Electrophysiological setup for recording GnRH neurons in vivo. A, The sphenoid bone was exposed by a transpharyngeal surgical approach. B, Part of the sphenoid bone (edge outlined in black) was removed (stippled area), and a hole was drilled to expose the optic chiasm (OC) beneath. This was removed to visualize the ventral surface of the brain from the organum vasculosum of the lamina terminalis (OVLT) to the median eminence (ME). C, The most superficial GnRH neurons (green fluorescent cells) at the base of the brain lie close to the posterior communicating artery (pca). D, After surgical exposure, the mouse was shifted to the recording platform and a reference electrode and perfusion inflow and outflow positioned. E, The electrode (red in D) was positioned initially by alternating fluorescence wavelengths allowing the visualization of either the pipette (tetra methyl rhodamine, E1) or the targeted neuron (GFP, E2), until they were in proximity (E3; scale bar, 50 μm). When the electrode was close to the GnRH neuron, positive pressure was applied and the pipette shadow (arrow) was used for the final approach (F; scale bar, 10 μm). ON, Optic nerves; OT, optic tracts; PS, pituitary stalk; 3V, third ventricle.