Research

Neural control of the heart is under the influence of the sympathetic and the parasympathetic divisions of the autonomic nervous system. Parasympathetic control of the heart involves the convergence and integration of projections from the vagal motor nuclei within the intracardiac ganglia (ICG). ICG are interconnected clusters of neurones located throughout the atrial epicardium and interatrial septum. They send their projections to discrete regions of the heart. The final pattern of discharge in these neurones regulates chronotropic, dromotropic and inotropic elements of cardiac function.
It is clear that the electrophysiological properties of these neurones are not static, but alter during postnatal development. For example, changes in the expression of ion and receptor channels underpin the increase in diversity of neurone properties observed between the neonate and adult ICG (1,2) .
There is good evidence for interaction between sympathetic and parasympathetic efferent drive in the ICG to regulate cardiac function. An imbalance in the sympathetic and parasympathetic regulation of the heart is a feature of heart failure.
Impaired parasympathetic control of the heart is a powerful independent negatively prognostic predictor of arrhythmia and also a characteristic of myocardial infarction and heart failure

We have investigated the action of simulated ischaemia on synaptic function and the integrating properties of intracardiac ganglion neurones (5,6).
Numerous mechanisms for modulation of neurotransmission within the intracardiac ganglia have been identified, yet little is known about the contribution of these mechanisms to synaptic transmission in the ganglia. Currently we are using a combination of electrophysiological recording techniques and Ca2+ imaging to ascertain whether neuroactive agents released from neurones within or converging on the ICG alter ganglionic transmission and modify the neuronal excitability and encoding properties of the postganglionic neurone.
In addition, I continue to maintain an interest in the functional roles of potassium channels (3, 4)

Confocal images showing the distribution and density of synaptic boutons in the ICG. An adult ICG neurone was dye labelled with Lucifer yellow (green) and immunostained with synaptophysin to show the synaptic boutons (purple) in close apposition with the labelled neurone.
Superimposed, a single synaptically evoked action potential recorded from the same neurone.

Teaching