BEHAVIOR INDUCES EXPRESSION OF THE PLASTICITY-RELATED IMMEDIATE-EARLY GENE ARC IN EXCITATORY AND INHIBITORY CAMKII-POSITIVE NEURONS

A. Vazdarjanova¹*; V. Ramirez-Amaya¹; N. Insel¹;
P.F. Worley²; J.F. Guzowski³; C.A. Barnes¹

1. NSMA, Univ Arizona, Tucson, AZ, USA
2. Neurosci & Neurol, Johns Hopkins Univ, Baltimore, MD, USA
3. Neurosci, Univ New Mexico, Albuquerque, NM, USA

The activity-regulated cytoskeletal associated protein (Arc or Arg 3.1) is a key protein implicated in synaptic plasticity and memory consolidation in hippocampus and neocortex. Initial characterization of the cell types expressing Arc in the hippocampal CA regions and in parietal cortex after exploration of a novel environment revealed that Arc is expressed only in CAMKII+ neurons, but not in GAD65/67+ neurons. These findings suggested that after behavioral exploration Arc may be expressed solely in excitatory neurons. Consistent with this hypothesis here we report that Arc is expressed in CAMKII+, but not in GAD65/67+ neurons in the dentate gyrus of rats that have explored a novel environment. However, we further report that in the striatum of the same animals Arc is induced in a large percent of the GAD65/67+ neurons. Double catFISH (a sensitive fluorescence in situ hybridization method) for Arc and CAMKII revealed that in the striatum all Arc+ neurons are also CAMKII+. Combined with our previous findings these results suggest that Arc is induced in the principal neurons (excitatory or inhibitory) of brain areas activated by behavioral exploration, provided these neurons also express CAMKII. These findings lend further support for the hypothesis that Arc is integral to synaptic modification that accompanies learning.

Support Contributed By: MH64357, MH60123, AG09219 & HFSP LT00112-2002-C