[Enriched environment reduces pyramidal neuron excitability in the anterior cingulate cortex to alleviate restraint stress-induced anxiety-like behaviors in mice].

Objectives: To investigate the mechanism by which the pyramidal neurons of the anterior cingulate cortex (ACC) modulate the effects of enriched environment (EE) for relieving anxiety-like behaviors in mice.

Methods: C57BL/6J mice were randomly divided into control group, restraint stress (RS) group, and RS+EE group (=8). The mice in the latter two groups were subjected to RS for 2 h daily for 3 days, and those in RS+EE group were housed in an EE during modeling. Anxiety-like behaviors of the mice were evaluated using the elevated plus-maze tests (EPM) and open field test (OFT). Changes in c-Fos expression in the ACC of the mice were detected with immunofluorescence assay, and pyramidal neuron excitability in the ACC (Pyn) was measured using patch-clamp technique. The miniature excitatory and inhibitory postsynaptic currents (mEPSC and mIPSC, respectively) were analyzed to assess synaptic transmission changes.

Results: Behavioral tests showed obvious anxiety-like behaviors in RS mice, and such behavioral changes were significantly improved in RS+EE mice. Immunofluorescence staining revealed significantly increased c-Fos expression in the ACC in RS mice but lowered c-Fos expression in RS+EE group. Compared with the control mice, the RS mice showed increased action potential firing rate of Pyn, which was significantly reduced in RS+EE group. Compared with the RS mice, the RS+EE mice showed also decreased frequency of mEPSCs of Pyn, but the amplitude exhibited no significant changes. No obvious changes in the frequency or amplitude of mIPSCs were observed in RS+EE mice.

Conclusions: EE reduces excitability of Pyn to alleviate anxiety-like behaviors induced by RS in mice.