Dissection of the head cuticle and sheath of living flies for whole-cell patch-clamp recordings in the brain

Whole-cell patch-clamp recording has been applied to neurons in the central nervous system of Drosophila, allowing researchers to study the function of neurons of interest within native circuits in a genetically tractable model system. Here, we present a method to expose neurons in the fly brain for such recording. The fly is inserted into an opening in a piece of tinfoil in a recording platform and fixed in place. This immobilizes the fly's head and permits the exposed neurons to be bathed in saline above the surface of the foil, while the sensory structures (antennae, proboscis, and much of the eyes) remain dry below the surface of the foil. The tinfoil is within a well that allows external saline to be perfused over the fly, and the walls of the well adapted so the ground wire (connected to the amplifier head stage) can be securely positioned within the saline bath. Our method to construct a recording platform, presented here, makes use of materials in the laboratory. Once the fly is mounted in the platform, the head cuticle and sheath covering the brain are removed. We describe how to mount the fly and open up the head cuticle to access the mushroom body Kenyon cells (KCs), whose somata are located on the dorsal/posterior surface of the brain. To record from neuronal cell bodies located in other brain regions, the approach to mount the fly must be modified to provide consistent access to the cells of interest.