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. 2006 Apr 12;26(15):4139–4146. doi: 10.1523/JNEUROSCI.0489-06.2006

Figure 2.

Figure 2.

Identification of two separate CS processing pathways in naive animals. A, Concentration dependence of CS effects on feeding behavior in naive animals indicates the existence of two independent CS processing pathways with different activation thresholds. At 0.004%, the CS is a behaviorally “neutral” stimulus that does not significantly alter the spontaneous feeding activity. However, 0.002% CS results in a significant increase in feeding activity, and 0.02% CS significantly inhibits feeding activity. Statistical analysis revealed a strong negative correlation between the CS concentration and its effect on feeding (Spearman’s rank correlation: ρ=−0.59; p < 0.01). *p < 0.05. B, C, Opposing effects of CS application to the lips and esophagus on fictive feeding activity in semi-intact preparations. Bi, Schematic diagram of whole CNS semi-intact preparation. The semi-intact preparation consisted of the lip structures, the esophagus, and the whole CNS, including the cerebral ganglia (cg) and buccal ganglia (bg). A custom-built superfusion system enabled the separate stimulation of the lips and the inside of the esophagus with the CS. The CS effects on fictive feeding activity were monitored by recording electrical activity in buccal feeding motoneurons including the B3 using standard intracellular recording techniques. cbc, Cerebral buccal connectives. Bii, The 0.02% CS application to the lips for 2 min significantly suppressed fictive feeding activity (CS) compared with the 2 min period before stimulus application (baseline). Additional tests with lower CS concentrations (0.004 and 0.002%) had no significant effect on fictive feeding activity (paired t tests, p > 0.05; n=12). Biii, CS application to the esophagus significantly increased fictive feeding over baseline activity at all concentrations tested. *p < 0.05; **p < 0.01. Ci, Sample record from B3 motoneuron showing suppression of fictive feeding as indicated by reduction of B3 activity from four bursts before 0.02% CS application to the lips to a single burst during CS application. Cii, Sample record from B3 motoneuron showing stimulation of fictive feeding as indicated by the increase in B3 activity from three bursts before 0.002% CS application to the esophagus to seven bursts during CS application.