Mesocestoides corti (syn. M. vogae): modulation of larval motility by neuropeptides, serotonin and acetylcholine

Abstract

The effect of platyhelminth FaRPs and selected classical neurotransmitters on the motility of intact Mesocestoides corti (syn. M. vogae) tetrathyridial larvae was studied in vitro using a micromotility meter. The effects of the test substances were temperature dependent and these were examined at 4, 23, 30 and 36 °C. At 36 °C all test substances had concentration-dependent excitatory effects, with thresholds for activity of: 100 nM (GNFFRFamide), 10 μM (YIRFamide), 30 μM (GYIRFamide), 100 nM (serotonin) and 100 μM (acetylcholine). At this temperature significant elevation of motility indices (MI) was recorded within 5 min of the addition of peptide or serotonin. The effect of acetylcholine was slower in onset and appeared 15–20 min post-addition. At 30 °C larval motility diminished more rapidly than that recorded at 36 °C, following the addition of 1 mM of each test substance. At 23 °C only serotonin (1 mM) significantly increased the MI, all other test substances having no apparent effect. Larval movement was completely arrested at 4 °C. The results demonstrate for the first time excitatory effects of platyhelminth neuropeptides and acetylcholine on muscle systems in cestode larvae. The fact that the only known cestode FaRP, GNFFRFamide, was more potent than any of the turbellarian FaRPs tested, suggests structural conservation of FaRPs and FaRP receptors within the cestodes.