Figure 1. Sagittal views of the pontine brain stem. (A) Schematic diagram indicating that cholinergic LDT neurons send projections to the cholinoceptive mPRF. The LDT-mPRF relationship is simplified here for illustrative purposes. LDT connectivity is complex, including LDT reciprocal connections and projections to the thalamus and to the contralateral mPRF (reviewed in [9]). Cresyl violet-stained sections of the brain stem illustrate lesions used to confirm dialysis probe placement in the LDT (B) and mPRF (C). In B and C, the black arrow marks the tip of the dialysis probe lesion in the LDT and mPRF, respectively; calibration bars at lower right = 1 mm. Approximate lateralities are 1.2 mm for LDT (B) and 1.6 mm for mPRF (C). 6N = abducens nerve; 7G = genu of facial nerve; PAG = periaqueductal gray; TB = trapezoid body.