Figure 2.

Sensory nerves in naive snails show similar responses to sucrose and AA application to the lips. (A) Simultaneous recordings from median lip nerve (mln), superior lip nerve (sln), and tentacle nerve (tn) showing responses of the three nerves to sucrose (0.02 M, 30 sec) applied to the lips. Note that the lip and tentacle nerves showed a considerable level of spontaneous activity that varied to some extent between individual preparations, including both tonic firing and spontaneous bursts of activity. The level of spontaneous activity did not influence the overall responses of the nerves to chemical stimulation of the lips. All nerves to the lips were cut to remove efferent influences from the CNS. (B) Equivalent record from another preparation showing responses of the same three nerves to AA (0.54 mM, 30 sec) applied to the lips. It should be noted that the two unidentified larger units that fire at an almost constant frequency throughout the record contributed only a small proportion to the overall nerve activity and that the main change in activity occurred in the small to medium sized units. (C,D) Average time course of changes in nerve firing rates in median lip nerve, superior lip nerve and tentacle nerve in response to sucrose (C, n = 7 preparations; error bars not shown for clarity) and AA (D, n = 7 preparations; error bars not shown for clarity) application.