Kristina Petrova Dimintiyanova: "Plasticity of motoneuron excitable domains"

PhD student, Meehan Lab

Abstract: The axon initial segment (AIS) is the site of action potential generation in most neurons, and the biophysical properties of this structure regulate the intrinsic excitability of the cell. Recently it has been shown that the AIS is a highly plastic structure. The size and location of the AIS are highly tuned to the size of the neuron and the extent of the dendritic tree. These properties can be re-tuned in response to changes in neuronal activity. Change in size and location of AISs segments have been shown in vitro and in the developing auditory system. Understanding the effects of the AIS plasticity in the adult system in vivo, however, can be challenging due to the large number of targets that most neurons have. Therefore, in our lab we are focusing on using the motoneuron to study the plasticity of its AIS in the adult in vivo. The motoneuron is a perfect model system to study such phenomenon because it has a single identifiable target – the muscle, and any changes in motoneurons excitability have a direct readout on the activity of the muscle. Our studies show that the AIS of adult motoneurons is highly plastic and rapidly responds to changes in the neuronal environment which occur with injury or disease. Furthermore, we show that this plasticity is implicated in a number of disorders of the motor system, and could potentially help to explain the abnormal excitability observed in these disorders.