Figure 4: Double immunofluorescence laser scanning confocal microscopy images demonstrating the location of nicotine (NIC), and nicotine pyrrolidine methiodide (NIC-PM) induced c-Fos immunoreactive (IR) neurons with respect to tyrosine hydroxylase (TH) IR cells of dorsal raphe nucleus (DR). Panels A–C: Control data demonstrating effects of acute intraperitoneal injection of physiological saline (PS) on c-Fos activation of TH IR cells in DR. Panels D-F and G-I : NIC and NIC-PM data respectively, showing c-Fos IR cells (D, G), TH IR cells (E,H) and merge images of c-Fos with TH IR cells (F, I) in DR. Arrows point to areas magnified in photomicrographs.