title: Nitric oxide signals that aplysia have attempted to eat, a necessary component of memory formation after learning that food is inedible.
abstract: Inhibiting nitric oxide (NO) synthesis during learning that food is inedible in Aplysia blocks subsequent memory formation. To gain insight into the function of NO transmission during learning we tested whether blocking NO synthesis affects aspects of feeding that are expressed both in a nonlearning context and during learning. Inhibiting NO synthesis with L-NAME and blocking guanylyl cyclase with methylene blue decreased the efficacy of ad libitum feeding. D-NAME had no effect. L-NAME also decreased rejection responses frequency, but did not affect rejection amplitude. The effect of L-NAME was explained by a decreased signaling that efforts to swallow are not successful, leading to a decreased rejection rate, and a decreased ability to reposition and subsequently consume food in ad libitum feeding. Signaling that animals have made an effort to swallow is a critical component of learning that food is inedible. Stimulation of the lips with food alone did not produce memory, but stimulation combined with the NO donor SNAP did produce memory. Exogenous NO at a concentration causing memory also excited a key neuron responding to NO, the MCC. Block of the cGMP second-messenger cascade during training by methylene blue also blocked memory formation after learning. Our data indicate that memory arises from the contingency of three events during learning that food is inedible. One of the events is efforts to swallow, which are signaled by NO by cGMP.
authors.affiliation: The Leslie and Susan Gonda (Goldschmied) Multidisciplinary Brain Research Center, Bar Ilan University, Ramat Gan 52900, Israel.
authors.forename: Ayelet
authors.initials: A
authors.lastname: Katzoff
authors.forename: Tziona
authors.initials: T
authors.lastname: Ben-Gedalya
authors.forename: Itay
authors.initials: I
authors.lastname: Hurwitz
authors.forename: Nimrod
authors.initials: N
authors.lastname: Miller
authors.forename: Yehoshua Z
authors.initials: YZ
authors.lastname: Susswein
authors.forename: Abraham J
authors.initials: AJ
authors.lastname: Susswein
mesh_terms: D000818:Animals; D001048:Aplysia / Q000502:physiology*; D001362:Avoidance Learning / Q000187:drug effects / Q000502:physiology; D002755:Choice Behavior; D005247:Feeding Behavior / Q000187:drug effects / Q000502:physiology*; D007858:Learning / Q000187:drug effects / Q000502:physiology*; D008568:Memory / Q000187:drug effects / Q000502:physiology*; D008751:Methylene Blue / Q000494:pharmacology; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D009569:Nitric Oxide / Q000502:physiology*; D015398:Signal Transduction
chemical_list: D009569:Nitric Oxide; D008751:Methylene Blue; D019331:NG-Nitroarginine Methyl Ester