title: Critical time-window for NO-cGMP-dependent long-term memory formation after one-trial appetitive conditioning.
abstract: The nitric oxide (NO)-cGMP signaling pathway is implicated in an increasing number of experimental models of plasticity. Here, in a behavioral analysis using one-trial appetitive associative conditioning, we show that there is an obligatory requirement for this pathway in the formation of long-term memory (LTM). Moreover, we demonstrate that this requirement lasts for a critical period of approximately 5 hr after training. Specifically, we trained intact specimens of the snail Lymnaea stagnalis in a single conditioning trial using a conditioned stimulus, amyl-acetate, paired with a salient unconditioned stimulus, sucrose, for feeding. Long-term associative memory induced by a single associative trial was demonstrated at 24 hr and shown to last at least 14 d after training. Tests for LTM and its dependence on NO were performed routinely 24 hr after training. The critical period when NO was needed for memory formation was established by transiently depleting it from the animals at a series of time points after training by the injection of the NO-scavenger 2-phenyl-4,4,5,5-tetramethyl-imidazoline-1-oxyl 3-oxide (PTIO). By blocking the activity of NO synthase and soluble guanylyl cyclase enzymes after training, we provided further evidence that LTM formation depends on an intact NO-cGMP pathway. An electrophysiological correlate of LTM was also blocked by PTIO, showing that the dependence of LTM on NO is amenable to analysis at the cellular level in vitro. This represents the first demonstration that associative memory formation after single-trial appetitive classical conditioning is dependent on an intact NO-cGMP signaling pathway.
authors.affiliation: Sussex Centre for Neuroscience, School of Biological Sciences, University of Sussex, Falmer, Brighton, United Kingdom, BN1 9QG. I.Kemenes@sussex.ac.uk
authors.forename: Ildikó
authors.initials: I
authors.lastname: Kemenes
authors.forename: György
authors.initials: G
authors.lastname: Kemenes
authors.forename: Richard J
authors.initials: RJ
authors.lastname: Andrew
authors.forename: Paul R
authors.initials: PR
authors.lastname: Benjamin
authors.forename: Michael
authors.initials: M
authors.lastname: O'Shea
mesh_terms: D000818:Animals; D001070:Appetitive Behavior / Q000187:drug effects / Q000502:physiology*; D003214:Conditioning, Classical / Q000187:drug effects / Q000502:physiology; D006152:Cyclic GMP / Q000378:metabolism*; D003497:Cyclic N-Oxides / Q000008:administration & dosage; D004334:Drug Administration Schedule; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005247:Feeding Behavior / Q000187:drug effects / Q000502:physiology; D016166:Free Radical Scavengers / Q000008:administration & dosage; D006162:Guanylate Cyclase; D007093:Imidazoles / Q000008:administration & dosage; D008195:Lymnaea; D008568:Memory / Q000187:drug effects / Q000502:physiology*; D009473:Neuronal Plasticity / Q000187:drug effects / Q000502:physiology; D009569:Nitric Oxide / Q000378:metabolism*; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors; D000439:Pentanols / Q000494:pharmacology; D018160:Receptors, Cytoplasmic and Nuclear / Q000037:antagonists & inhibitors; D012153:Retention, Psychology / Q000187:drug effects / Q000502:physiology; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology; D000071756:Soluble Guanylyl Cyclase; D013395:Sucrose / Q000494:pharmacology; D013997:Time Factors
chemical_list: D003497:Cyclic N-Oxides; D004791:Enzyme Inhibitors; D016166:Free Radical Scavengers; D007093:Imidazoles; D000439:Pentanols; D018160:Receptors, Cytoplasmic and Nuclear; C079391:2-phenyl-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide; D009569:Nitric Oxide; D013395:Sucrose; C005716:amyl acetate; D019001:Nitric Oxide Synthase; D006162:Guanylate Cyclase; D000071756:Soluble Guanylyl Cyclase; D006152:Cyclic GMP