Peptide actions on oviduct contractions in the large pine weevil, Hylobius abietis

  The peptides proctolin, crustacean cardioactive peptide (CCAP) and FMRFamide, which are known to modulate insect muscle contractions, were assayed for their action on oviduct contractions in Hylobius abietis . A video microscopy technique and computer‐based method of data acquisition and analysis were used to investigate the effects of theses peptides on spontaneous contractions of continuously perfused oviducts. All three peptides tested stimulate spontaneous contraction activity of the pine weevil oviduct, increasing the frequency and amplitude of phasic contractions in a dose‐dependent manner. Proctolin is more potent as a stimulator than CCAP. For proctolin a threshold response of oviduct muscles is at concentration of peptide 10 −11 –10 −10 mol/L and for CCAP at concentration range 10 −10 –10 −9 mol/L. FMRFamide exerts a weak stimulatory effect on the oviduct, and at higher concentrations of the peptide (above 10 −8 mol/L). The peptides exert different responses on oviduct contractions and they may play a role as functional regulators in such processes as egg movement and oviposition.