Electrical Characteristics of Insect Mechanoreceptors

External direct coupled recordings from the neurons of the mechanosensory hairs of insects show nerve impulses and graded slow potentials in response to deformation of the hair. These slow potentials or receptor potentials are negative going, vary directly with the magnitude of the stimulus, and show no overshoot when returning to baseline. The impulses have an initial positive phase which varies in size directly with the amplitude of the receptor potential. The receptor potential is related to the generator potential for the impulse in that it must attain some critical level before impulses are produced, and the frequency of impulses varies directly with amplitude of the receptor potential. The receptor potential does not return to the baseline after each impulse. In some receptors static deformation of the hair will maintain the receptor potential. It appears likely that both the receptor potential and the variation in size of the impulses are caused by a change in conductance of the cell membrane at the receptor site, and that the receptor potential originates at a site which is not invaded by the propagated impulses.