Cumulative and temporal analysis of multiple co-released neurotransmitters.

Single nerve cells contain multiple different types of signalling molecules. Different combinations of signalling molecules (neurotransmitters) are released by the nerve cells to allow the nervous system to adapt to changes in environmental cues.

This process is known as plasticity. As we age our nervous systems become less plastic but how the ageing process affects the release of neurotransmitters is not understood. We have chosen to study this process in the nervous system of the pond snail. Snails have a lifespan of about 1 year making them ideal for ageing studies. Their nervous system consists of large reproducibly identifiable nerve cells allowing the studies to be performed on an identified nerve cell across the lifecourse of the snail. We have chosen to explore the release of neurotransmitters from a cell that contains examples of the three main classes of signalling molecule, namely a classical transmitter (serotonin) and gaseous transmitter (nitric oxide) and a peptide transmitter (myomodulin).

We have used carbon fibre microelectrodes to study release of the monoamine neurotransmitter serotonin (5-HT) and the gaseous transmitter nitric oxide (NO) in intact central nervous system of the water snail, Lymnaea stagnalis.


Analysis of spontaneous vesicular release of 5-HT and depolarisation-induced release of NO reveals significant differences with ageing. Specifically, we show that the amount of 5-HT released per event is greater in old cells although the frequency of release events is slower, with no overall change in the amount of 5-HT released per unit time. With nitric oxide the total amount of NO released was also not altered with increasing age but the release was slower to reach a maximum.

In summary this grant showed that while the total amount of both neurotransmitter released per unit time was not altered by the ageing process the dynamics of release were changed.