Controlling learning and epilepsy together

Effects of Minocycline on Cognitive Impairment, Hippocampal Inflammatory Response, and Hippocampal Alzheimer’s Related Proteins in Aged Rats after Propofol Anesthesia

The aim of this study was to evaluate the effect of minocycline preadministration on cognitive dysfunction, hippocampal inflammatory response, and hippocampal senile dementia-related proteins induced by propofol anesthesia in aged rats. Sixty male SD rats, aged 20 months and weighing 340-410 g, were randomly divided into three groups: normal saline (NC) group, propofol group (prop), and minocycline (M) group. Prop group rats were injected intraperitoneally with 100 mg/kg propofol. The rats in group M were injected intraperitoneally with 50 mg/kg minocycline 30 minutes before injection of 100 mg/kg propofol, and the rest were the same as prop group. The rats in NC group were received intraperitoneal injection of the same amount of normal saline. The results indicated that compared with group C, the expressions of GSK-3β, acetyl-NF-κB (Lys310), Tau, and Amlyoid-beta were upregulated, the levels of TNF-α, IL-1β, and IL-6 were increased, the escape incubation period was prolonged, and the exploration time was shortened in prop group, while the expression of GSK-3β, acetyl-NF-κB (Lys310), Tau, and Amlyoid-beta in minocycline group was downregulated, the levels of TNF-α, IL-1β, and IL-6 were decreased, the escape incubation period was shortened, and the exploration time was shortened. In conclusion, preadministration of minocycline can improve cognitive impairment induced by propofol anesthesia in aged rats, and its mechanism of action may be related to minocycline inhibiting hippocampal inflammatory reaction and downregulating the expression of GSK-3β, acetyl-NF-κB (Lys310), Tau, and Amlyoid-beta proteins in hippocampus.

Toward Understanding the Diverse Roles of Perisomatic Interneurons in Epilepsy

Epileptic seizures are associated with excessive neuronal spiking. Perisomatic γ-aminobutyric acid (GABA)ergic interneurons specifically innervate the subcellular domains of postsynaptic excitatory cells that are critical for spike generation. With a revolution in transcriptomics-based cell taxonomy driving the development of novel transgenic mouse lines, selectively monitoring and modulating previously elusive interneuron types is becoming increasingly feasible. Emerging evidence suggests that the three types of hippocampal perisomatic interneurons, axo-axonic cells, along with parvalbumin- and cholecystokinin-expressing basket cells, each follow unique activity patterns in vivo, suggesting distinctive roles in regulating epileptic networks.

Deletion of FGF9 in GABAergic neurons causes epilepsy

Fibroblast growth factor 9 (FGF9) has long been assumed to modulate multiple biological processes, yet very little is known about the impact of FGF9 on neurodevelopment. Herein, we found that loss of Fgf9 in olig1 progenitor cells induced epilepsy in mice, with pathological changes in the cortex. Then depleting Fgf9 in different neural populations revealed that epilepsy was associated with GABAergic neurons. Fgf9 CKO in GABAergic neuron (CKOVGAT) mice exhibited not only the most severe seizures, but also the most severe growth retardation and highest mortality. Fgf9 deletion in CKOVGAT mice caused neuronal apoptosis and decreased GABA expression, leading to a GABA/Glu imbalance and epilepsy. The adenylate cyclase/cyclic AMP and ERK signaling pathways were activated in this process. Recombinant FGF9 proteoliposomes could significantly decrease the number of seizures. Furthermore, the decrease of FGF9 was commonly observed in serum of epileptic patients, especially those with focal seizures. Thus, FGF9 plays essential roles in GABAergic neuron survival and epilepsy pathology, which could serve as a new target for the treatment of epilepsy.

Region-specific differences and areal interactions underlying transitions in epileptiform activity

Key points

Local neocortical and hippocampal territories show different and sterotypical patterns of acutely evolving, epileptiform activity.

Neocortical and entorhinal networks show tonic–clonic‐like events, but the main hippocampal territories do not, unless it is relayed from the other areas.

Transitions in the pattern of locally recorded epileptiform activity can be indicative of a shift in the source of pathological activity, and may spread through both synaptic and non‐synaptic means.

Hippocampal epileptiform activity is promoted by 4‐aminopyridine and inhibited by GABA_B receptor agonists, and appears far more sensitive to these drugs than neocortical activity.

These signature features of local epileptiform activity can provide useful insight into the primary source of ictal activity, aiding both experimental and clinical investigation.

Abstract

Understanding the nature of epileptic state transitions remains a major goal for epilepsy research. Simple in vitro models offer unique experimental opportunities that we exploit to show that such transitions can arise from shifts in the ictal source of the activity. These transitions reflect the fact that cortical territories differ both in the type of epileptiform activity they can sustain and in their susceptibility to drug manipulation. In the zero‐Mg²⁺ model, the earliest epileptiform activity is restricted to neocortical and entorhinal networks. Hippocampal bursting only starts much later, and triggers a marked transition in neo‐/entorhinal cortical activity. Thereafter, the hippocampal activity acts as a pacemaker, entraining the other territories to their discharge pattern. This entrainment persists following transection of the major axonal pathways between hippocampus and cortex, indicating that it can be mediated through a non‐synaptic route. Neuronal discharges are associated with large rises in extracellular [K⁺], but we show that these are very localized, and therefore are not the means of entraining distant cortical areas. We conclude instead that the entrainment occurs through weak field effects distant from the pacemaker, but which are highly effective at recruiting other brain territories that are already hyperexcitable. The hippocampal epileptiform activity appears unusually susceptible to drugs that impact on K⁺ conductances. These findings demonstrate that the local circuitry gives rise to stereotypical epileptic activity patterns, but these are also influenced by both synaptic and non‐synaptic long‐range effects. Our results have important implications for our understanding of epileptic propagation and anti‐epileptic drug action.

Local neocortical and hippocampal territories show different and sterotypical patterns of acutely evolving, epileptiform activity.

Neocortical and entorhinal networks show tonic–clonic‐like events, but the main hippocampal territories do not, unless it is relayed from the other areas.

Transitions in the pattern of locally recorded epileptiform activity can be indicative of a shift in the source of pathological activity, and may spread through both synaptic and non‐synaptic means.

Hippocampal epileptiform activity is promoted by 4‐aminopyridine and inhibited by GABA_B receptor agonists, and appears far more sensitive to these drugs than neocortical activity.

These signature features of local epileptiform activity can provide useful insight into the primary source of ictal activity, aiding both experimental and clinical investigation.