Dorsal Striatum Is Compromised by Status Epilepticus Induced in Immature Developing Animal Experimental Model of Mesial Temporal Lobe Epilepsy

Abstract

This study investigated the striatopallidal complex's involvement in status epilepticus (SE) caused by morphological neurodegenerative changes in a post-natal immature developing brain in a lithium-pilocarpine male Wistar albino rat model of mesial temporal lobe epilepsy. One hundred experimental pups were grouped by age as follows: 12, 15, 18, 21, and 25 days. SE was induced by lithium-pilocarpine. Brain sections were microscopically examined by Fluoro-Jade B fluorescence stain at intervals of 4, 12, 24, and 48 h and 1 week after SE. Each interval was composed of four induced SE pups and a control. Fluoro-Jade B positive neurons in the dorsal striatum (DS) were screened and plotted on stereotaxic rat brain maps. The DS showed consistent neuronal damage in pups aged 18, 21, and 25 days. The peak of the detected damage was observed in pups aged 18 days, and the start of the morphological sequela was observed 12 h post SE. The neuronal damage in the DS was distributed around its periphery, extending medially. The damaged neurons showed intense Fluoro-Jade B staining at the intervals of 12 and 24 h post SE. SE neuronal damage was evidenced in the post-natal developing brain selectively in the DS and was age-dependent with differing morphological sequela.

Keywords: basal ganglia; degenerative neuronal changes; dorsal striatum; epilepsy; rat brain; seizure; status epilepticus.

Figure 1

A graphical representation of the total number of experimental animals exhibiting FJB-positive neurons, comparing its incidence as follows: (A) the age of SE onset, indicating higher FJB-positive incidence at an age of 21 days; (B) after the SE time interval, indicating higher FJB-positive incidence in the survival interval of 12 h after SE. n = 100 experimental (25 control). Legend: SE—status epilepticus; D—days; h—hours.

Figure 2

Microscopic photographs showing the distribution of Fluoro-Jade B-positive neurons detected within the periphery in the dorsal striatum of the rat brain sections (magnification—20×). (A) At bregma 2.28, showing the rostral sector of the DS (age of 21 days, survival interval of 1 W). (B). At bregma 0, showing the middle sector of the DS (age of 21 days, survival interval of 24 h). (C) At bregma −2.16, showing the caudal sector of the DS (age of 21 days, survival interval of 12 h). Each figure is a construction of three visual field photos auto-aligned using CellF Software, Olympus (version 2.8). Legend: DS—dorsal striatum; GP – globus pallidus; CC—corpus callosum; EC—external capsule; IC—internal capsule.

Figure 3

Microscopic photographs showing the damaged Fluoro-Jade B-positive neurons in the dorsal striatum of the rat brain sections (magnification—40×). (A) At the age of 25 days, 12 h post SE, exhibiting intense staining of cell bodies. (B) At the age of 25 days, 1 week post SE, exhibiting some shrunken positive neurons with less stain intensity surrounded by a “dusty” background. Legend: SE—status epilepticus.

Figure 4

Schematic representation of coronal brain sections demonstrating distribution of FJD-B-positive cells in dorsal striatum of pups that experienced status epilepticus. (A) At age of 18 days, 12 h post SE. (B) At age of 18 days, 24 h post SE. (C) At age of 18 days, 48 h post SE. (D) At age of 25 days, 12 h post SE. (E) At age of 25 days, 24 h post SE. (F) At age of 25 days, 48 h post SE. Legend: SE—status epilepticus. The number in the upper left corner of each figure refers to age/survival interval. Number below each figure refers to distance from bregma [72]. Schemes were constructed using CorelDraw Software (version 11).

Figure 5

Heat map illustrating percentages of area occupied by lesion within selected intervals of rat brain’s bregma in FJB-positive neurons in 18- and 25-day-old pups at survival intervals of 12 h, 24 h, and 48 h, corresponding to destruction illustrated in Figure 4, indicating differing pattern of density by age and survival intervals based on bregma level.

Figure 6

Fluoroscopic photomicrographs showing degenerated neuron shapes detected by Fluoro-Jade B in dorsal striatum in 18-, 21-, and 25-day-old pups at survival interval of 24 h after status epilepticus. Magnification = 45×. (A) Spindle. (B) Triangular. (C) Oval.

Figure 7

Graphical presentation illustrating changes in size of FJB-positive perikarya in age groups of 18, 21, and 25 days. (A) At survival interval of 12 h after SE indicating a decrease in size by age intervals. (B) At survival interval of 24 h after SE. Legend: SE—status epilepticus indicating decrease in size between ages of 18 and 21 days.