Candidate genes validated using in situ hybridization. (a, c) gfi1b and her15 are expressed in ventricular zones throughout the brain, including in the midline of the telencephalon. (b, d) Upon chronic amphetamine administration, this expression is visibly down-regulated, and this throughout the brain (see also Additional data file 8a-d). Upon amphetamine administration, (f, h) the expression of foxg1 and lhx8 is reduced in the parvocellular preoptic nucleus, posterior part (PPp) (foxg1 and lhx8) and in the ventral zone of the periventricular hypothalamus (Hv) (foxg1), when compared to (e, g) the brains of animals injected with a saline solution. The expression pattern of these genes remains unchanged in other brain areas upon amphetamine administration (Additional data file 8e-h). Scale bars = 100 μm in all panels. D = dorsal telencephalic area; Hv = ventral zone of the periventricular hypothalamus; mt = midline of the telencephalon; PPp = parvocellular preoptic nucleus, posterior part; V = ventral telencephalic area; VL = ventrolateral thalamic nucleus.