3.4.1. β-Catenin

Following the behavioral battery (Figure 4a) and the sacrifice of the rats, the expression of β-catenin was measured in the mPFC (Figure 5a), NAc (Figure 5b), CA1 (Figure 5c), and BLA (Figure 5d). A two-way ANOVA on β-catenin levels revealed significant main effects of shock [mPFC: F(1,30) = 13.278, *p* < 0.01; NAc: F(1,31) = 11.402, *p* < 0.01] and virus [BLA: F(1,31) = 11.593; CA1: F(1,31) = 9.944, all *p* < 0.01], as well as a shock × virus interaction [mPFC: F(1,30) = 13.781, *p* < 0.01; NAc: F(1,31) = 9.515, *p* < 0.01; CA1: F(1,31) = 19.697, *p* < 0.001]. Post hoc analysis revealed decreased β-catenin levels in the mPFC, NAc, and CA1 in the Shock/GFP group compared with the NoShock/GFP group (mPFC, *p* < 0.001; NAc and CA1, both *p* < 0.01) and the Shock/OE group (mPFC, *p* < 0.05; Nac and CA1, both *p* < 0.001). Additionally, in the CA1 the Shock/OE group demonstrated increased expression compared to the NoShock/OE group (*p* < 0.05), and in the BLA, the Shock/OE group demonstrated increased expression compared to the Shock/GFP group (*p* < 0.01). Hence, exposure to shock and reminders downregulated β-catenin levels in the mPFC, Nac, and CA1, and overexpressing β-catenin in the NAc normalized these effects.

For β-actin levels, no significant between-group differences were observed in any of these brain areas, suggesting that β-actin levels were not affected by the treatment.

**Figure 5.** β-catenin, mGluR5, and CB1 receptors regulation by overexpressing nucleus accumbens (NAc) β-catenin in rats exposed to shock and reminders. β-catenin expression (**<sup>a</sup>**–**d**): The Shock/GFP (green fluorescent protein) group demonstrated a significant decrease in β-catenin levels compared with NoShock/GFP and Shock/OE (overexpression) groups in the medial prefrontal cortex (mPFC) (**a**), nucleus accumbens (NAc) (**b**), and CA1. Additionally, in the CA1, the Shock/OE group demonstrated increased expression compared to the NoShock/OE group (**c**); in the basolateral amygdala (BLA), the Shock/OE group demonstrated increased expression compared to the Shock/GFP group (**d**). Metabotropic glutamate receptor subtype 5 (mGluR5) expression (**<sup>e</sup>**–**h**): The Shock/GFP group

demonstrated a significant decrease in mGluR5 levels compared with the NoShock/GFP and Shock/OE groups in the mPFC (**e**) and NAc. Additionally, in the NAc, the NoShock/GFP group demonstrated increased expression compared with the NoShock/OE group (**f**); in the CA1, the NoShock/GFP group demonstrated decreased expression of mGluR5 compared to the NoShock/OE and Shock/GFP groups (**g**); in the BLA, no significant differences in mGluR5 levels were observed (**h**). Cannabinoid receptor type 1 (CB1r) expression (**i**,**j**): the Shock/GFP group demonstrated increased levels of CB1r compared with the NoShock/GFP and Shock/OE groups in the mPFC (**i**); and NAc (**j**) (data is shown as mean ± sem; \*, *p* < 0.05; \*\*, *p* < 0.01; \*\*\*, *p* < 0.001).
