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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.
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