CB1 Cannabinoid Receptors Modulate Kinase and Phosphatase Activity During Extinction of Conditioned Fear in Mice (original) (raw)

  1. Astrid Cannich1,
  2. Carsten T. Wotjak2,
  3. Kornelia Kamprath2,
  4. Heike Hermann1,
  5. Beat Lutz1, and
  6. Giovanni Marsicano1,3
  7. Groups of 1_Molecular Genetics of Behavior and_ 2_Neuronal Plasticity/Mouse Behavior, Max Planck Institute of Psychiatry, 80804 Munich, Germany_

Abstract

Cannabinoid receptors type 1 (CB1) play a central role in both short-term and long-term extinction of auditory-cued fear memory. The molecular mechanisms underlying this function remain to be clarified. Several studies indicated extracellular signal-regulated kinases (ERKs), the phosphatidylinositol 3-kinase with its downstream effector AKT, and the phosphatase calcineurin as potential molecular substrates of extinction behavior. To test the involvement of these kinase and phosphatase activities in CB1-dependent extinction of conditioned fear behavior, conditioned CB1-deficient mice (CB1-/-) and wild-type littermates (CB1+/+) were sacrificed 30 min after recall of fear memory, and activation of ERKs, AKT, and calcineurin was examined by Western blot analysis in different brain regions. As compared with CB1+/+, the nonreinforced tone presentation 24 h after auditory-cued fear conditioning led to lower levels of phosphorylated ERKs and/or calcineurin in the basolateral amygdala complex, ventromedial prefrontal cortex, dorsal hippocampus, and ventral hippocampus of CB1-/-. In contrast, higher levels of phosphorylated p44 ERK and calcineurin were observed in the central nucleus of the amygdala of CB1-/-. Phosphorylation of AKT was more pronounced in the basolateral amygdala complex and the dorsal hippocampus of CB1-/-. We propose that the endogenous cannabinoid system modulates extinction of aversive memories, at least in part via regulation of the activity of kinases and phosphatases in a brain structure-dependent manner.

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