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Updated: Aug 15, 2026
Assessment of Morphine-induced Hyperalgesia and Analgesic Tolerance in Mice Using Thermal and Mechanical Nociceptive Modalities
Published on: July 29, 2014
Enhanced analgesic effect of morphine-nimodipine combination after intraspinal administration as compared to systemic
Dilip Verma1, Subrata Basu Ray, Ishan Patro
1Department of Anatomy, All India Institute of Medical Sciences, New Delhi 110 029, India.
Abstract:
Calcium plays an important role in the pathophysiology of pain. A number of studies have investigated the effect of L-type calcium channel blockers on the analgesic response of morphine. However, the results are conflicting. In the present study, the antinociceptive effect of morphine (2.5 microg) and nimodipine (1 microg) co-administered intraspinally in mice was observed using the tail flick test. It was compared to the analgesic effect of these drugs (morphine - 250 microg subcutaneously; nimodipine - 100 microg intraperitoneally) after systemic administration. Nimodipine is highly lipophilic and readily crosses the blood brain barrier. Addition of nimodipine to morphine potentiated the analgesic response of the latter when administered through the intraspinal route but not when administered through systemic route. It may be due to direct inhibitory effect of morphine and nimodipine on neurons of superficial laminae of the spinal cord after binding to mu -opioid receptors and L-type calcium channels respectively.
