A. In large PARV-labeled dendrites, Oxy-CIS males showed increased density of plasmalemmal MOR-SIG particles compared to Sal-CIS males. B. No significant differences between groups were observed in near plasmalemmal MOR-SIG particles in large PARV-labeled dendrites. C. In large PARV-labeled dendrites, Oxy-CIS females showed increased density of cytoplasmic MOR-SIG particles compared to Oxy-CIS males. D. Sal-CIS females compared to Sal-CIS males had a trend toward higher total densities of MOR-SIG particles in total PARV-labeled dendrites. Additionally, compared to Oxy-CIS males, Oxy-CIS females showed a significant increase in total MOR-SIG particle density within total PARV-labeled dendrites. SF, Sal-female; SM, Sal-male; OF, Oxy-female; OM, Oxy-male. **p < 0.01, *p ≤ 0.05, ^p = 0.066; N = 3 rats per group; n = 50 dendrites per rat.