Electropharyngeograms and stylet activity of second stage juveniles of Globodera rostochiensis

Analysis of the contraction and relaxation of pharyngeal musculature derive s from measurements of electrical currents, termed electropharyngeograms (E PG). EPG of stylet protractor muscle activity of second stage juveniles (J2 ) of Globodera rostochiensis, in response to 0.1. 1.0 and 10 mg ml(-1) conc entrations of the neurotransmitter serotonin. have now been obtained and co rrelated with stylet protrusion and retraction using video analysis. The an tagonist, gramine (10 mg ml(-1)), incorporated with 10 mg ml(-1) serotonin, almost completely eliminated stylet thrusting by J2. Stylet movement can b e determined accurately over extended periods with EPG and this approach ha s potential for investigating factors involved in activation and perturbati on of stylet protrusion.