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. Author manuscript; available in PMC: 2014 Jan 23.
Published in final edited form as: Psychopharmacology (Berl). 2011 Mar 5;216(3):367–378. doi: 10.1007/s00213-011-2225-4

Fig 3.

Fig 3

Food-maintained operant behavior under the FR 1 (a) and the PR (b) schedule of reinforcement in M4−/− mice (white) and wildtype littermates (black). Abscissas: Concentration of liquid food in water. Ordinates: Reinforcers earned under the FR 1 (reinforcers per hour, a) and under the PR (breaking point, b) schedule of reinforcement. The final ratio corresponding to each breaking point is indicated in parentheses for the PR schedule. Group means were calculated from the average for each mouse of two determinations per concentration evaluated according to a Latin square design. Group sizes: FR 1 schedule: n = 10-13; PR schedule: n = 9-10. The M4−/− mice did not differ from their wildtype littermates in food-maintained responding under the FR 1 schedule. Under the PR schedule of reinforcement M4−/− mice reached higher breaking points at a concentration of 3% liquid food. **p < 0.01 vs. wildtype; post-hoc t-test following overall significant genotype effect in two-way ANOVA.