Abstract
Making patch-clamp recordings in vivo under direct visual control is highly desirable since it allows specific cell types to be targeted reliably. Previous methods for targeted patching (Margrie et al., 2003) require neurons to be fluorescently labeled, either by use of transgenic animals or viral transfection.We have developed a new approach for making targeted patch-clamp recordings from unlabeled neurons in vivo visualized using two-photon microscopy. The method involves using a patch electrode to perfuse the extracellular space surrounding the neuron of interest with a fluorescent dye, thus allowing the neuron to be visualized as a negative image and identified on the basis of its somatodendritic structure. The same electrode can then be placed on the neuron under visual control to allow gigaseal formation. This approach, which resembles that used by Euler et al. (2002) to target amacrine cells in whole-mount retina, thus offers the prospect of targeted recording and labeling of single neurons in the intact native mammalian brain without the need to pre-label neuronal populations.We demonstrate the reliability and versatility of the method using recordings from principal neurons and interneurons in barrel cortex and cerebellum in adult mice and rats anaesthetized with ketamine/xylazine or urethane. We also show that the method can be used for targeted electroporation in single identified neurons in vivo. [J Physiol Sci. 2007;57 Suppl:S27]
