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. Author manuscript; available in PMC: 2019 Mar 1.
Published in final edited form as: Psychopharmacology (Berl). 2017 Dec 2;235(3):861–871. doi: 10.1007/s00213-017-4804-5

Figure 1.

Figure 1

Experimental timeline showing the approximate age in days (± 2) of rats in the adolescent- and adult-onset groups for cannulation surgery and self-administration procedures. Acquisition of METH self-administration was assessed in groups of rats trained at 0.02, 0.05, or 0.08 mg/kg/inf unit doses. Acquisition of 0.1% oral saccharin self-administration was assessed in a fourth group. Progressive ratio (PR) responding, which was assessed only in rats that met acquisition criterion at 0.08 mg/kg/inf, was tested at four doses (0.02, 0.05, 0.08, 0.1 mg/kg/inf) in separate sessions that each were separated by a maintenance session of 0.08 mg/kg/inf available on an FR5 schedule.