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Title: Nimodipine is more effective than nifedipine in attenuating morphine tolerance on chronic co-administration in the rat tail-flick test
Authors: Ray, Subrata Basu
Mishra, Pravash
Verma, Dilip
Gupta, Ankur
Wadhwa, Shashi
Keywords: Ca<sup>2+</sup> channel blockers
Morphine tolerance
Neuronal plasticity
Issue Date: Apr-2008
Publisher: CSIR
Abstract: Opioids, when co-administered with L-type calcium channel blockers (L-CCBs) show morphine like higher antinociceptive effect. This antinociceptive effect has been further investigated using a different experimental paradigm. The effect of two different L-CCBs (nifedipine and nimodipine) on morphine-induced antinociception was studied by the tail-flick test (40 min after morphine administration) in adult Wistar rats. A fixed-dose of nimodipine or nifedipine (2 mg/kg, once daily) was combined with a fixed dose of morphine (10 mg/kg, twice daily) for 10 days. Co-administration of L-CCBs significantly increased the antinociceptive effect of morphine, even 12 hr after administration. Also, nimodipine was more effective than nifedipine. Nimodipine was further studied using a higher and escalating doses of morphine (20 – 30 mg/kg twice daily for 14 days). Nimodipine increased the antinociceptive effect of morphine in the latter part of the study (days nine to fourteen) though significant difference was observed on 11<sup>th</sup> evening and 12<sup>th</sup> morning. No obvious adverse effects were observed in the present study. The results show for the first time that nimodipine is more effective than nifedipine and that these L-CCBs continue to be effective, even 12 hr after administration in the tail-flick test. <u></u>
Description: 219-228
ISSN: 0019-5189
Appears in Collections:IJEB Vol.46(04) [April 2008]

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