B. Tamba *, Irina M. Jaba **, Liliana Tartău **, V. Cojocaru **, Dunărea Georgeta Ionescu ***, O. C. Mungiu ****
Abstract
Manganese (Mn) is known to block voltage-activated lcium currents and through that to block depolarizationca of excitable neuronal membranes, though the mechanisms underlying this process is not yet totally clear. In this con text, the study investigates a possible modulator effect in nociception for systemically administered Mn. Groups of 7 mice were treated with manganese chloride 3 mg/kg body weight, administered intraperitoneal. Different tests were utilized to evaluate the antinociceptive effect or the influence on behavior of the substances tested: thermal nociception (hot plate test, tail flick test), chemical noci ception (writhing test) and spontaneous behavior (activity cage assay). Values for response latencies obtained for hot-plate and tail-flick tests prove that Mn administered systemically produces an analgesic effect under thermal nociceptive stimulation. Although limited in time, this ac tion is especially strong shortly after Mn treatment. Pain inhibition is even more significant in conditions of chemical nociceptive stimulation, in a model of visceral pain. The mechanism through which Mn exerts its analgesic effect is still unclear, although it is possible to be explained by a blockade of NMDA receptors, as shown by recent indi rect research, related to the influence of Mn superoxide dismutase enzyme on pain mediation and hyperalgesia.