An in vitro analog of learning that food is inedible in Aplysia: decreased responses to a transmitter signaling food after pairing with transmitters signaling failed swallowing

Effects of pairing histamine or NO with a cholinomimetic versus effects of histamine or NO alone. (A) Number of fictive feeding bouts during the first (blue) and last (red) exposure to CCh. Between the first and last exposures to CCh, the cerebral ganglion was exposed to either NO or HA paired with CCh, to NO or HA alone (in ASW), or to CCh alone. Significant changes are marked by an asterisk. (B) Percent change in the number of fictive feeding bouts between the first and last two exposures to CCh (for paired and unpaired exposures to NO and histamine) and to CCh alone. Standard errors are shown in both A and B.