Figure 2. Schematic representation of the Me5 drawn from coronal sections of the brainstem, -9.1 mm posterior to bregma. An asterisk indicates the stimulated site. 4V, fourth ventricle; IRt, intermediate reticular nucleus; LC, locus coeruleus; Me5, trigeminal mesencephalic nucleus; Pr5, principal sensory trigeminal nucleus; py, pyramidal tract; sp5, spinal trigeminal tract; ts, tectospinal tract.