Figure 1

The presentation of cues associated with chocolate, and the intermittent delivery of chocolate chips, results in a reduction in the amplitude of synaptic responses in the entorhinal cortex evoked by piriform cortex stimulation. Synaptic responses were evoked every 15 sec during a baseline period, a cued period in which a cue-light and a feeding cup associated with chocolate were presented, a consumption period in which animals obtained 10 chocolate chips (1.1 g total) over a ten-min period, and a follow-up period without cues or chocolate. A: Averaged evoked synaptic field potentials from a representative animal are shown for each testing period following an injection of saline. The averaged baseline trace is superimposed as dotted lines for comparison. B: Mean amplitudes of field excitatory postsynaptic potentials (fEPSPs) averaged in 2.5 min-duration bins and are shown for tests conducted following injection of saline (B₁, n = 14), the D₁ receptor blocker SCH23990 (B₂), the D₂ receptor blocker eticlopride (B₃), or the muscarinic receptor blocker scopolamine (B₄). Data for each animal have been normalized to the mean amplitude of responses during the baseline period, and error bars indicate ± one standard error of the mean. Mean results are compared across testing conditions in B₅ (*p < .05 vs. baseline). C: The mean proportion of time that animals spent moving during each phase of testing reflects increased mobility during anticipation and consumption of chocolate following saline injections, increased mobility during consumption of chocolate following injection of either D₁ or D₂ receptor antagonists, and increased mobility following injection of scopolamine.