The false-positive responses of analgesic drugs to the intradermal serotonin- and compound 48/80-induced scratches as an animal model of itch.
Intradermal injection of pruritogens such as serotonin, histamine and compound 48/80 into the skin and then, the evaluation of the scratching behavior is the commonly used animal model to advance pruritic research and drug development. However, predictive validity of this model is poorly documented. There is a close interaction between itch and pain sensations with regard to mediation through an anatomically and functionally identical neuronal pathway. One approach is whether the existing animal model of itch differentiates itch or pain to show efficacy of clinically effective analgesic drugs as a back translation. In this study, we explored the effects of different group of analgesic drugs on serotonin and compound 48/80-induced scratching behavior in Balb-C mice. Serotonin (25 μg) and compound 48/80 (100 μg) was injected intradermally in a volume of 50 μl into the rostral part of skin on the back of male mice and scratches were counted for a 30-min observation period. Morphine (1, 3, 10 mg/kg), tramadol (20, 40, 80 mg/kg), cannabinoid agonist CP 55,940 (0.1, 0.3, 1 mg/kg), paracetamol (100, 200, 300 mg/kg) and diclofenac (50, 100, 200 mg/kg) were given intraperitoneally 30 min prior to pruritogen injection. The analgesic drugs dose dependently blocked serotonin and compound 48/80-induced straching behavior with exerting complete inhibition at certain doses. Our data suggests that intradermal pruritogen-induced scratching models may not discriminate pain and itch sensations and give false positive results when standard analgesic drugs are used.
Department of Pharmacology, Faculty of Medicine, Ondokuz Mayıs University, Samsun, Turkey. fatihilkaya@gmail.com.
Fatih
F
Ilkaya
Department of Pharmacology, Gulhane Military Academy of Medicine, Etlik, Ankara, Turkey.
Ozgur
O
Yesilyurt
Department of Pharmacology, Gulhane Military Academy of Medicine, Etlik, Ankara, Turkey.
Melik
M
Seyrek
Department of Medical Pharmacology, Faculty of Medicine, Trakya University, Edirne, Turkey.
Ozgur
O
Gunduz
Department of Laboratory Animal Health Center for Research and Development, Gülhane Military Medical Academy, Ankara, Turkey.
Tayfun
T
Ide
Department of Dermatology, Gülhane School of Medicine, Gülhane Military Medical Academy, Ankara, Turkey.
Ahmet
A
Akar
Department of Medical Pharmacology, Faculty of Medicine, Trakya University, Edirne, Turkey.
Ahmet
A
Ulugol
Department of Pharmacology, Faculty of Medicine, Ondokuz Mayıs University, Samsun, Turkey.
Hasan
H
Guzel
Department of Pharmacology, Gulhane Military Academy of Medicine, Etlik, Ankara, Turkey.
Ahmet
A
Dogrul
Department of Physiology, Faculty of Medicine, Ondokuz Mayıs University, Samsun, Turkey.
Durmus
D
Ucar
Department of Pharmacology, Faculty of Medicine, Ondokuz Mayıs University, Samsun, Turkey.
Caner
C
Gunaydin
D000700:Analgesics / Q000627:therapeutic use*; D000818:Animals; D004195:Disease Models, Animal; D004305:Dose-Response Relationship, Drug; D004333:Drug Administration Routes; D004359:Drug Therapy, Combination; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D011537:Pruritus / Q000139:chemically induced* / Q000188:drug therapy*; D012701:Serotonin / Q000633:toxicity*; D013997:Time Factors; D003189:p-Methoxy-N-methylphenethylamine / Q000633:toxicity*
D000700:Analgesics; D012701:Serotonin; D003189:p-Methoxy-N-methylphenethylamine