Noradrenergic Action in Prefrontal Cortex in the Late Stage of Memory Consolidation

  1. Sophie Tronel1,
  2. Matthijs G.P. Feenstra2, and
  3. Susan J. Sara1,3
  1. 1Neuromodulation and Memory Processes, Unité Mixte de Recherche 7102, Centre National de la Recherche Scientifique, Université Pierre et Marie Curie, Paris 75005, France 2Netherlands Institute for Brain Research, 1105 AZ Amsterdam, The Netherlands

Abstract

These experiments investigated the role of the noradrenergic system in the late stage of memory consolidation and in particular its action at β receptors in the prelimbic region (PL) of the prefrontal cortex in the hours after training. Rats were trained in a rapidly acquired, appetitively motivated foraging task based on olfactory discrimination. They were injected with a β adrenergic receptor antagonist into the PL 5 min or 2 h after training and tested 48 h later. Rats injected at 2 h showed amnesia, whereas those injected at 5 min had good retention, equivalent to saline-injected controls. Monitoring extracellular noradrenaline efflux in PL by in vivo microdialysis during the first hours after training revealed a significant increase shortly after training, with a rapid return to baseline, and then another increase around the 2-h posttraining time window. Pseudo-trained rats showed a smaller early efflux and did not show the second wave of efflux at 2 h. These results confirm earlier pharmacological and immunohistochemical studies suggesting a delayed role of noradrenaline in a late phase of long-term memory consolidation and the engagement of the PL during these consolidation processes.

Footnotes

  • Article published online ahead of print. Article and publication date are at http://www.learnmem.org/cgi/doi/10.1101/lm.74504.

    • Accepted May 6, 2004.
    • Received January 22, 2004.
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