Proprioceptive indentation of the campaniform sensilla of cockroach legs

1. Individual proprioceptive campaniform sensilla of tibial Group 6 in the cockroach Blaberus discoidalis were stimulated by combinations of proprioceptive and punctate stimuli. 2. Punctate stimulation during a proprioceptive discharge increased the response rather than decreasing it, indicating that proprioceptive stimuli indent, rather than bulge, the cap of the sensillum. 3. The magnitude of the indentation associated with a strong proprioceptive discharge was estimated from compliance and sensitivity measurements to be in the range 10 to 50 nanometers. 4. The excitatory strain of the tibial cuticle appears to be compression perpendicular to the long axis of the cap of the sensillum. We suggest that the elaborate structure of the cap cuticle serves to amplify the tibial cuticular strain to squeeze the terminal of the dendritic sensory process.