Phosphoinositides (PI) have been shown to participate in the regulation of a number of cellular processes. Among these the modulation of endo-and exocytosis and the activity of ion channels are of particular importance to neurons. However, the extent to which changes in PI concentration in the cell membrane play a role in the physiological regulation of neuronal excitability and synaptic efficacy has not been addressed. Thus, we aim to analyze receptor mediated phosphoinositide dynamics in neurons in their native environment, with the focus on phosphatidylinositol 4,5-biphosphate (PIP₂). To this day, most of the studies on the impact of phosphoinositides on neuronal processes have employed protein expression in heterologous expression systems or analysis in isolated neurons. The modulation of PI membrane concentration is frequently achieved by application of PI liposomes, antibodies or up and down regulation of specific lipid kinases, phosphatases and lipases. By these means a number of ion channels has been found to depend on PIP₂. What is still lacking is convincing evidence how this dependency actually affects neuronal behavior under more natural conditions. To approach this problem, we set out to visualize receptor mediated PIP₂ dynamics in acute hippocampal slices after Oxotremorine-M application. There, activation of CA1 pyramidal muscarinic acetylcholine receptors induces PIP₂ depletion via Gaq-proteins and subsequent involvement of phospholipase C. Monitoring of PIP₂ localization was achieved by confocal imaging of specific PI-binding domains (e.g. Tubby-C domain) coupled to fluorescent proteins. To express these probes in vivo, we used lentiviral vectors stereotactically injected into the hippocampal region of rats. Successful expression allowed monitoring of PIP₂ dynamics in acute hippocampal brain slices. Further refinement of the method will help to assess the physiological relevance of PI dynamics in neurons. Supported by DFG: SFB 593, TPA12.