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. Author manuscript; available in PMC: 2012 Mar 1.
Published in final edited form as: Behav Brain Res. 2010 Oct 23;217(2):477–480. doi: 10.1016/j.bbr.2010.10.022

Figure 1. Comparison of a thermal and a mechanical operant testing system.

Figure 1

Photograph of a rat performing a thermal (A) and mechanical (B) facial operant test. In each test, the rats’ cheeks must contact the thermode or stimulus wires in order to reach the reward bottle containing sweetened condensed milk. Comparison of the Lick/Face contact pain ratio for thermal (C) and mechanical (D) stimuli demonstrated that there was a significant decrease in the Lick/Face ratio when the stimulus thermode was set at 48°C (N=134) as compared to 37°C (N=82; ***p<0.0001). There was a similar decrease in this ratio when comparing NiTi wires with a diameter of 0.010” (N=10) and 0.007” (N=10; ***p<0.005).