The endocannabinoid system (ECS) has recently gained interest as a promising therapeutic target for chronic pain treatment. An emerging body of research has revealed that the ECS interacts with the endogenous opioid system in a variety of complex processes. However, pain research has historically excluded female animals and failed to consider sex differences. This project aims to investigate whether morphine administration has a sexually dimorphic effect on type 1 cannabinoid receptors (CB1) in the ventral tegmental area (VTA) and amygdala of mice. These brain regions have been selected due to their role in both addiction and the emotional aspect of pain, which appear to be sexually dimorphic phenomena. Using reverse transcriptase qPCR, this study aims to determine (i) whether chronic morphine treatment impacts CB1 expression in the VTA and amygdala and (ii) whether this treatment differentially impacts male and female animals.