Figure 1.
Susceptibility of Brd2 heterozygous KO mice (+/-) and control littermates (+/+) to flurothyl-induced seizures.
Seizure threshold is depicted in µl of flurothyl necessary to induce specific seizure type (Mean±S.E.M.). (A) In females, tonic-clonic seizures in Brd2+/- mice had significantly lower threshold than in Brd2+/+ littermate controls. (B) In males, clonic seizures in Brd2+/− mice had significantly lower threshold than in Brd2+/+ littermate controls.
Figure 2.
Combined EEG/videorecordings of spontaneous seizures in Brd2+/− mice.
(A) Scheme of head mounted electrodes with one reference (REF) in the nasal bone, one common ground in the occipital area, and active electrodes in the left and right frontal area (LF, RF, respectively) and in both occipital areas (BiO). (B) EEG recordings of interictal discharges (one indicated by an arrow) in a Brd2+/− mouse associated with myoclonic jerks (twitches of body musculature). (C) EEG recordings from the same mouse showing a long EEG seizure consisting of spike-and-wave pattern. Onset of seizure is marked by an arrowhead. (D) EEG recordings of spindle-shaped sharp wave episodes associated with behavioral freezing in another Brd2+/− mouse. Onset of two spindles (about 3 s and 1 s long) is marked by arrowheads. (E) Frozen video frames (under infrared lighting) showing onset of a violent clonic seizure (E1) in a Brd2+/− mouse and the end of status epilepticus (after more than an hour of clonic seizures) in the same mouse (E2).
Figure 3.
Expression of GABAergic markers in the Brd2+/− mice and Brd2+/+ littermate controls.
(A) Simplified scheme of a direct basal ganglia pathway, which includes primary motor cortex, caudate-putamen (CPu) and globus pallidus (GP), substantia nigra reticulata (SNR), and its outputs the superior colicullus (SC) and ventral medial thalamic nucleus (VM). Dark arrows indicate glutamatergic outputs, while grey arrows mark GABAergic projections [39]. (B) Number of PVA-immunopositive neurons and density of GAD67 staining per neurons in the SNR of Brd2+/− mice (+/−) versus Brd2+/+ littermate controls (+/+; expressed in % of control values; mean ±S.E.M.). While the number of PVA-positive neurons significantly decreased, the GAD67 content within neurons slightly increased in the SNR of Brd2+/− mice. (C) GAD67 content in the fibers of the intermediate gray matter layer (inter) of the SC was decreased in Brd2+/− mice vs. Brd2+/+ controls. However, the GAD67 content in the deep gray matter layer of the SC (deep) was not different between Brd2+/− mice and. Brd2+/+ controls. This finding is consistent with presence of GABAergic terminals originating from the SNR in the intermediate, but not deep, gray matter layer of the SC. (D) Number of GAD67-immunopositive neurons in the CPu and GP was profoundly decreased in both parts of the striatum in Brd2+/− mice compared to Brd2+/+ littermates illustrated further in microphotographs of upper outer quadrant of CPu in a Brd2+/+ (E) and Brd2+/− mouse (F). (G) Sex-specific difference in the relative number of PVA-positive neurons in the CPu. Males irrespective of genotype had about 30% fewer PVA neurons than females. There was no significant effect of genotype. (H) There was a significant decrease in number of GAD67-, but not PVA-immunopositive neurons in the primary motor cortex in Brd2+/− mice versus Brd2+/+ controls. (I) GAD67 content in the fibers of the ventral medial thalamic nucleus (VM) in the Brd2+/− mice was significantly decreased compared to Brd2+/+ controls. (J) Number of PVA-immunopositive neurons in the hilar area of the dentate gyrus in both dorsal and ventral hippocampi was unchanged as in Brd2+/− mice compared to Brd2+/+ littermates.