Plasticity and function of backpropagating Action Potential mediated calcium signals in dendritic spines

• Applicant: Privatdozent Dr. Friedrich Johenning
• Subject Area: Molecular Biology and Physiology of Neurons and Glial Cells
• Term: from 2012 to 2016
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 220101484

Action potentials (APs) following suprathreshold activation of neurons propagate back into the dendritic tree. Backpropagating Action Potential (bAP)-mediated depolarization of dendritic segments and adjacent spines results in voltage-gated calcium channel mediated influx into dendrites and spines. These global calcium signals activate a much larger number of spines than local synaptically mediated calcium transients, but their function is poorly understood. In medial entorhinal cortex layer II stellate cells, we will further examine the possibility that these (bAP)-mediated calcium transients (bAPCaTs) are self-regulatory, plastic events with an impact on synaptic transmission. Mechanisms underlying induction and expression of activity-dependent boosting of bAPCaTs as well as their functional implications for synaptic transmission and circuit function will be studied. Investigations will be performed using combined whole-cell patch clamp recordings and two-photon calcium imaging with low affinity calcium indicators (fluo4FF). The low buffer capacity of this indicator will enable us to study biological effects of bAPCaTs while monitoring them. Adding Alexa 594 to the recording soution, morphological data from a separate red channel permits combination of functional data with spine morphometry. Two-photon glutamate uncaging will be applied to study the interaction of bAPCaTs and synaptic transmission in single spines.

• DFG Programme: Research Grants
• Participating Person: Professor Dr. Dietmar Schmitz