While it is commonly known that epilepsy can cause loss of consciousness and disabling seizures, it is less well known that it can cause significant heart problems. A seizure can be potentially dangerous, triggering the nerves in the brainstem to increase blood pressure and heart rate and even cause dangerous heart rhythms.
These cardiovascular effects are due to the mass activation of the autonomic nervous system, the sub-conscious automatic nerve network which controls breathing and circulation.
The good news, as described in a recent publication in the highly-esteemed Journal of Neuroscience, is that our High Blood Pressure Group has been able to demonstrate the powerful cardio-protective properties of microglia, the brain's immune cells.
The study found that by inhibiting microglia after a seizure, they were able to generate a significantly greater increase in sympathetic nerve activity, and subsequently more severe cardiovascular effects.
In time, this means that we may be able to reduce the risk that an epileptic seizure will trigger a deadly heart attack.
These findings suggest that microglia are critical in soothing this increased excitation during seizures.
Professor Paul Pilowsky, group leader of the High Blood Pressure Group, explains how this is achieved, “Microglia are able to soothe this overactivity by trimming the synaptic spines located on the dendrites of excited neurons.”
“We are quite excited to have discovered that microglia perform a normal physiological role, in keeping excited cells in a state where they can respond effectively to further stimuli.”
The study also found that a brain chemical called PACAP, which is released from neurons when they are active, is key to the communication process and works in concert with the microglia to dampen the sympathetic nerve response and protect the heart during seizures.
This deeper understanding of the role of microglia and PACAP during seizures adds to what is already known about the delicate interplay between the brain, heart and immune system in maintaining a healthy heart.
Ultimately, these findings may lead to new therapies to prevent cardiovascular complications from epilepsy and other diseases which share an elevated sympathetic response, such as sleep apnoea and essential hypertension.