Cre expression directed to dopaminergic (A), serotonergic (B), and cholinergic (C) neurons in BAC-Cre transgenic mouse lines. A, Dopaminergic neurons are labeled in a Th BAC-Cre transgenic line with Cre expression localized in neurons in the midbrain substantia nigra pars compacta (Th BAC-CRE; green), which colocalize with Th-IR. There is a nearly complete overlap of TH Cre-driven EGFP labeling and Th-IR (insets). B, In a serotonin transporter (Slca4) BAC-Cre transgenic line, Cre is directed to serotonergic neurons in the dorsal raphe nucleus in the dorsal midbrain, which coexpress serotonin-synthesizing enzyme, tryptophan hydroxylase-IR. Insets, There is a nearly complete overlap of Slca4 Cre-driven EGFP labeling and tryptophan hydroxylase-IR in neurons in the dorsal raphe. C, In a Chat BAC-Cre transgenic line, labeled neurons in the basal forebrain coexpress Chat immunoreactivity (ChAT-IR).