Juxtasomal loose-patch recordings in awake, head-fixed rats to study the link between structure and function of individual neurons

Abstract

The loose-patch juxtasomal recording method can be applied to characterize action potential spiking from single units in the extracellular configuration and includes the attractive option of labeling the neuron for post hoc identification and reconstruction. This ensures “observing without disturbing” (Schubert, J Physiol 581(Pt 1):5, 2007) since the juxtasomal loose-patch recording does not involve breaking into the neuron and modifying its intracellular environment until after all physiological parameters have been obtained. The fundamental difference with extracellular recordings is therefore that juxtasomal recordings generate a direct link between physiological properties and cellular morphology. The necessary step for juxtasomal labeling involves physical interaction between the recording patch pipette and somatic membrane to create a loose-seal patch-clamp recording (hence: juxtasomal) and electroporation for label dialysis (Joshi and Hawken, J Neurosci Methods 156(1–2):37–49, 2006; Pinault, J Neurosci Methods 65(2):113–136, 1996). Next, post hoc histology is performed to reveal cell-type identity and optionally to digitally reconstruct the recorded neuron. In this chapter, I will describe the basic experimental procedures to obtain juxtasomal recordings in primary somatosensory cortex of awake, head-fixed rats and illustrate the information content of these experiments.