1 Introduction 1 1 Szallasi and Blumberg, 1999; Szolcsanyi, 2004 Caterina et al. (1997) Tominaga et al., 1998; Zygmunt et al., 1999; Caterina et al., 1999; Smart et al., 2000 Balla et al., 2001; Lundbaek et al., 2005; Kofalvi et al., 2006 1 1 1 Acs et al., 1996; Mezey et al., 2000; Roberts et al., 2004; Toth et al., 2005; Cristino et al., 2006 1 Roberts et al., 2004; Cristino et al., 2006 1 1 1 Al-Hayani et al., 2001; Huang et al., 2002 1 1 Sasamura et al., 1998; Hájos and Freund, 2002; Marinelli et al., 2002, 2003; Xing and Li, 2007 1 1 2 Experimental procedures 1 Davis et al., 2000 1 2 Fig. 1 3 2 2 2 4 2 2 3 2 2 2 4 2 http://www.superte.ch U E 3 Results 1 1 Hájos and Freund, 2002 n p Fig. 2 1 n p Fig. 2 1 p 1 n p Fig. 3 n p 1 n p Fig. 3 n p 1 1 n p n p n p 1 n p Fig. 4 n p Fig. 4 1 n p Fig. 4 n p Fig. 4 1 p 1 4 Discussion 1 Hájos and Freund, 2002 1 Dray et al., 1989; Docherty et al., 1991; Caterina et al., 1997 1 Al-Hayani et al., 2001; Marinelli et al., 2003 Kofalvi et al. (2003) Hájos and Freund, 2002 Kofalvi et al., 2003 + 2+ Kofalvi et al., 2006 2+ 2+ Hájos and Freund, 2002; Marinelli et al., 2002, 2003 Marinelli et al., 2003 2+ 1 Cristino et al., 2006 1 1 Caterina et al., 1997; Gavva et al., 2007; Liu et al., 2007