Drug Res (Stuttg) 2014; 64(3): 113-117
DOI: 10.1055/s-0033-1355364
Original Article
© Georg Thieme Verlag KG Stuttgart · New York

Effect of Cyanocobalamin (vitamin B12) in the Induction and Expression of Morphine Tolerance and Dependence in Mice

S. Ghazanfari
1   Department of Pharmacodynamy and Toxicology, School of Pharmacy, Mashhad University of Medical Sciences, Mashhad, IR. Iran
,
M. Imenshahidi
1   Department of Pharmacodynamy and Toxicology, School of Pharmacy, Mashhad University of Medical Sciences, Mashhad, IR. Iran
,
L. Etemad
1   Department of Pharmacodynamy and Toxicology, School of Pharmacy, Mashhad University of Medical Sciences, Mashhad, IR. Iran
,
M. Moshiri
1   Department of Pharmacodynamy and Toxicology, School of Pharmacy, Mashhad University of Medical Sciences, Mashhad, IR. Iran
,
H. Hosseinzadeh
1   Department of Pharmacodynamy and Toxicology, School of Pharmacy, Mashhad University of Medical Sciences, Mashhad, IR. Iran
› Author Affiliations
Further Information

Publication History

received 29 May 2013

accepted 25 July 2013

Publication Date:
08 October 2013 (online)

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Abstract

The antinociceptive effect of cyanocobalamin (Vit B12) has been reported in animal models and human studies. Our previous study showed the effect of Vit B12 on morphine tolerance. The dependence and tolerance were induced in male mice using subcutaneous morphine injections, 3 times a day (50, 50 and 75 mg/kg/day) for 3 days. Mice also received Vit B12 (100, 250 and 500 µg/kg), clonidine, memantine and saline intraperitoneally before morphine administration. On fourth day mice received only 7 mg /kg morphine just before tail-flick test. To determine the expression of morphine dependence and tolerance, all compounds were injected once intraperitoneally on the day of experiment. The tolerance was evaluated by the tail-flick test. The effect of Vit B12 and other agents on dependence were evaluated by counting the number of jumps (induced by naloxone 5 mg/kg). Co-administration of Vit B12 (100–500 µg/kg) and morphine in 3 days reduced the development of tolerance to morphine analgesic effect (8.2±0.5 and 7.83±0.5 s. vs. normal saline, 3.57±0.3 s). Repeated administration of Vit B12, also, diminished the reduced naloxane withdrawal signs of naloxone withdrawal test (100–500 µg/kg: 5±1.9 and 1.2±0.8 jumps vs. normal saline 72.6±12.2). However, Vit B12 had no effect on the expression of morphine tolerance and physical dependence. It is concluded that co-administration of Vit B12 and morphine could reduce tolerance to analgesic effect of morphine chronic administration and also reduce its withdrawal symptoms.