Ionic currents in retrogradely labeled trigeminothalamic neurons in slices of rat medulla

We have recorded the ionic currents of identified trigeminothalamic neurons in medulla slices in vitro. Trigeminothalamic cells were first retrogradely labeled by injecting fluorescent latex microspheres in the thalamus of a 7- to 10-day-old rat. Two days later, thin slices (80-100 microns) were prepared from the lower medulla of the injected rat. Whole cell recordings were performed on the labeled cells located in the spinal trigeminal nucleus caudalis using the patch clamp technique. The voltage dependent inward sodium, inward calcium and outward potassium currents are qualitatively similar to those obtained from the enzymatically dissociated trigeminothalamic neurons. Successful application of this thin slice method opens the opportunity of studying synaptic circuitry in the trigeminothalamic system.