Hippocampal sclerosis is a thickening and hardening of the brain tissue in the hippocampus. It is a very common feature of TLE. This sort of epilepsy is frequently not treatable with AEDs, but responds well to surgery. Dr Nicholas Barnes of the University of Birmingham has been awarded £45,316 over two years to look at brain tissue from patients who have had surgery for TLE caused by hippocampal sclerosis. These patients appear to have a different distribution of some types of neurotransmitter receptors in the part of the brain where the seizures occur.
Neurotransmitters are molecules which carry information from one neurone to the next. They fall into two broad classes: inhibitory, which slow down neurone activity, and excitatory, which speed it up. Each type of neurotransmitter has its own receptor, and some have more than one type of receptor. Receptors are protein complexes in the wall of a neurone. The speed at which a message can be transmitted through the brain depends both on the number of neurotransmitter molecules and also on the number of receptors. (Think of the neurotransmitters as letters and the receptors as dedicated postboxes, each only taking a specific size of letter or parcel. Whether your correspondent gets your message depends both on the number of letters you write and also on the number of postboxes you can find for them.) This has implications for epilepsy as a seizure happens when far too many messages are sent, swamping the brain’s circuits. Too many excitatory neurotransmitters released or too many of their receptors available can make this happen more easily.
Dr Barnes, in his project entitled “Neurotransmitter receptor distribution in patients with TLE due to hippocampal sclerosis“, will try to quantify exactly which types of brain cell contain the receptors and how and why (on a molecular and cellular level) the distribution of receptors changes. The hope is that it will then be possible to develop new AEDs which target these receptors.
This is one of five grants made by the Epilepsy Research Foundation (now Epilepsy Research UK) in 2005. Read about the other grants from 2005 here