Determination of seizure susceptibility to pentylenetetrazol

To assess seizure susceptibility, mice were injected i.p. with 60 mg/kg pentylenetetrazole (PTZ) 48 h after LPS or vehicle treatment (Sigma, St. Louis, MO, USA). Pentylenetetrazole may have multiple mechanisms of action in neurons, one of which is strongly correlated with its affinity for the picrotoxin binding site on the GABA_A receptor complex [29, 30]. Seizure activity was video recorded during an observation period of 2 h after PTZ injection. Behavioral seizures were scored every 5 min according to a previously defined scale [31, 32] as follows: stage 1 (exploring, sniffing, and grooming ceased and immobility); stage 2 (forelimb and/or tail extension, appearance of a rigid posture); stage 3 (isolated myoclonic jerks, with brief twitching movements); stage 4 (forelimb clonus and partial rearing); stage 5 (forelimb clonus, rearing, and falling); and stage 6 (generalized tonic-clonic activity with loss of postural tone, often resulting in death).