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The Journal of Neuroscience, May 5, 2004, 24(18):4460-4468; doi:10.1523/JNEUROSCI.0669-04.2004

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Behavioral/Systems/Cognitive
Learning at Different Satiation Levels Reveals Parallel Functions for the cAMP–Protein Kinase A Cascade in Formation of Long-Term Memory

Anke Friedrich, Ulf Thomas, and Uli Müller

Institut für Biologie-Neurobiologie, Freie Universität Berlin, 14195 Berlin, Germany

Learning and memory formation in intact animals is generally studied under defined parameters, including the control of feeding. We used associative olfactory conditioning of the proboscis extension response in honeybees to address effects of feeding status on processes of learning and memory formation. Comparing groups of animals with different but defined feeding status at the time of conditioning reveals new and characteristic features in memory formation. In animals fed 18 hr earlier, three-trial conditioning induces a stable memory that consists of different phases: a mid-term memory (MTM), translation-dependent early long-term memory (eLTM; 1–2 d), and a transcription-dependent late LTM (lLTM; 3 d). Additional feeding of a small amount of sucrose 4 hr before conditioning leads to a loss of all of these memory phases. Interestingly, the basal activity of the cAMP-dependent protein kinase A (PKA), a key player in LTM formation, differs in animals with different satiation levels. Pharmacological rescue of the low basal PKA activity in animals fed 4 hr before conditioning points to a specific function of cAMP–PKA cascade in mediating satiation-dependent memory formation. An increase in PKA activity during conditioning rescues only transcription-dependent lLTM; acquisition, MTM, and eLTM are still impaired. Thus, during conditioning, the cAMP–PKA cascade mediates the induction of the transcription-dependent lLTM, depending on the satiation level. This result provides the first evidence for a central and distinct function of the cAMP–PKA cascade connecting satiation level with learning.

Key words: learning; memory; protein kinase; satiety; response; cAMP

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Received Feb 24, 2004; revised March 30, 2004; accepted March 31, 2004.

This article has been cited by other articles:

				G. A. Wright, J. A. Mustard, S. M. Kottcamp, and B. H. Smith Olfactory memory formation and the influence of reward pathway during appetitive learning by honey bees J. Exp. Biol., November 15, 2007; 210(22): 4024 - 4033. [Abstract] [Full Text] [PDF]

				J.-C. Sandoz and M.-H. Pham-Delegue Spontaneous Recovery After Extinction of the Conditioned Proboscis Extension Response in the Honeybee Learn. Mem., September 1, 2004; 11(5): 586 - 597. [Abstract] [Full Text] [PDF]

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