Obesity in Osborne-Mendel and S 5B/Pl rats: effects of sucrose solutions, castration, and treatment with estradiol or insulin

Schemmel, Rachel; Teague, R.J.; Bray, George A.

doi:10.1152/ajpregu.1982.243.3.r347

Cited by 18 publications

(17 citation statements)

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“…It is, thus, possible that some of the changes in sucrose drinking observed in the present results are also due to the unconditioned regulation of food intake produced by estrogen receptor activation. Results of an earlier study showed that the unconditioned effects of estradiol on ingestion, after 5 consecutive days of estradiol injections (0.1-1 mg per rat) in OVX-female rats, were absent 3 days after cessation of treatment (Schemmel et al, 1982). This minimizes the likelihood that any unconditioned effects contributed to the observed reduction in sucrose drinking in the present study as a 5 day intertrial interval was used.…”

Section: Discussionmentioning

confidence: 93%

“…Conditioning Days 1-3 and the Test Day were each separated by 5 days. The results of a prior study have established that the separation period between the conditioning days and the test day in the present study is sufficient to eliminate any unconditioned effects of estradiol (Schemmel et al, 1982). Water baseline training was conducted until each animal drank a minimum of 7 ml of water in the lickometer apparatus.…”

Section: Water Deprivation and Sucrose Drinkingmentioning

confidence: 86%

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Tamoxifen and raloxifene produce conditioned taste avoidance in female rats: A microstructural analysis of licking patterns

et al. 2009

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Section: Discussionmentioning

confidence: 93%

Section: Water Deprivation and Sucrose Drinkingmentioning

confidence: 86%

Tamoxifen and raloxifene produce conditioned taste avoidance in female rats: A microstructural analysis of licking patterns

et al. 2009

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“…2,3,16 There are few studies, however, that have actually compared obese to lean rats maintained on an HCD. The limited evidence indicates that hyperinsulinemia and hyperleptinemia are evident in obese animals whether on an HFD or HCD, [23][24][25] while dietary fat is a critical stimulus for producing hyperglycemia as well as hyperphagia. 26 In contrast, sucrose-or starch-rich diets reveal in obese rats increased carbohydrate metabolism in muscle, which is not evident in obese animals on an HFD.…”

Section: Introductionmentioning

confidence: 99%

Different forms of obesity as a function of diet composition

et al. 2005

Int J Obes

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OBJECTIVE:To characterize the phenotype of obesity on a high-carbohydrate diet (HCD) as compared to a high-fat diet (HFD) or moderate-fat diet (MFD). METHODS AND PROCEDURES:In four experiments, adult Sprague-Dawley rats (275-300 g) were maintained for several weeks on a: (1) HFD with 50% fat; (2) balanced MFD with 25% fat; or (3) HCD with 10% fat/65% carbohydrate. Then, based on the amount of body fat accumulated in four dissected fat pads, the animals were subgrouped as lean (lowest tertile) or obese (highest tertile) and characterized with multiple measures. RESULTS: The obese rats of these diet groups, with 70-80% greater body fat than the lean animals, exhibited elevated levels of leptin and insulin and increased activity of lipoprotein lipase in adipose tissue (aLPL), with no change in muscle LPL. Characteristics common to the obese rats on the HFD or MFD, but not seen on the HCD, were hyperphagia, elevated circulating levels of triglycerides (TG), nonesterified fatty acids (NEFA) and glucose, and a significant increase in b-hydroxyacyl-CoA dehydrogenase (HADH) activity in muscle, reflecting its greater capacity to metabolize fat. This was accompanied by a significant increase in expression of the peptide, galanin (GAL), in the paraventricular nucleus (PVN), as measured by in situ hybridization and real-time quantitative PCR, and also in GAL peptide immunoreactivity. These measures of GAL were consistently, positively correlated with circulating TG levels and also with HADH activity in muscle. In contrast to these fatassociated changes, rats that became obese on an HCD maintained normal caloric intake and levels of TG, NEFA, and glucose. They also showed no change in PVN GAL mRNA or peptide. Instead, they exhibited a significant reduction in HADH activity compared to the lean animals, along with increased activity of phosphofructokinase in muscle, a key enzyme in glycolysis. CONCLUSION: Specific characteristics of obesity, including expression of hypothalamic peptides, are dependent upon diet composition. Whereas obesity on an HFD is associated with hyperphagia and elevated lipids, fat metabolism in muscle, and fatstimulated peptides such as GAL, obesity on an HCD with a similar increase in body fat shows none of these characteristics and instead exhibits a metabolic pattern in muscle that favors carbohydrate over fat oxidation. These results suggest the existence of multiple forms of obesity with different underlying mechanisms that are diet dependent.

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“…This concern is especially valid given that intake measures were taken every 72 h and it is well known that the unconditioned effects of estradiol are observed for 24 h or more after estradiol administration and can last for days (see Geary, 2004 for review). However, it also has been reported that after 5 consecutive days of estradiol injections (0.1-1mg per rat) in OVX-female rats the unconditioned effects of estradiol on ingestion are no longer observed 3 days after the cessation of treatment (Schemmel et al, 1982). According to these results, it is highly unlikely that the present reductions in intake are solely the result of the unconditioned effects of estradiol as all experimental days were conducted 3 days apart.…”

Section: Discussionmentioning

confidence: 99%

Tamoxifen produces conditioned taste avoidance in male rats: An analysis of microstructural licking patterns and taste reactivity

Fudge¹,

Kavaliers²,

Baird³

et al. 2009

Hormones and Behavior

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Estrogen receptor activation has been shown to reduce body weight and produce a conditioned reduction in food intake in male rats that is putatively mediated by estradiol's suggested aversive effects. Evidence has shown that the selective estrogen receptor modulator tamoxifen used in the prevention and treatment of breast cancer may also produce a change in food intake and body weight, which are known to impact cancer development and survival. The purpose of the present study was to examine whether tamoxifen produces a conditioned reduction in intake similar to estradiol by producing a conditioned aversion. A one bottle lickometer test was used to examine conditioned changes in sucrose drinking, while the taste reactivity test was used to measure rejections reactions, which serve to index aversion in rats. A backward conditioning procedure that consisted of 3 conditioning days and one vehicle test day was used to examine for conditioned changes in 0.3 M sucrose intake and taste reactivity. Our results show that tamoxifen produced a conditioned reduction in sucrose drinking in a one bottle fluid intake test that was similar to the effects produced by estradiol (positive control); however, no active rejections reactions were produced by either tamoxifen (1 and 10 mg/kg) or estradiol. The present results suggest that tamoxifen, at the doses used in the present study, acts as an estrogen receptor agonist to regulate food intake and that the conditioned reduction in intake produced by tamoxifen and estradiol reflects conditioned taste avoidance rather than conditioned taste aversion.

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Obesity in Osborne-Mendel and S 5B/Pl rats: effects of sucrose solutions, castration, and treatment with estradiol or insulin

Cited by 18 publications

References 0 publications

Tamoxifen and raloxifene produce conditioned taste avoidance in female rats: A microstructural analysis of licking patterns

Tamoxifen and raloxifene produce conditioned taste avoidance in female rats: A microstructural analysis of licking patterns

Different forms of obesity as a function of diet composition

Tamoxifen produces conditioned taste avoidance in male rats: An analysis of microstructural licking patterns and taste reactivity

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