Camera lucida drawings indicating the pattern of Fos-LI produced in the lower brainstem after acute TMJ stimulation by 20% mustard oil (MO) in a HE2-treated female rat. Left side is ipsilateral to the TMJ stimulus and boxes indicate regions that were quantified bilaterally for Fos-LI. Approximate rostrocaudal levels caudal to obex: upper panel, 0.5 mm; middle panel, 3.0 mm; lower panel, 5 mm. Abbreviations: dPa5, dorsal paratrigeminal region; Vc, trigeminal subnucleus caudalis; Vi/Vcvl, ventrolateral portion of trigeminal subnucleus interpolaris/caudalis transition region; Vc/C1-2, spinomedullary junction region. Each dot = 1 Fos-positive neuron. Calibration = 0.5 mm.