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. Author manuscript; available in PMC: 2019 May 29.
Published in final edited form as: Psychopharmacology (Berl). 2017 Sep 15;234(23-24):3499–3506. doi: 10.1007/s00213-017-4734-2

Figure 1: Effect of Environmental Enrichment on Acquisition of Remifentanil Self-Administration.

Figure 1:

Active lever presses (A) and inactive lever presses (C) during the self-administration phase of acquisition by rats trained with 1 μg/kg/infusion remifentanil. Active lever presses (B) and inactive lever presses (D) by rats trained with 3 μg/kg remifentanil. Enr: gray triangles (n = 7 for 1 μg/kg; n = 5 for 3 μg/kg), Std: black squares (n = 7 for 1 μg/kg; n = 5 for 3 μg/kg), Iso: white circles (n = 7 for 1 μg/kg; n = 5 for 3 μg/kg). Note the difference in scales between the upper and lower panels.