Thomale, U.-W. | Search bioRxiv

bioRxiv2026

Syncytial coupling of mid-capillary pericytes underlies seizure-associated electro-metabolic signaling

Disturbances of neurovascular coupling (NVC) contribute to metabolic derailment and neurological symptoms associated with epilepsy. While postictal arterial constriction can be alleviated by inhibitors of voltage gated calcium channels (VGCCs), less is knownregarding seizure-associated electrical signals in higher-order capillaries and their role in determining pericyte tone during seizures. Here we investigated electrical signaling within the ex vivo neurovascular unit (NVU) derived from rat and human brain tissue. We focused on electrical signal transduction between pericytes and endothelial cells and the potential role of VGCCs in vasomotion. Using dye coupling and paired patch-clamp recordings, we showed that morphologically heterogeneous groups of mid-capillary pericytes build a functional syncytium with endothelial cells. Coupling was asymmetric, allowing for directed propagation of electrical signals. Regardless of their morphology, mid-capillary pericytes responded with depolarization and constriction to metabotropic receptor (GPCR) activation (by thromboxane, norepinephrine and UDP-glucose). However, depolarization via the patch pipette induced neithe r Ca2+-influx nor constriction, suggesting lack of contribution of VGCCs to vasomotion. On inducing epileptiform activity, A2a adenosine receptors and inwardly rectifying potassium channels hyperpolarized the capillary syncytium, followed by repeated depolarizations due to seizure-associated potassium increase in the parenchyma. Thus, while mid-capillary pericytes are contractile, their tone does not rely on their membrane potential and VGCCs. However, syncytial coupling allows for transmission of seizure-associated hyper- and depolarizing signals to upstream feeding arterioles.

neuroscience↗

bioRxiv2025

The polyamine naphthyl-acetyl spermine trihydrochloride (NASPM) lacks specificity for Ca2+-permeable AMPA receptors and suppresses seizure like activity in human brain tissue by inhibition of NMDA receptors.

For decades, naphthyl-acetyl spermine trihydrochloride (NASPM) has been used as a selective inhibitor of calcium-permeable AMPA receptors (CP-AMPAR). In rodents, NASPM is known to suppress seizures in vivo and seizure-like events (SLE) in vitro, suggesting possible involvement of CP-AMPAR in ictogenesis and epileptogenesis. To address whether these findings can be translated to human brain, we investigated the involvement of glutamatergic receptor subclasses in SLE in human cortex ex vivo, demonstrating that glutamatergic receptor antagonists can block (NASPM and APV) or reduce (UBP302, GYKI52466, GYKI53655) SLE. Using a multimethodological approach we were able to demonstrate that both NASPM and APV inhibit human SLE by inhibition of NMDA receptors. Our results further show that the inhibitory effect of NASPM on NMDA receptors is sufficient to explain its inhibition of seizure like activity, rather than its action on CP-AMPA receptors. Thus, our findings challenge previous knowledge on the use of NASPM as a specific CP-AMPAR inhibitor. Some phenomena previously attributed to CP-AMPAR, may need to be re-examined more closely. Overall, our study raises awareness about potential pitfalls in the use of existing pharmacological agents and sets a new paradigm for the use of NASPM in neuroscience research while questioning its therapeutic potential in a clinical context.

neuroscience↗