Fig. 8.

Effects of trochanteral campaniform sensilla on activity in the trochanteral depressor muscle. A: recording of effects of repetitive indentation of the cuticular caps of Group 4 campaniform sensilla on tonic activities of the slow trochanteral depressor motoneuron (Ds). Each mechanical stimulus produced a transient increase in the depressor firing frequency. B: histogram of tests from 3 preparations shows consistent depressor excitation at short latency from Group 4 stimulation. C: effects of stimulation of the cap of a Group 3 sensillum on depressor firing. Depressor firing was completely inhibited by sensillum activation. D: histogram of tests (from the same 3 preparations) shows consistent inhibition following indentation of Group 3 sensilla. E and F: effects of forces applied in the direction of levation in a preparation with only Group 3 and 4 sensilla intact. In preparations showing tonic postural activity, forces applied toward levation produced inhibition of depressor firing (E, top; F, top). Large active muscle contractions could be evoked after stimulation of the abdomen or cercus. Forces applied toward levation then produced excitation of the depressor (E, middle; F, middle). Both the inhibitory and excitatory effects were eliminated by ablation of the trochanteral campaniform sensilla (E, bottom; F, bottom).