Intracisternal Injection of Opioids Induces Itch-Associated Response through .MU.-Opioid Receptors in Mice.

Tohda, Chihiro; Yamaguchi, Tomomi; Kuraishi, Yasushi

doi:10.1254/jjp.74.77

Cited by 48 publications

(49 citation statements)

References 21 publications

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“…morphine on scratching. These results support previous studies indicating that mu-opioid receptors, rather than kappa-or delta-opioid receptors, mediate scratching induced by centrally administered morphine (Thomas et al, 1992;Tohda et al, 1997;Ko and Naughton, 2000;Kuraishi et al, 2000).…”

Section: Discussionsupporting

confidence: 91%

“…This inverted U-shape curve of i.c. morphine-induced scratching was also observed in mouse studies (Tohda et al, 1997;Yamaguchi et al, 1998). It might be due to general suppression of behaviors by high doses of morphine.…”

Section: Discussionmentioning

confidence: 67%

“…Therefore, observation for the bombesin groups started 2 min after drug administration. In order to distinguish scratching from grooming, scratching events were counted as those made by the hind paws (Kuraishi et al, 1995;Thomas and Hammond, 1995;Tohda et al, 1997); movements with the forepaws were counted as grooming events. A scratch was defined as one short-duration episode of scraping contact by the hind paw on the skin surface of other body parts.…”

Section: Methodsmentioning

confidence: 99%

“…Each person only observed the behaviors of one rat at any time. The range of morphine (0.0032-10μg) or bombesin (0.0032-0.32μg) doses was chosen based on previous studies showing active doses after central administration (Gmerek and Cowan, 1983a;Gmerek et al, 1983;Thomas and Hammond, 1995;Tohda et al, 1997). As noted, we found that 1 μg of i.c.v.…”

Section: Experimental Designmentioning

confidence: 99%

“…Although several studies have demonstrated that activation of central mu-opioid receptors produces scratching behavior in rodents (Thomas and Hammond, 1995;Tohda et al, 1997;Kuraishi et al, 2000), and that this scratching behavior can be blocked by opioid antagonists in mice and rats (Tohda et al, 1997;Yamaguchi et al, 1998;Ko et al, 1999), the dose-and time-dependent aspects of this response have not been well characterized in rats. To date, many studies have investigated the antinociceptive effects of spinal mu-opioid receptors in rodents (e.g.…”

Section: Introductionmentioning

confidence: 99%

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Characterization of scratching responses in rats following centrally administered morphine or bombesin

Lee

Naughton

Woods

et al. 2003

Behavioural Pharmacology

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The aim of this study was to characterize scratching behavior elicited by central administration of morphine or bombesin in rats, and to determine the role of opioid receptors in scratching induced by both pruritogenic agents. Central administration included intracisternal (i.c.), intrathecal (i.t.), and intracerebroventricular (i.c.v.) routes. Scratching events made with hind paws were counted by observers blinded to treatment conditions. Intracisternal morphine (0.01-0.1 μg) produced dosedependent increases in scratching; the maximum response to i.c. morphine 0.1 μg was approximately 500 scratches within a 1-hour period. Neither i.t. nor i.c.v. morphine significantly increased scratching. Bombesin (0.01 -0.32 μg) elicited robust scratching following i.c. administration. The maximum response to i.c. bombesin 0.32 μg was approximately 4000 scratches within a 1-hour period. Both i.t. and i.c.v. bombesin produced profound scratching at similar doses. Antagonist studies confirmed that mu-opioid receptors selectively mediate i.c. morphine-induced scratching. However, selective mu-, kappa-, and delta-opioid antagonists did not attenuate i.c. bombesin-induced scratching. These results demonstrate that morphine and bombesin elicit scratching through different receptor mechanisms, at different central sites, and to different degrees.

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Section: Discussionsupporting

confidence: 91%

Section: Discussionmentioning

confidence: 67%