Reorganization of Parvalbumin Immunopositive Perisomatic Innervation of Principal
Cells in Focal Cortical Dysplasia Type IIB in Human Epileptic Patients
National Brain Research Program(2017-1.2.1-NKP-2017-00002)
Focal cortical dysplasia (FCD) is one of the most common causes of drug-resistant
epilepsy. As several studies have revealed, the abnormal functioning of the perisomatic
inhibitory system may play a role in the onset of seizures. Therefore, we wanted to
investigate whether changes of perisomatic inhibitory inputs are present in FCD. Thus,
the input properties of abnormal giant- and control-like principal cells were examined
in FCD type IIB patients. Surgical samples were compared to controls from the same
cortical regions with short postmortem intervals. For the study, six subjects were
selected/each group. The perisomatic inhibitory terminals were quantified in parvalbumin
and neuronal nuclei double immunostained sections using a confocal fluorescent microscope.
The perisomatic input of giant neurons was extremely abundant, whereas control-like
cells of the same samples had sparse inputs. A comparison of pooled data shows that
the number of parvalbumin-immunopositive perisomatic terminals contacting principal
cells was significantly larger in epileptic cases. The analysis showed some heterogeneity
among epileptic samples. However, five out of six cases had significantly increased
perisomatic input. Parameters of the control cells were homogenous. The reorganization
of the perisomatic inhibitory system may increase the probability of seizure activity
and might be a general mechanism of abnormal network activity.