Cellular signalling mechanisms in the developing visual cortex

• Applicant: Professor Dr. Knut Holthoff
• Subject Area: Molecular Biology and Physiology of Neurons and Glial Cells
• Term: from 2007 to 2011
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 43578342

Short after eye opening, a fraction of neurons in layer 2/3 of the mouse visual cortex responds to specific features of the visual stimuli. The general goal of the proposed project is to identify the cellular signaling mechanisms of these feature-specific neurons in the developing visual cortex in vivo. In a first step by using fast confocal calcium imaging, we will characterize the dendritic signaling of cortical layer 2/3 cells in vitro. This analysis will cover synaptically induced calcium signaling in dendrites and dendritic spines. For the in vivo experiments we will first establish somatic and dendritic calcium imaging approach involving a genetically encoded calcium indicators and the loading of individual cells in vivo by using whole cell patch loading or electroporation. These techniques will be used in a next set of experiments to analyze the molecular mechanisms of calcium signaling of layer 2/3 pyramidal neurons upon sensory stimulation in vivo. The calcium imaging in vivo will be performed with a recently developed real-time two-photon imaging device. In a next set of experiments, we will analyze the calcium signaling of GABAergic interneurons upon stimulation in vitro and in vivo. We will use transgenic animals, in which somatostatin-positive cells are labeled with the enhanced green fluorescent protein. To determine the electrophysiological properties of feature-selective cells, we will perform whole cell patch-clamp recordings in vivo. In these experiments, individual neurons will be identified first as feature-specific using somatic calcium imaging of bulk loaded cells. The cells of interest will then be patched under optical control and electrophysiological responses will be recorded upon sensory stimulation. Finally, we will test whether the feature-selectivity in layer 2/3 cells can be modified in an activity-dependent manner.

• DFG Programme: Research Grants
• Participating Person: Professor Dr. Arthur Konnerth