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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. 2. Effects of oxycodone conditioned place preference (CPP) on the levels of Leu-Enkephalin-immunoreactivity (LEnk-ir) in the mossy fiber pathway.

Fig. 2.

A. Low magnification photomicrograph of the rat dorsal hippocampus shows LEnk-ir in the mossy fiber pathway within stratum lucidum of CA3a,b and c and in the crest (cr), central hilus (ch), and dorsal blade (db) of the dentate gyrus (DG). The region of CA3 stratum oriens (SO) sampled is also indicated. B. High magnification photomicrograph of LEnk-ir in stratum lucidum of CA3b in Sal-male and Oxy-male rats. C. Sal-females (estrus) compared to Sal-males have higher levels of LEnk-ir in the dorsal blade, central hilus and crest of the DG. D. Oxy-females compared to Sal-females demonstrate decreased levels of LEnk-ir in CA3a. Oxy-males compared to Sal-males show significantly increased levels of LEnk-ir in the CA3b. E. High magnification photomicrograph of CA3a shows greater LEnk-ir levels in stratum lucidum in a Sal-female compared to an Oxy-female. However, greater densities of LEnk-ir are detected in SO of Oxy-females compared to Sal-females. F. Oxy-females (OF) compared to Sal-females (SF) have an increased density of LEnk-labeled mossy fibers in SO of CA3. SM = saline males; OM = Oxy males **p < 0.01, *p < 0.05; N = 5–6 rats per group. Scale bars: A, 500 µm; B & E = 100 µm