Abstracts

Rationale: Absence epilepsy is a type of genetic epilepsy characterized by non-convulsive seizures, beginning in childhood or adolescence. It is a disease characterized by generalized seizures that occur at the end of a latent period called postpartum epileptogenesis. The mechanism of action of the basal ganglia in the development of the epileptogenesis has not been clarified yet.

In the present study, 30-day-old genetic absence epilepsy rats from Strasbourg (GAERS) before the onset of absence seizures were used. A comparison between neuronal counting and densitometric measurement was carried out following a chemical lesion in the nigro-striatal dopaminergic pathway.

Methods: A chemical lesion in the nigro-striatal dopaminergic pathway was carried out by injecting 6-Hydroxydopamine (6-OHDA) into the medial forebrain bundle (AP:-1.4, ML:1.6, V:7.1) of 30-day-old GAERS rats using stereotaxic surgery (n=5). The chemical lesion was confirmed by behavioral apomorphine induced evaluation and then the brains were removed following trans cardiac perfusion with 10% neutral buffered formalin under deep anesthesia. Thereafter, 40 µm coronal sections were immunohistochemically stained by tyrosine hydroxylase. Dopaminergic immunoreactivity in the SNpc region was evaluated in two different ways by counting of the stained neurons and densitometric measurements of the neurons. Brain sections were photographed with a microscope (Olympus DP72 microscope Tokyo, Japan) and dopaminergic neurons were evaluated in two different ways by counting the stained neurons and measure densitometric measurements of the neurons (Image J software, USA). In order to compare the densitometric measurement and the neuronal counting, 6-OHDA lesioned animals were compared with the naive animals. The measurements of neuronal counting were performed as follows: (counting of 6-OHDA/counting of naive)X100. The measurements of densitometry were performed: (densitometry of 6-OHDA/ densitometry of naive)X100. Data were expressed as mean±standard error of mean. Differences between groups were analyzed by Student’s t test using GraphPad Prism.

Results: There is a statistically significant difference between densitometric measurement and neuron counting (****p < 0,0001). Dopaminergic degeneration was demonstrated in both densitometric measurement and neuronal counting (densitometry: 76.6±5.43; counting: 24.43±4.91).