An animal model of generalized nonconvulsive status epilepticus: immediate characteristics and long-term effects

Absence seizures are traditionally believed to have no significant long-term neurological consequences, but few basic scientific studies have examined the effects of absence seizures on neuronal function, especially regarding absence status epilepticus. We developed a model of generalized nonconvulsive status epilepticus (GNCSE) in rats to study behavioral, functional, and histological effects of GNCSE. Using repetitive timed injections of low-dose pentylenetetrazol (PTZ), a state of prolonged behavioral arrest and immobility associated with frequent generalized spike-wave discharges on EEG could be induced for hours, consistent with GNCSE. GNCSE occurred reproducibly in adult rats, but surprisingly not in juvenile rats or adult mice. There was no evidence of pathological damage following GNCSE using Fluoro-Jade B and Cresyl Violet histological methods. Although a transient, subtle deficit in place learning occurred in PTZ-treated rats, there were no long-term behavioral effects of GNCSE on spatial learning or sensorimotor function. However, 1 week after a single episode of GNCSE, there was an increase in absence seizures in response to a repeat dose of PTZ compared to controls. These results indicate that an animal model of GNCSE can be generated and that even in the absence of overt neuronal damage, GNCSE may produce functional changes in neurons that alter electrical excitability of neural circuits.