Snails set the pace in human memory loss research

The humble snail is helping scientists at the University of Sussex to explore ways of treating memory loss in humans.

Drug manufacturers are looking at ways to create a “Viagra for the brain”, which could alleviate memory loss, one of the distressing symptoms of diseases such as Alzheimer’s. Work carried out by Dr George Kemenes, Senior Fellow in the Department of Biology and Environmental Science at the University of Sussex, will hopefully help to show how such drugs could work.

Dr Kemenes says: “If you lose your memory, you lose your personality. Impaired long-term memory is a devastating consequence of a variety of diseases affecting millions of people. The knowledge obtained from this work will help us to understand, and ultimately prevent and treat, memory disorders or even enhance normal memory.”

He adds: “The aim is to find brain molecules that are crucial for the building up and maintenance of long-term memory and learning. The biggest hope is that we will then be able to find out how to operate those functions and improve the speed at which animals learn, or help them remember for longer periods of time. This would then link into drug development for humans.”

To do this, Dr Kemenes and his team, funded by a £750,000 grant from the Medical Research Council, will attempt to chemically enhance or inhibit those functions in the common pond snail.

Snails are ideal for this kind of study because humans and pond snails actually share some important characteristics, unchanged by evolution. These include the basic molecular mechanisms that control long-term memory and learning. These processes involve the activation or suppression of a protein, CREB, which is key to the formation of long-term memory, and found in species ranging from molluscs and flies to rats and man.

These responses can be tested by classic “Pavlovian” experiments that bring about a conditioned response. A snail exposed to the smell of pear drops and then food (sucrose, which they love), for example, will respond weeks later to the smell of pear drops by rhythmically moving its mouth parts in anticipation of food, even when none is provided. This shows that the snail now has a memory associating the smell of pear drops with the arrival of food – a learned and remembered response.

This “flashbulb” memory – created by just one response to stimuli, is complemented in Dr Kemenes’ research by another test, where the snail is exposed to a tickling stimulus (which it doesn’t like) before food is introduced. It takes much longer for the snail to associate this tickling with the arrival of food. Dr Kemenes will attempt to learn how to inhibit the quickly learned memory and improve the weaker, more slowly-acquired memory at molecular level by using different chemical preparations to activate or suppress the release of the memory-forming CREB protein.

Snails are also vital to this part of Dr Kemenes’ research because they have large neurons (nerve cells), which are easily identified, manipulated and observed under a microscope than mammalian brain cells, making them ideal subjects for exploring the learning and memory process at the cellular and molecular level.