The potency of D-1 and D-2 receptor antagonists is inversely related to the reward value of sham-fed corn oil and sucrose in rats

Weatherford, Sally C.; Greenberg, Danielle; Gibbs, James; Smith, Gerard P.

doi:10.1016/0091-3057(90)90341-e

Cited by 42 publications

(32 citation statements)

References 19 publications

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“…The lack of effect on the 18% fat diet may have been due to the relatively low dosage used. Higher dosages of raclopride (0.2-0.4-mg/kg) produced a dose-related inhibition of corn oil sham-feeding (Weatherford et al, 1990;1988), indicating the involvement of D2 receptors in the positive reinforcing effects of orosensory stimulation by fats. In a real-feeding study, raclopride (∼0.3 mg/kg) reduced consumption of a shorteningbased high-fat diet (33% shortening) when rats were given daily 2-hr access to the diet (Baker et al, 2001).…”

Section: Raclopride: Dopamine D 2 -Like Antagonistmentioning

confidence: 90%

“…One study, which made use of the sham-feeding binge protocol, showed a dose-related inhibition of 100% corn oil sham-feeding with peripheral administration of the D 2 antagonist raclopride, but not the D 1 antagonist SCH23390 (Weatherford et al, 1990). More recent work using real-feeding has shown that higher dosages of peripherally administered raclopride decrease intake of powdered chow mixed with shortening (33% shortening by weight), while lower dosages stimulate intake (Baker et al, 2001).…”

Section: Introductionmentioning

confidence: 99%

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Baclofen, raclopride, and naltrexone differentially reduce solid fat emulsion intake under limited access conditions

Rao

Wojnicki

Coupland

et al. 2008

Pharmacology Biochemistry and Behavior

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Previous work in rats has demonstrated that an Intermittent (Monday, Wednesday, Friday) schedule of access promotes binge-type consumption of 100% vegetable shortening during a 1-hour period of availability. The present study used novel shortening-derived stable solid emulsions of various fat concentrations. These emulsions were the consistency of pudding and did not demonstrate oil and water phase separation previously reported with oil-based liquid emulsions. Male Sprague-Dawley rats were grouped according to schedule of access (Daily or Intermittent) to one of three concentrations (18%, 32%, 56%) of solid fat emulsion. There were no significant Intermittent vs. Daily differences in amount consumed, due to high intakes in all groups. This indicated the acceptability of the emulsions. Baclofen (GABA-B agonist) and raclopride (D2-like antagonist) both significantly reduced emulsion intake in all Daily groups, but only in the 56% fat Intermittent group. Naltrexone (opioid antagonist), in contrast, significantly reduced 32% and 56% fat emulsion intake in the Intermittent, as well as the Daily groups. These results indicate that the fat intake reducing effects of GABA B activation and D2 blockade depend upon fat concentration and schedule of fat access, while the fat intake reducing effects of opioid blockade depend upon fat concentration but not schedule of access.

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Section: Raclopride: Dopamine D 2 -Like Antagonistmentioning

confidence: 90%

Section: Introductionmentioning

confidence: 99%

Baclofen, raclopride, and naltrexone differentially reduce solid fat emulsion intake under limited access conditions

Rao

Wojnicki

Coupland

et al. 2008

Pharmacology Biochemistry and Behavior

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“…Our present findings that both D1 and D2 antagonists reduced operant performance on PR schedule further supports a proposed role for dopamine in reward in general and in sucrose reward in particular (28,50,59), and extends it to obesity. Specifically, systemic administration of dopamine antagonists suppressed both real and sham feeding of sucrose (50) as well as oils (58). Conversely, D1 receptor agonist SKF38393 enhances preference for high-palatability, energydense foods (14).…”

Section: Discussionmentioning

confidence: 99%

Obese OLETF rats exhibit increased operant performance for palatable sucrose solutions and differential sensitivity to D2 receptor antagonism

Hajnal

Acharya

Grigson

et al. 2007

American Journal of Physiology-Regulatory, Integrative and Comp

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Hajnal A, Acharya NK, Grigson PS, Covasa M, Twining RC. Obese OLETF rats exhibit increased operant performance for palatable sucrose solutions and differential sensitivity to D2 receptor antagonism. Am J Physiol Regul Integr Comp Physiol 293: R1846-R1854, 2007. First published September 5, 2007; doi:10.1152/ajpregu.00461.2007.-CCK-1-receptor-deficient Otsuka Long-Evans Tokushima fatty (OLETF) rats are hyperphagic and exhibit a greater preference for sucrose compared with lean controls [Long-Evans Tokushima Otsuka (LETO)]. To directly assess motivation to work for sucrose reward in this model of obesity and type 2 diabetes, we examined the operant performance of OLETF rats at nondiabetic and prediabetic stages (14 and 24 wk of age, respectively) on fixed-ratio (FR) and progressiveratio (PR) schedules of reinforcement. To evaluate the involvement of dopamine systems, the effects of the D1 receptor antagonist SCH23390 (100 and 200 nmol/kg ip) and the D2 receptor antagonist raclopride (200 and 400 nmol/kg ip), were also tested on PR responding for sucrose. Compared with age-matched LETO rats, 14-wk-old OLETF rats emitted more licks on the "active" empty spout operant on the FR-10 schedule of reinforcement to obtain 0.01 M and 0.3 M sucrose and completed higher ratio requirements on the PR schedule to gain access to 0.3 M and 1.0 M sucrose. At 24 wk, this effect was limited to 1.0 M sucrose. Both antagonists were potent in reducing operant responding to 0.3 M sucrose in both strains at both ages, and there was no strain effect to SCH23390 at either age. OLETF rats, on the other hand, showed an increased sensitivity to the higher dose of raclopride, resulting in reduced responding to sucrose reinforcement at 24 wk. Taken together, these findings provide the first direct evidence for an increased motivation for sucrose reward in the OLETF rats and suggest altered D2 receptor regulation with the progression of obesity and prediabetes. dietary obesity; food reward; appetite; palatability; operant lick task THE EPIDEMIC OF OBESITY AND its associated health consequences represent a major cause of preventable morbidity and mortality in the United States and worldwide (31). Although the etiology of obesity is complex, the motivation to respond to palatable food correlates with obesity (3, 52, 60). Despite this relationship, little is known about food reward functions in the obese. The common view is that obese individuals are presumed to show enhanced liking for palatable foods. Several human studies investigating the relationship between preference and obesity support this notion, whereas others debate it (3,19,20,38).Due to the complexity of human eating behavior there has been growing interest in using animal models to decipher basic neural processes underlying the development of obesity. Our laboratory has been investigating the Otsuka Long-Evans Tokushima fatty (OLETF) rats that lack the CCK-1 receptor, are hyperphagic, obese, and gradually develop non-insulin-dependent diabetes mellitus (36). Unlike in other geneticall...

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“…Dopamine is released from the nucleus accumbens and the dorsal striatum in response to intake of palatable foods such as sugar (35). The hypothalamus has also been cited as a site of dopamine action in response to sucrose intake (36)(37)(38)(39). Though dopamine has many actions in the brain, actions relating to intake will be the focus of this review.…”

Section: Dopaminementioning

confidence: 99%

Effects of sugar solutions on hypothalamic appetite regulation

Colley¹,

Castonguay²

2015

Physiology & Behavior

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There are multiple hypotheses for the causes of the obesity epidemic. One such hypothesis is that dietary intake patterns have significantly shifted to include unprecedented amounts of refined sugar. We set out to determine some the unique metabolic changes that occur with initial exposure to dilute glucose, sucrose, high fructose corn syrup, or fructose solutions. Rats were given access to food, water and a sugar solution for 24 h, after which blood and tissues were collected. Fructose access (as opposed to other sugars investigated) resulted in a doubling of circulating triglycerides. Glucose consumption resulted in upregulation of 7 satiety related hypothalamic peptides whereas changes in gene expression were mixed for remaining sugars. Also, following multiple verification assays, 6 satiety related peptides were verified as being affected by sugar intake. These data provide evidence that not all sugars are equally effective in affecting the control of intake.

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The potency of D-1 and D-2 receptor antagonists is inversely related to the reward value of sham-fed corn oil and sucrose in rats

Cited by 42 publications

References 19 publications

Baclofen, raclopride, and naltrexone differentially reduce solid fat emulsion intake under limited access conditions

Baclofen, raclopride, and naltrexone differentially reduce solid fat emulsion intake under limited access conditions

Obese OLETF rats exhibit increased operant performance for palatable sucrose solutions and differential sensitivity to D2 receptor antagonism

Effects of sugar solutions on hypothalamic appetite regulation

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