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. Author manuscript; available in PMC: 2019 Nov 21.
Published in final edited form as: Neuroscience. 2018 Oct 11;393:236–257. doi: 10.1016/j.neuroscience.2018.10.002

Fig. 12. Schematic illustrating sex differences in the hippocampal opioid system in saline-injected (control) and oxycodone condition place preference (CPP) rats.

Fig. 12.

Red arrows indicate predicted effects of delta opioid receptor (DOR) and mu opioid receptor (MOR) trafficking changes on excitation (plus signs) and inhibition (minus signs) in the CA3 and dentate gyrus (DG). #1–4 indicate points where there are differences in the distribution of DORs and MORs in saline-injected and oxycodone CPP rats. gc, granule cell; hil, hilus; lpp, lateral perforant path; ML, molecular layer; mf, mossy fiber; SLu, stratum lucidum; SR, stratum radiatum. Blue color = MORs; Green color = Leu-Enkephalin (LEnk) levels; orange color = DORs. Circles = plasmalemmal receptors; squares = near-plasmalemmal receptors; crosses = cytoplasmic receptors.

1. Sal-females compared to Sal-males have fewer near-plasmalemmal and total DORs in SR CA3 pyramidal cell dendrites.

2. Oxy-females compared to Sal-females have more DORs in the spines of SR CA3 dendrites. Oxy-males compared to Sal-males have fewer near plasmalemmal DORs in SR CA3 dendrites and more DORs in the spines of CA3 pyramidal cells contacted by mossy fibers. Oxy-males compared to Sal-males also have greater LEnk levels in mossy fibers.

3. Sal-females compared to Sal-males have elevated plasmalemmal DORs on the dendrites of GABAergic-labeled interneurons previously shown to colocalize somatostatin and neuropeptide Y (Commons and Milner, 1996; Williams and Milner, 2011). Sal-females compared to Sal-males have fewer plasmalemmal MORs on the dendrites of parvalbumin (PARV)-containing interneurons.

4. In Oxy-females, near-plasmalemmal DORs increase in GABA-labeled dendrites and plasmalemmal and total MORs increase in PARV-labeled dendrites. Moreover, the number of DOR-immunoreactive hilar interneurons is increased in Oxy-females compared to Sal-females.