Fig. 1. Histologic confirmation of dialysis sites. (  A ) Sagittal schematic view of the rat brain illustrating the anatomical relationship between the prefrontal cortex (PrL) and substantia innominata (SI). The dialysis probe placed in the substantia innominata was used to deliver drugs. The probe placed in the prefrontal cortex was used to collect acetylcholine (ACh). The  arrow on each histologic section indicates a microdialysis site localized to the prefrontal cortex (  B ) and substantia innominata (  C ). Drawings of sagittal and coronal rat brain sections were modified from a stereotaxic atlas.  22 The anterior–posterior axis coordinate is indicated in millimeters relative to bregma at the bottom of each coronal drawing. The  calibration bar at lower right applies to all sections in  B and  C . Filled circles localize the most ventral point of 18 dialysis sites in the prefrontal cortex (  B ) and 18 dialysis sites in the substantia innominata (  C ). Overlapping dialysis sites from different animals are represented by a  single filled circle . 3V = third ventricle; CA3 = hippocampus; Cg1 = cingulate cortex; fmi = forceps minor of the corpus callosum; ic = internal capsule; IL = infralimbic cortex (part of the prefrontal cortex); LH = lateral hypothalamus; M1 and M2 = motor cortex; PrL = prelimbic cortex (part of the prefrontal cortex); SO = supraoptic nucleus.