Fig. 4. Multiple-unit activity in trigeminal sensory neurons innervating the cement gland is increased by attaching a weight to the mucus strand. (A) Diagram of the head end of the inverted tadpole preparation. The weight attached to the cement gland mucus simulates attachment. Multi-unit activity is recorded by a suction electrode on the trigeminal ganglion. (B) Examples of a 30 s duration multi-unit recording showing spontaneous spike activity in the unattached state and increased activity when the weight is attached. (C) Combined results from 7 animals showing a sustained increase in trigeminal activity over a 60 min period of weight attachment and a return to control levels after the weight is removed. Activity is measured as the number of spikes in each 30 s period and is normalised relative to that at 25 min for each recording. Values are means + S.D.