Itch-Scratch Responses Induced by Opioids
through Central Mu Opioid Receptors in Mice
by
Kuraishi Y, Yamaguchi T, Miyamoto T
Department of Applied Pharmacology,
Faculty of Pharmaceutical Sciences,
Toyama Medical and Pharmaceutical University,
Toyama, Japan.
J Biomed Sci 2000 May;7(3):248-252

ABSTRACT

We examined scratch-inducing effects of intracisternal, intrathecal and intradermal injections of morphine and some opioid agonists in mice. Intracisternal injection of morphine (3 nmol/animal) and the mu-receptor agonist [D-Ala(2), N-Me-Phe(4), Gly(5)-ol]enkephalin (DAMGO; 0.2 nmol/animal) elicited scratching of the face, with little effect on scratching of the trunk. Intracisternal injection of the delta-receptor agonist [D-Pen(2,5)]enkephalin (DPDPE) and the kappa-receptor agonist U50488 were without effects. Intrathecal injection of morphine (0.1-3 nmol/animal) produced a dose-dependent increase in body scratching, with little effects on face scratching. Face scratching induced by intrathecal morphine (3 nmol/animal) was almost abolished by subcutaneous pretreatment with naloxone (1 mg/kg). Intradermal injections of morphine (3-100 nmol/site), DAMGO (1-100 nmol/site), DPDPE (10 and 100 nmol/site) and U50488 (10-100 nmol/site) did not elicit scratching of the site of injection. Intradermal injection of histamine (100 nmol/site) induced the scratching in ICR, but not ddY, mice and serotonin (30 and 50 nmol/site) elicited the scratching in either strain of mice. The results suggest that opioids induce scratching, and probably itching, through central mu-opioid receptors in the mouse

Itch
Pain
LAAM
Heroin
Arousal
Morphine
Tramadol
Histamine
Nociceptin
Methadone
Endomorphins
P-glycoprotein
Novelty and pain
Methylnaltrexone
Alvimopan for OBD
Opioid bowel dysfunction
Methylnaltrexone for OBD
Opioids, mood and cognition
Topical opioid antagonist for itching

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