The technical assistance of Mrs. of mice injected with acetic acid and the increase was attenuated by pretreatment with amylin (10 g, i.t.). Collectively, our result demonstrates that irAMY is expressed in dorsal root ganglion neurons with their cell processes projecting to the superficial layers of the dorsal horn, and that the peptide by interacting with amylin receptors in the spinal cord may be antinociceptive. Keywords:antinociception, dorsal root ganglia, intrathecal, c-fos, amylin receptor == Introduction == Amylin, a 37 amino acid peptide secreted from pancreatic -cells Apaziquone upon stimulation by meal or glucose (Cooper et al., 1987; Westermark et al., 1987), is a member of the calcitonin family which includes calcitonin (CT), calcitonin gene-related peptide (CGRP) and adrenomedullin (AM) (Muff et al., 2004). Amylin-like immunoreactivity (irAMY) has been reported in the gut (Mulder et al., 1994), osteoblast (Gilbey et al., 1991) and central nervous system of humans and rats (Skofitsch et al., 1995;D’Este et al., 2000). Amylin is abundantly expressed in rat dorsal root ganglion cells, some of which contain substance P and pituitary adenylate cyclase-activating polypeptide (Mulder et al., 1995). Further, irAMY and CGRP-immunoreactivity overlaps in Apaziquone the motor nuclei of the hindbrain and spinal cord (Skofitsch et al., 1995;Gebre-Medhin et al., 1998). Amylin is structurally similar to both salmon CT (sCT, about 30% homology) and CGRP (about 50% homology) (van Rossum et al., 1997). Similar to CGRP receptors, amylin receptors are heterodimeric complex of calcitonin receptor (CTR) and receptor activity modifying proteins (RAMP) (Christopoulos et al., 1999). High affinity amylin binding sites are located in many regions of the rat and monkey brains; including the hypothalamus, nucleus accumbens, dorsal raphe and area postrema (Stridsberg et al., 1993;Sexton et al., 1994;Paxinos et al., 2004). Little is known relative to the function of amylin in the mammalian nervous system. Amylin has been proposed as an anorexigen affecting the gastrointestinal system and ingestive behavior (Riediger et al., 2001;Young, 2005;Edelman et al., 2008). The peptide has also been shown to exert anti-inflammatory activity (Clementi et al., 1995) and protect gastric mucosa in various ulcer models (Samonina et al., 2004). Variable results have been reported relative to its involvement in nociception. Apaziquone For example, central administration of amylin failed to induce antinociception (Bouali et al., 1995;Sibilia et al., 2000), while peripheral administration (subcutaneous or Apaziquone intraperitoneal) produced antinociception (Young, 1997). In the pain signaling pathways, the immediate early gene c-fos is promptly expressed in neurons in response to a painful stimulus (Sagar et al., 1988). Several Rabbit polyclonal to HGD reports have shown that the expression of c-fos mRNA or immunoreactivity is up-regulated in the spinal cord following noxious visceral stimulation (Rodella et al., 1998;de los Santos-Arteaga et al., 2003;Lee and Seo, 2008). In contrast, expression of c-fos in the spinal cord was attenuated by pretreatment of analgesia (Lee and Seo, 2008). Thus, expression of c-fos mRNA or protein can be used as a marker of neurons activated by pain sensation (Harris, 1998). In this study, results from a multidisciplinary approach including immunohistochemistry, molecular biology and in vivo pharmacology, support the hypothesis that amylin is antinociceptive in an acetic acid-induced writhing mouse model. == EXPERIMENTAL PROCEDURES == == Experimental Animals == Adult male ICR mice (Ace Animal Inc., Boyertown, PA) weighing 25-30g were used in this study. Experimental protocols were reviewed and approved by the Temple University Institutional Animal Care and Use Committee, in accordance with the 1996 NIH Guide for the Care and.