Abstract
Environmental enrichment (EE) has been shown to produce beneficial
effects in addiction disorders; however, due to its configurational
complexity, the underlying mechanisms are not yet fully elucidated.
Recent evidence suggests that EE, acting as a metaplastic agent, may
affect glutamatergic mechanisms underlying appetitive memory and, in
turn, modulate reward-seeking behaviors: here, we have investigated such
possibility following a brief EE exposure.
Adult male Sprague-Dawley rats were exposed to EE for 22h and the
expression of critical elements of the glutamate synapse was measured 2h
after the end of EE in the medial prefrontal cortex (mPFC), nucleus
accumbens (NAc), and hippocampus (Hipp) brain areas, which are critical
for reward and memory. We focused our investigation on the expression of
NMDA and AMPA receptor subunits, their scaffolding proteins SAP102 and
SAP97, vesicular and membrane glutamate transporters vGluT1 and GLT-1,
and critical structural components such as proteins involved in
morphology and function of glutamatergic synapses, PSD95 and Arc/Arg3.1.
Our findings demonstrate that a brief EE exposure induces metaplastic
changes in glutamatergic mPFC, NAc, and Hipp. Such changes are
area-specific and involve postsynaptic NMDA/AMPA receptor subunit
composition, as well as changes in the expression of their main
scaffolding proteins, thus influencing the retention of such receptors
at synaptic sites.
Our data indicate that brief EE exposure is sufficient to dynamically
modulate the glutamatergic synapses in mPFC-NAc-Hipp circuits, which may
modulate rewarding and memory processes.