Antinociceptive effect of MAS MT in rats.

摘要

MAS MT is a myotropic decapeptide isolated from Manduca sexta. This peptide exerts stimulatory effect on the heart-beat frequency of insects. The present study was conducted to determine a probable antinociceptive effect in rats of a native synthetic decapeptide, MAS MT-I, and its 2 analogues, heptapeptides MAS MT-II and MAS MT-III. All these peptides were applied directly into the lateral brain ventricle (icv) at 3 doses: 10, 25 and 50 nmol. The analgesic (antinociceptive) effect was evaluated by a tail immersion test. It was found that 25 and 50 nmol of MAS MT-I induced significant antinociceptive effect, while MAS MT-II and MAS MT-III exerted a less antinociceptive effect in comparison with native MAS MT-I. Prior icv administration of naloxone, an opioid antagonist, weakly blocked the MAS MT-I effect. It is concluded that the antinociceptive effect of MAS MT-I in rats is not mediated by the central opioid system.