“…Both central and peripheral levels of SP are elevated in some depressed patients (Bondy et al, 2003; Geracioti et al, 2006; Rimón et al, 1984), and successful antidepressant activity of several classes of antidepressants has been associated with a reduction in these levels (Bondy et al, 2003; Husum et al, 2001; Lieb et al, 2004; Olsson et al, 2004; Shirayama et al, 1996). In addition, antidepressant treatment has been shown to downregulate NK-1r expression in the brain (Herpfer, Fiebich, et al, 2005) and may attenuate stress-induced increases in SP levels in some brain regions (described in Ebner & Singewald, 2006). More general claims about the impact of antidepressants on the central SP–NK-1r system are difficult to make because the data are inconsistent (see Ebner & Singewald, 2006, for a review).…”