GABAergic inhibitory circuitry within the intermediate layer of the superior colliculus plays an essential role in generating the premotor signals that initiate shifts in the direction of gaze. However, the spatiotemporal dynamics of this inhibition remain unclear. We will use Clomeleon, a genetically-encoded Cl- indicator, to image in real time the spatial organization of Cl- dependent synaptic inhibition. We have produced transgenic mice that express Clomeleon in premotor cells of the intermediate layer. Clomeleon chronically expressed in these neurons is capable of responding to Cl- fluxes associated with activation of GABAA receptors. We propose to use these Clomeleon mice to determine whether Clomeleon is sufficiently sensitive to detect the changes in [Cl-]i that are generated in the premotor cells by stimulation of GABAergic pathways. To test the hypothesis that activation of premotor cells in a region that commands gaze shifts in one direction inhibits the ? activity of cells in other regions that would command competing gaze shifts toward stimuli in other directions, we will use Clomeleon to visualize the spatiotemporal distribution of inhibition throughout the intermediate layer that is evoked by activity within one region of this layer's spatial map of gaze vectors. This approach of functional imaging CI-mediated inhibition potentially can be applied to the study of inhibitory circuitry in any brain area. ? ? ?
