“…In fact, the locus coeruleus is involved in many biological functions (Ryu et al, 1999;Almeida et al, 2004;Kishi et al, 2006), and exerts a key-role in antinociception (Mokha et al, 1985;Freitas et al, 2005;Voisin et al, 2005). The involvement of serotonergic and noradrenergic pathways and reticular formation nuclei in the antinociception is reported by works using many noxious stimulus-based tests, such as the tail-flick and hot plate tests (Sawynok and Reid, 1987;Coimbra et al, 1992;Coimbra and Brandão, 1997;Miyase et al, 2005;Rebouças et al, 2005;Segato et al, 2005;Freitas et al, 2005;Kishi et al, 2006;Coimbra et al, 2006), paw-withdrawal latencies (Tsuruoka and Willis, 1996), formalin test (Sajedianfard et al, 2005), percutaneous electrical foot shock (Hirata and Aston-Jones, 1994) and the electrical stimulation of dental pulp test in rats (Couto et al, 1998;Voisin et al, 2005).…”