Fig. 8. Blocking impulses generated in receptor endings with anaesthetic abolishes the spontaneous activity of cement gland mechanosensory neurons. (A) Diagram of the preparation. An electrode on the trigeminal ganglion recorded multi-unit activity. A microperfusion nozzle was positioned so the microperfusate flowed over the distal end of the mandibular nerve and the cement gland. The flow of the bath perfusion ensured the microperfusate was washed away and did not contact the trigeminal ganglion. Microperfusion of anaesthetic (0.1% MS-222) onto the distal mandibular nerve as it innervates the cement gland produced the following effects. (B) MS-222 abolished the trigeminal response (trig) to pulling the cement gland mucus. Tungsten wire mounted in a glass capillary is attached by a lever to a loudspeaker cone, the input to which is shown (pull). The tungsten wire pulls on the cement gland mucus when the line (pull) moves down. Horizontal scale bar, 2.5 s (C) MS-222 abolished spontaneous activity. Horizontal scale bar, 60 s. (D) MS-222 did not abolish the antidromic spikes produced by a 300 µs stimulus pulse to the hindbrain (at arrows). Subthreshold stimulation (thin line) is shown together with a response (thick line). After washing off MS-222 by switching microperfusion to saline, spontaneous activity returned. Horizontal scale bar, 14 ms.