| Title | Scratching behavior and Fos expression in superficial dorsal horn elicited by protease-activated receptor agonists and other itch mediators in mice. | | Author(s) | Akiyama T, Merrill A, Zanotto K, Iodi Carstens M, Carstens E | | Institution | University of California, Davis. | | Source | J Pharmacol Exp Ther 2009 Mar 17. | | Abstract | The protease-activated receptors -2 and -4 are implicated in non-histaminergic itch. We investigated dose-dependency, tachyphylaxis and cross-tachyphylaxis of itch-associated scratching elicited by intradermal (id) injections of PAR-2 and -4 agonists, 5-HT and histamine in ICR mice, as well as micro-opioid modulation of PAR-2 agonist-evoked scratching. Each agent elicited dose-related increases in scratch bouts. Scratching elicited by the PAR-4 agonist and histamine both exhibited significant tachyphylaxis but no cross-tachyphylaxis with each other. Scratching evoked by 5-HT did not exhibit significant tachyphylaxis but did exhibit significant cross-tachyphylaxis to scratching evoked by the PAR-2 and PAR-4 agonists and histamine. Naltrexone and high-dose morphine (10 mg/kg) attenuated PAR-2 agonist-evoked scratching, while lower-dose morphine (1 mg/kg) had no effect. High-dose morphine also significantly increased circling behavior which may have interfered with scratching. The PAR-2 agonist and 5-HT produced overlapping distributions of Fos-like immunoreactivity in the superficial dorsal horn. These results indicate that PAR-2 and PAR-4 agonists, histamine and 5-HT elicit itch-related scratching and activate superficial dorsal horn neurons that may participate in scratch reflex and ascending itch-signaling pathways. | | Language | ENG | | Pub Type(s) | JOURNAL ARTICLE
| | PubMed ID | 19293390 |
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