Sucrose produces withdrawal and dopamine-sensitive reinforcing effects in planarians - PubMed (original) (raw)

Sucrose produces withdrawal and dopamine-sensitive reinforcing effects in planarians

Charlie Zhang et al. Physiol Behav. 2013.

Abstract

Sucrose produces physical dependence and reinforcing effects in rats. We hypothesized that similar effects could be demonstrated in planarians, the earliest animal with a centralized nervous system. We used two assays, one that quantifies withdrawal responses during drug absence as a reduction in motility and another that quantifies reinforcing effects using a conditioned place preference (CPP) design. In withdrawal experiments, planarians exposed to sucrose (1%) for 60 min and then tested in water for 5 min displayed reduced motility compared to water controls. Acute or continuous sucrose (1%) exposure did not affect motility. CPP experiments used a biased design to capitalize upon planarians' natural preference for the dark (pretest, sucrose conditioning in the light, posttest). Planarians conditioned with sucrose (1%) displayed a greater preference shift than sucrose-naïve planarians. Glucose (0.1, 1%), but not the non-digestible disaccharide lactulose (0.1, 1%), also produced a greater preference shift than water-exposed planarians. Development of sucrose-induced CPP was inhibited when sucrose (1%) conditioning was conducted in combination with dopamine receptor antagonists SCH 23390 (1 μM) or sulpiride (1 μM). These results suggest that the rewarding and reinforcing effects of sugar are highly conserved across species and that planarians offer an invertebrate model to provide insight into the pharmacological effects of sucrose and related sweeteners.

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Figures

Fig. 1

Fig. 1

Sucrose produces withdrawal responses following discontinuation of exposure. Planarians exposed to sucrose (S) (1%) or water (W) for 60 min were removed and tested in S (1%) or W for 5 min. Data are presented as motility counts + S.E.M. (1A) or number of head-bops + S.E.M. (1B). N = 10 planarians/group. *p < 0.05 compared to W/W group.

Fig. 1

Fig. 1

Sucrose produces withdrawal responses following discontinuation of exposure. Planarians exposed to sucrose (S) (1%) or water (W) for 60 min were removed and tested in S (1%) or W for 5 min. Data are presented as motility counts + S.E.M. (1A) or number of head-bops + S.E.M. (1B). N = 10 planarians/group. *p < 0.05 compared to W/W group.

Fig. 2

Fig. 2

Sucrose and glucose, but not lactulose, produce CPP. Data are presented as the mean preference score (s) + S.E.M. (difference between post-conditioning and pre-conditioning times) from planarians in which (A) sucrose (SUC) (0, 0.1, 1, 10%), (B) glucose (0, 0.1, 1%) or (C) lactulose (0, 0.1, 1%) was paired with ambient light during the conditioning phase. N = 8–10 planarians per group. **p < 0.01 compared to W in the respective experiments.

Fig. 2

Fig. 2

Sucrose and glucose, but not lactulose, produce CPP. Data are presented as the mean preference score (s) + S.E.M. (difference between post-conditioning and pre-conditioning times) from planarians in which (A) sucrose (SUC) (0, 0.1, 1, 10%), (B) glucose (0, 0.1, 1%) or (C) lactulose (0, 0.1, 1%) was paired with ambient light during the conditioning phase. N = 8–10 planarians per group. **p < 0.01 compared to W in the respective experiments.

Fig. 2

Fig. 2

Sucrose and glucose, but not lactulose, produce CPP. Data are presented as the mean preference score (s) + S.E.M. (difference between post-conditioning and pre-conditioning times) from planarians in which (A) sucrose (SUC) (0, 0.1, 1, 10%), (B) glucose (0, 0.1, 1%) or (C) lactulose (0, 0.1, 1%) was paired with ambient light during the conditioning phase. N = 8–10 planarians per group. **p < 0.01 compared to W in the respective experiments.

Fig. 3

Fig. 3

Dopamine D1 or D2 receptor antagonists significantly inhibit development of CPP induced by 1% sucrose (SUC). 3A) D1 antagonist effects: CPP was determined in planarians that were conditioned with water (W), SCH, SUC, or SCH + SUC in the ambient light. 3B) D2 antagonist effects: CPP was determined in planarians that were conditioned with water (W), SUL, SUC, or SUL + SUC in the ambient light. Data are presented as the mean preference score (s) + S.E.M. (difference between post-conditioning and pre-conditioning times). N = 10 planarians per group. **p < 0.01, *p < 0.05 compared to W or SUC.

Fig. 3

Fig. 3

Dopamine D1 or D2 receptor antagonists significantly inhibit development of CPP induced by 1% sucrose (SUC). 3A) D1 antagonist effects: CPP was determined in planarians that were conditioned with water (W), SCH, SUC, or SCH + SUC in the ambient light. 3B) D2 antagonist effects: CPP was determined in planarians that were conditioned with water (W), SUL, SUC, or SUL + SUC in the ambient light. Data are presented as the mean preference score (s) + S.E.M. (difference between post-conditioning and pre-conditioning times). N = 10 planarians per group. **p < 0.01, *p < 0.05 compared to W or SUC.

Fig. 4

Fig. 4

Dopamine D1 or D2 receptor antagonists do not affect expression of CPP induced by 1% sucrose (SUC). 4A) D1 antagonist effects: Following a pre-test in drug-naïve planarians, conditioning with water (W) or sucrose (SUC) was conducted in the ambient light. A post-test was conducted in which planarians from both groups (W and SUC) were exposed to W or SCH. 4B) D2 antagonist effects: Experiments were conducted as described in Panel A except that SUL was used instead of SCH. Data are presented as the mean preference score (s) + S.E.M. (difference between post-conditioning and pre-conditioning times). N = 10 planarians per group. *p < 0.05 compared to respective W/W group.

Fig. 4

Fig. 4

Dopamine D1 or D2 receptor antagonists do not affect expression of CPP induced by 1% sucrose (SUC). 4A) D1 antagonist effects: Following a pre-test in drug-naïve planarians, conditioning with water (W) or sucrose (SUC) was conducted in the ambient light. A post-test was conducted in which planarians from both groups (W and SUC) were exposed to W or SCH. 4B) D2 antagonist effects: Experiments were conducted as described in Panel A except that SUL was used instead of SCH. Data are presented as the mean preference score (s) + S.E.M. (difference between post-conditioning and pre-conditioning times). N = 10 planarians per group. *p < 0.05 compared to respective W/W group.

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