Abstract:

Objective: "Genetic Absence Epilepsy Rats from Strasbourg" (GAERS), an inbred Wistar strain, serve as an experimental venue. These rats generate spontaneous spike-and-wave discharges (SWD) and have increased yaminobutyric acid (GABA) levels in the ventrolateral thalamus (VLT). Recently, substantia nigra pars reticulata (SNpr) was reported to act as an endogeneous inhibitory mechanism in the generation, onset and maintenance of various types of seizures. The presence of tonic control exerted by SNpr in absence seizures should also be tested in GAERS. Methods: In this current study, GABA and Lglutamic acid release in VLT of GAERS with partial bilateral electrolytic lesions of SNpr was evaluated by using microdialysis technique with fluorescent detection. Results: GABA levels in VLT were 0.12±0.04 pM and 0.24±0.08 pM in sham-lesioned and SNprlesioned GAERS, respectively. L-glutamic acid level was found to be 0.415±0.150 pM in shamlesioned group and 0.324±0.094 pM in SNprlesioned GAERS. Statistical analysis revealed no significant difference between sham-lesioned and SNpr-lesioned rats. The number and the duration of SWD were also similar in two groups. Conclusion: These findings show that SNpr does not exert a tonic control in GAERS and we assume that intact SNpr acts as a site that may exert an inhibition on target structures when activated in GAERS. Key Words: GAERS (Genetic Absence Epilepsy Rats from Strasbourg), GABA (yaminobutyric acid), Substantia nigra, Ventrolateral thalamus, Absence epilepsy, Microdialysis, Nigral control of epilepsy.

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