Animal model Introduction Temporal lobe epilepsy is one of the most common type of epilepsies in which different areas of the limbic system including amygdala and hippocampus are involved. Anti- convulsant medication is yet the most common method for treating patients with epilepsy, effective in controlling the seizures in up to 70 % of patients. However, the rest continue to suffer from seizures, illness and risk of mor- tality [1]. The GABAergic system is the primary or the secondary target of many of the available anticonvulsants drugs. These drugs potentiate GABA A receptor action directly through interaction with the receptor or indirectly by increasing GABA release [2]. Phenobarbital and other barbiturates exert their antiepileptic effects by facilitating GABA-mediated inhibition via allosteric interaction with the neuronal postsynaptic GABA A receptors [3]. The number of patients with epilepsy, particularly of temporal lobe origin, who are pharmacoresistant (specially to phe- nobarbital) is remarkably large and treatment-resistant epilepsy is one of the most common problems in neurology [4]. On the other hand, surgical resection as another pos- sible treatment for some epileptic patients is associated A. Asgari Á S. Semnanian Á A. Shojaei Á H. Moradi Á J. Mirnajafi-Zadeh (&) Department of Physiology, Faculty of Medical Sciences, Tarbiat Modares University, PO Box 14115-331, Tehran, Iran e-mail: mirnajaf@modares.ac.ir N. Atapour Neuroscience Research Center, Kerman University of Medical Sciences, Kerman, Iran N. Atapour Department of Medicine (Royal Melbourne Hospital), Melbourne Brain Centre, University of Melbourne, Parkville, VIC, Australia 123 Neurol Sci DOI 10.1007/s10072-014-1693-9