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. 2016 Nov 10;5:37–53. doi: 10.1016/j.ynstr.2016.11.002

Fig. 10.

Fig. 10

Schematic shows sex differences in the hippocampal opioid system in unstressed, acute and chronic stressed rats. Arrows indicate predicted effects of DOR trafficking changes on inhibition (minus signs) in the CA3 and dentate gyrus (DG). # 1–5 indicate points where there are sex differences in the DOR distribution in unstressed rats and after AIS and CIS. Bt = basket cell terminals; mf = mossy fiber terminals; plasma membrane = PM. Green color indicates enkephalin levels. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)
  • (1) In unstressed conditions, DORs are increased in CA3 pyramidal cell dendritic spines (Harte-Hargrove et al., 2015) and decreased near the plasmalemma of the shafts of CA3 dendrites in high estrogen (proestrus) females compared to males. Moreover, low frequency (1 Hz) stimulation of the granule cells elicits a DOR-dependent LTP in CA3 of proestrus females that is not seen in diestrus females or males (Harte-Hargrove et al., 2015).
  • (2) After AIS, DORs decrease in the cytoplasm of CA3 dendritic shafts in females but increase in the near plasmalemma compartment of dendritic shafts and spines contacted by mossy fibers of CA3 pyramidal cells in males;
  • (3) After CIS, DORs decrease in the cytoplasm of dendritic shafts and spines contacted by mossy fibers in CA3 pyramidal cells in females and decrease near the plasma membrane of CA3 neuron dendritic shafts in males. Males, but not females, display an atrophy of CA3 pyramidal cell dendrites following (McEwen, 1999).
  • (4) Previous studies have shown that DORs are primarily in GABAergic dendrites containing NPY/SOM (Commons and Milner, 1996a, Williams and Milner, 2011, Williams et al., 2011b). GABAergic NPY/SOM interneurons are known to project to granule cell dendrites where they converge with entorhinal afferents from the lateral perforant path (lpp) (Sperk et al., 2007). After AIS, DORs in GABAergic interneuron dendrites decrease near the plasma membrane in females but increase near the plasmalemma in males.
  • (5) After CIS, DORs in GABAergic interneuron dendrites increase near the plasma membrane in females but decrease near the plasmalemma in males. The number of NPY-containing neurons decreased in CIS males but not CIS females (not shown).