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. 2016 Apr 26;7:109. doi: 10.3389/fphar.2016.00109

FIGURE 1.

FIGURE 1

(Top) The self-administration behavior of a chocolate-flavored beverage in Wistar rats. Rats were trained to lever-respond for the chocolate-flavored beverage [5% (w/v) Nesquik® chocolate powder in water] under the Fixed Ratio (FR) 10 schedule of reinforcement in daily 60 min self-administration sessions. During these 20 daily self-administration sessions (maintenance phase), self-administration behavior stabilized in all rats. Each point of this panel is the mean ± SEM of n = 30 rats. (Center) The extinction responding behavior. The extinction responding phase occurred after the self-administration maintenance phase. During the sessions of the extinction responding phase, lever-responding was unreinforced (the chocolate-flavored beverage was unavailable). Based on the number of lever-responses for the chocolate-flavored beverage over the last five sessions of the maintenance phase, rats were divided into the three groups (n = 10) that – after completion of the extinction responding phase – received the three different doses of Phaseolus vulgaris. Each point of this panel is the mean ± SEM of sample sizes varying between 1 and 10, depending on the session in which each single rat achieved the extinction criterion (i.e., ≤30 lever-responses per session for three consecutive sessions). (Bottom) The effect of treatment with different doses of a dry extract of P. vulgaris (Beanblock) on reinstatement of seeking for the chocolate-flavored beverage. This test session occurred once each single rat had achieved the extinction criterion. In the reinstatement session (lasting 60 min and occurring the day after the extinction responding phase), unreinforced lever-responding was reinstated by the repeated presentation of a complex of gustatory, olfactory, auditory, and visual stimuli previously associated to availability of the chocolate-flavored beverage. P. vulgaris dry extract was administered intragastrically, at doses of 0, 100, and 500 mg/kg, 120 min before the start of the session. Each bar of this panel is the mean ± SEM of n = 10 rats. ∗P < 0.05, ∗∗P < 0.01, and ∗∗∗P < 0.0005 in comparison to the same rat group in the last session of the extinction responding phase (Newman–Keuls test); #P < 0.005 in comparison to the vehicle-treated rat group in the reinstatement session (Newman–Keuls test).