title: Effects of nifedipine on behavioral and biochemical parameters in rats after multiple morphine administration.
abstract: Numerous studies indicate that opioid tolerance involves a disruption in Ca2+ homeostasis. In vivo studies have indicated the involvement of dihydropyridine-sensitive (L-type) voltage-gated channels in morphine abuse. In this study, the effect of multiple administration of the dihydropyridine calcium channel blocker nifedipine (5 mg/kg/twice daily), given in combination with morphine, on the signs of morphine withdrawal and some biochemical parameters were assessed. Multiple morphine administration in increasing doses (from 5 to 40 mg/kg for 7 days) and consequent withdrawal after 18 h, induced writhing, squealing, diarrhea, teeth chattering, eyelid ptosis and wet-dog type shaking. Coadministration of nifedipine prevented the squealing, diarrhea and teeth chattering. On a biochemical level, the activity of brain nitric oxide synthase (NOS) and the quantity of cytochrome P450 in rat brain and liver were measured. Nifedipine treatment decreased the brain nNOS activity, induced by multiple administration of morphine. The quantity of liver cytochrome P450, after multiple coadministration of morphine and nifedipine, was also increased. The quantity of brain cytochrome P450 was not significantly changed by morphine and nifedipine alone or in combination. The results of our study suggest that nifedipine influences the effects of morphine both at a pharmacokinetic and a pharmacodynamic level.
authors.affiliation: Department of Pharmacology and Toxicology, Faculty of Pharmacy, Medical University, Sofia, Bulgaria.
authors.forename: V
authors.initials: V
authors.lastname: Vitcheva
authors.forename: M
authors.initials: M
authors.lastname: Mitcheva
mesh_terms: D000701:Analgesics, Opioid / Q000008:administration & dosage / Q000009:adverse effects*; D000818:Animals; D001522:Behavior, Animal / Q000187:drug effects; D001921:Brain / Q000201:enzymology; D002121:Calcium Channel Blockers / Q000494:pharmacology*; D003577:Cytochrome P-450 Enzyme System / Q000032:analysis / Q000378:metabolism*; D004338:Drug Combinations; D004347:Drug Interactions; D008297:Male; D008861:Microsomes / Q000201:enzymology; D008862:Microsomes, Liver / Q000201:enzymology; D009020:Morphine / Q000008:administration & dosage / Q000009:adverse effects*; D009021:Morphine Dependence / Q000209:etiology* / Q000503:physiopathology / Q000517:prevention & control; D009419:Nerve Tissue Proteins / Q000032:analysis / Q000378:metabolism*; D009543:Nifedipine / Q000494:pharmacology*; D019001:Nitric Oxide Synthase / Q000032:analysis / Q000378:metabolism*; D052248:Nitric Oxide Synthase Type I; D051381:Rats; D017208:Rats, Wistar; D013375:Substance Withdrawal Syndrome / Q000378:metabolism* / Q000517:prevention & control
chemical_list: D000701:Analgesics, Opioid; D002121:Calcium Channel Blockers; D004338:Drug Combinations; D009419:Nerve Tissue Proteins; D009020:Morphine; D003577:Cytochrome P-450 Enzyme System; D019001:Nitric Oxide Synthase; D052248:Nitric Oxide Synthase Type I; C496322:Nos1 protein, rat; D009543:Nifedipine