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PubMed2005

[Effects of Bt corn straw decomposition on soil enzyme activities and soil fertility].

An incubation test with the straws of Bt corn 34B24 and its non-transgenic isogenic line 34B23, Bt corn Nongda 61, and non-transgenic Nongda 3138 was conducted to study the potential effects of Bt corn straw decomposition on soil enzyme activities and soil fertility. No significant difference in soil protease and acid phosphatase activities was found between treatments 34B24 and 34B23; but on day 75 of incubation, soil dehydrogenase activity was significantly higher in treatment 34B24 than in treatment 34B23. The same was true for soil invertase activity on days 15,45, 60 and 75. Soil urease activity in treatment 34B24 was significantly increased on day 30, but decreased on days 45 and 75. A significant difference in several soil enzyme activities was also observed between the treatments of two Bt corn hybrids and their conventional cultivars at some sampling days. After incubation for 90 days, the contents of soil available P and K were significantly lower in treatment 34B24 than in treatment 34B23. The differences mentioned above resulted from the composition of test corn straws, which may be affected by the Bt gene transformation process. In order to accurately assess the effects of Bt corn straw decomposition on soil ecosystem, a standard classification system of soil enzyme activities should be established for different soil types from different regions.

Fertilizers↗
PubMed1991

Transformations of alpha-linolenic acid in leaves of corn (Zea mays L.).

Short incubation of [1-14C]alpha-linolenic acid with whole homogenate of leaves of corn (Zea mays L.) led to the formation of 4 major lipoxygenase products, i.e. 12-oxo-13-hydroxy-9(Z),15(Z)-octadecadienoic acid, 12-oxo-10,15(Z)-phytodienoic acid (12-oxo-PDA), 9(R,S)-hydroxy-12-oxo-10(E),15(Z)-octadecadienoic acid, and 13-oxo-9,11-tridecadienoic acid. Trapping experiments demonstrated transient appearance of the unstable allene oxide, 12,13(S)-epoxy-9(Z),11,15(Z)-octadecatrienoic acid, precursor of the three first mentioned compounds. The major lipoxygenase products formed from endogenous alpha-linolenic acid upon homogenization of corn leaves were identified as 12-oxo-13-hydroxy-9(Z),15(Z)-octadecadienoic acid (11.4 +/- 2.4 micrograms/g) and 12-oxo-PDA (5.8 +/- 1.2 micrograms/g). Steric analysis showed that 12-oxo-PDA formed from endogenous alpha-linolenic acid was largely the natural 9(S),13(S) enantiomer. Thus, corn leaves, like seeds of corn, contain hydroperoxide dehydrase and allene oxide cyclase. However, the lipoxygenase of corn leaves specifically catalyzed oxygenation of the 13 (omega 6) position of alpha-linolenic acid and thus differed from the previously recognized corn seed lipoxygenase which is specific for the 9 position.

Fatty Acids, Unsaturated↗
PubMed2006

[Carbon balance analysis of corn fuel ethanol life cycle].

The quantity of greenhouse gas emissions (net carbon emissions) of corn-based fuel ethanol, which is known as an alternative for fossil fuel is an important criteria for evaluating its sustainability. The methodology of carbon balance analysis for fuel ethanol from corn was developed based on principles of life cycle analysis. For the production state of fuel ethanol from summer corn in China, carbon budgets in overall life cycle of the ethanol were evaluated and its main influence factors were identified. It presents that corn-based fuel ethanol has no obvious reduction of carbon emissions than gasoline, and potential improvement in carbon emission of the life cycle of corn ethanol could be achieved by reducing the nitrogen fertilizer and irrigation electricity used in the corn farming and energy consumption in the ethanol conversion process.

Carbon↗
PubMed1990

[Enrichment of precooked white corn flour (Zea mays) with amaranth seed flour (Amaranthus sp.)].

Three mixtures of precooked white corn flour with 10, 20 and 30% amaranth flour were prepared. The sedimentation and consistency of the mixtures differed from those of the white corn flour, but without altering the capacity of dough formation to prepare arepas. The protein, fiber, and ash contents were higher than those of the precooked white corn flour. The functional properties of water and oil absorption increased in 20 and 10%, respectively. During the three-month storage, the protein and fat contents were not altered. Acceptability tests of the arepas were carried out and results indicated that those mixtures prepared with 10% and 20% substitution levels were acceptable from the sensory point of view. The protein quality was analyzed in terms of protein efficiency ratio (PER), which proved to be higher than that of the commercial white corn flour (PER 1.93), and the apparent digestibility was 92%. As far as lysine is concerned, results showed that arepas prepared with the mixture containing 10% amaranth (1.6 g lysine/100 g protein) and 20% (2.0 g lysine/100 g protein) also proved to be higher than the commercial white corn flour arepas (0.7 g lysine/100 g protein). Based on the above findings, enrichment of commercial white corn flour with grain amaranth flour, prior to the preparation of arepas, a product of high consumption in Venezuela as part of the habitual diet, is recommended.

Amaranthus↗
PubMedDate not supplied

Enzyme-linked immunosorbent assay of aflatoxin B1 in naturally contaminated corn and cottonseed.

Naturally contaminated corn and cottonseed samples were screened for aflatoxin B1 (AFB1) by a direct competitive enzyme-linked immunosorbent assay (ELISA). Samples were blended 5 min in an extraction solvent of methanol-water-dimethylformamide (70 + 29 + 1) and filtered. Filtrates were assayed by direct competition between AFB1 in the corn and cottonseed samples and AFB1-peroxidase conjugate for binding to specific antibody adsorbed to a solid phase microtiter plate. Standard curves prepared using the extract of AFB1-free corn and cottonseed samples, and extraction solvent only, showed negligible interference by the sample extract in the performance of ELISA. The AFB1 content in corn and dehulled cottonseed samples as determined by ELISA ranged from 7 to 422 micrograms/kg and 7 to 3,258 micrograms/kg, respectively. When ELISA estimates of AFB1 in corn were compared with values obtained by thin layer chromatography (CB method), the correlation coefficient (n = 10) was 0.95. Average interassay and subsample coefficients of variation for ELISA in corn were 21.4 and 22.0%, respectively. When ELISA estimates of AFB1 in cottonseed were compared with values obtained by liquid chromatography (Pons method), the correlation coefficient (n = 15) was 0.96. Using this ELISA, 36 duplicate sample extracts can be screened for AFB1 in less than 2 h.

Aflatoxin B1↗
PubMed1987

The mouse bioassay for the detection of estrogenic activity in rodent diets: III. Stimulation of uterine weight by dextrose, sucrose and corn starch.

We have shown previously that mice fed the American Institute of Nutrition (AIN-76A) purified diet experience a significant increase in uterine:body weight (U:BW) ratios when compared to the U:BW ratios of mice fed a closed formula natural ingredient diet (Certified Rodent Chow #5002) for 7 days. The AIN-76A purified diet contains 5% corn oil and 65% carbohydrates with 50% of the carbohydrates coming from sucrose or dextrose and 15% from corn starch. The objective of this study was to determine whether the fat and carbohydrate content contributed to the unexpected uterine growth promoting activity observed in mice fed the AIN-76A diet. Estrogen bioassays were performed using CD-1 mice weaned at 15 days of age and assigned randomly to the negative control diet (Certified Rodent Chow #5002) or to the positive control diet (#5002) containing 4 or 6 ppb DES for comparison or to the test diets. The test diets were prepared by adding sucrose, dextrose, corn starch, corn oil or soybean oil to the #5002 negative control diet at 10% w/w concentration. Uterine:BW ratios were determined at 7 days post-feeding. The uterine weights and the U:BW ratios of mice fed the test diets containing dextrose, corn starch, or corn oil, were increased significantly (P less than 0.05) over those of mice fed the negative control diet. The uterine weights and U:BW ratios of mice fed the test diets containing sucrose or soybean oil also were increased over those of mice fed the negative control diet. These increases in uterine weights and U:BW ratios were similar to the increases in uterine weights and U:BW ratios of mice fed the positive control diet containing 4 ppb DES. It was concluded that the fats and carbohydrates caused preferential increases in uterine weights and in U:BW ratios and may account for the estrogen-like uterine growth promoting activity observed in mice fed the AIN-76A purified diet.

Animal Feed↗
PubMed1983

Five-year study of mycotoxins in Virginia wheat and dent corn.

Every year during the 5-year period 1976-1980, approximately 100 samples each of corn and wheat from trucks delivering the grains at elevators in Virginia were collected by personnel of the Federal Grain Inspection Service and shipped to NRRC. Samples were analyzed as soon as possible for aflatoxin, zearalenone, and ochratoxin A. The 3 mycotoxins were not detected in any wheat sample. Zearalenone and ochratoxin A were not found in any corn sample; however, aflatoxin was detected in at least 25% of the corn samples from every crop year. In 1976-1980, the incidence of aflatoxin at levels of 20 ng/g or more (the Food and Drug Administration guideline) ranged from 18 to 61%; aflatoxin incidence above 100 ng/g was 5-29%. The average aflatoxin levels in corn samples collected in the 5 years varied from 21 to 137 ng/g. Moisture content of the samples was not determined, so aflatoxin levels given may be higher than they were at harvest. However, there are obviously differences from year to year. In freshly harvested corn samples collected by fieldmen of the Statistical Reporting Service in yield surveys in 1978 and 1979, aflatoxin incidence above the FDA guideline was 10 and 13%, and above 100 ng/g was 4 and 7%. The average aflatoxin level in all samples collected in 1978 was 13 ng/g and in 1979, 36 ng/g. Some aflatoxin can be expected yearly in Virginia corn, but the incidence and levels vary from year to year.

Food Contamination↗
PubMed1982

Detoxification of aflatoxin contaminated corn by methanol extraction.

Corn containing 500 ppb aflatoxin was decontaminated by methanolic extraction. Ninety percent of the aflatoxin was removed in one three-minute blending with a solvent to corn ratio of 4:1. Recycling methanol for additional extractions could be done by removal of aflatoxin by carbon or distillation of the methanol. Methanol costs per bushel of corn without recycling would probably be expensive. By recycling, the cost is estimated to be ten to twenty cents per bushel in a laboratory size experiment. A source of ethanol on the farm could make the process more feasible. Chicks fed decontaminated corn showed no signs of aflatoxin toxicity. Fatty degenerated livers were produced in chicks fed the nondetoxified corn. Other mycotoxins which are not affected by the ammoniation process used to decontaminate corn, can be removed by this process.

Aflatoxins↗
PubMed1994

Oral corn pollen hypersensitivity in Arizona Native Americans: some sociologic aspects of allergy practice.

Thirty-three Navajo patients were seen in a private allergy consultation practice in Flagstaff, Arizona between 1978 and 1990. Sufficient skin test and historical data were available from nine atopic patients to evaluate hypersensitivity reactions to oral corn pollen used in the Navajo ceremonials. Six of the nine patients had positive skin test reactions to corn pollen and four of these six reported symptoms from oral corn pollen. The symptoms included various combinations of oral and ear itching, sneezing, cough, and wheezing. One corn pollen skin test-negative patient reported slight throat itching from the pollen. In no case did the patient or referring primary care physician associate the symptoms with ceremonial oral corn pollen use. This is the first report of hypersensitivity reactions to the ceremonial use of oral corn pollen in native Americans.

Administration, Oral↗
PubMed1996

Effect of corn peptide on alcohol metabolism and plasma free amino acid concentrations in healthy men.

OBJECTIVES: To determine the influence of corn peptide on the reduction of the increase in blood ethanol level in healthy adult men after intake of alcohol at a dose of a 0.5 g per kg of body weight. SUBJECTS: Twenty healthy male volunteers participated in the study. DESIGN: The study was performed as a cross-over design. The subjects ingested corn peptide, and 30 min later alcohol was given. The blood ethanol and plasma free amino acids were analyzed at fixed times during a 2 h observation period after the alcohol intake. RESULTS: In subjects not given corn peptide, the blood ethanol concentration reached the maximum level of 9.35 mM at 30 min after alcohol intake, then gradually decreased. In addition, the plasma free amino acid levels decreased after alcohol intake. When subjects were given 3 and 5 g corn peptide 30 min prior to the alcohol intake, a significant reduction of the increase in blood ethanol levels of 3.7 mM and 2.83 mM was observed. In subjects given 5 g corn peptide, the plasma alanine, leucine, proline and free amino acid levels significantly elevated and remained at a high level during a 2 h observation period after alcohol intake. CONCLUSION: These results indicate that the ingestion of corn peptide reduces the increase in blood ethanol level after alcohol intake and causes the elevation in plasma amino acids alanine, leucine, and proline.

Administration, Oral↗
PubMed1997

[The effect of lime cooking of corn on phytic acid, calcium, total and ionizable iron content].

The present study was carried out with the objective to learn about the effect of the nixtamalization process of corn on the content of phytic acid and availability of iron in the lime-cooked corn. For the study, lots of corn with 0, 0.4, 0.8 and 1.20% of lime on the basis of corn weight, in water in the ratio of 3 to 1, and cooking times at each level of lime of 55, 65 and 75 minutes, were processed. Half of the treatments were not soaked after cooking, while the other half were soaked in the cooking solution for a 12-hour period. Statistical analysis of the data and correlations calculated showed that the phytic acid content decreased significantly during the nixtamalization process, affected by the cooking time and the level of lime used, reaching levels of reduction of around 35%. Both the ionizable iron and calcium level increased up to 52-77% and 400-478% respectively. The amount of calcium present in the cooked corn as the result of the lime cooking process, is significantly higher in comparison with the phytic acid content, which may be easily saturated and thus, unavailable to bind iron. An inverse relationship was found between phytic acid and bioavailable iron and its absorption percentage. On the other hand, soaking time did not significantly affected the phytic acid and available iron, although it contributed to a slightly higher Ca accumulation. The amount of ionizable iron was higher at higher levels of lime, which suggested that the nixtamalization process would favor the biological utilization of iron in lime-cooked corn and provide calcium to the diet.

Analysis of Variance↗
PubMed1997

Chloroform in drinking water prevents hepatic cell proliferation induced by chloroform administered by gavage in corn oil to mice.

Chloroform administered by gavage in corn oil, but not when administrated in drinking water, has been shown to induce liver cancer in female B6C3F1 mice and to enhance cell proliferation. Since humans are exposed to chloroform in their drinking water, we evaluated whether exposure by this route would interact with the activity of chloroform when administered by gavage in corn oil. Female B6C3F1 mice were exposed to chloroform in drinking water for 33 days at 0, 300, or 1800 ppm (Experiment 1) or for 31 days at 0, 120, 240, or 480 ppm (Experiment 2) and for 3 days prior to termination also received a daily dose of 263 mg/kg chloroform administered by gavage in corn oil. Exposure to chloroform in drinking water reduced both the hepatotoxicity and the enhanced cell proliferation (bromodeoxyuridine-labeling index and mitotic index) elicited in response to chloroform administered by gavage in corn oil. Hence, chloroform administered in drinking water reduced the activity of chloroform administered by gavage in corn oil, suggesting that it would also reduce the hepatocarcinogenic activity of chloroform administered by gavage.

Administration, Oral↗
PubMed1989

Effects of fish oil, corn oil and lard diets on lipid peroxidation status and glutathione peroxidase activities in rat heart.

In this study, we investigated the effect of various types of fats on heart lipid peroxidation status and on blood lipid parameters. Rats were fed either a low-fat diet (2.2% lard plus 2.2% corn oil), a corn oil diet (17%), a salmon oil diet (12.5%) supplemented with 4.5% corn oil, or a lard diet (15%) supplemented with 2% corn oil. All diets were supplemented with 1% cholesterol. Rats were fed for eight weeks. When compared with the low-fat diet, the salmon oil-diet intake resulted in a lower blood cholesterol, triglyceride and phospholipid concentrations (-50, -56 and -30%, respectively). Corn oil only tended to lower blood lipids; this decrease was significant for triglycerides only (-40%). The hypocholesterolemic effect of salmon oil diet is even more pronounced, if blood cholesterol values are compared with those of rats fed the lard diet. Heart lipid composition was not affected by dietary manipulations. Fatty acid composition of cardiac phosphatidylcholines and phosphatidylethanolamines, however, were altered by high-fat diets. In phosphatidylcholine, salmon oil induced a twelvefold decrease in the n-6/n-3 ratio and a 26% increase in the unsaturation index. For phosphatidylethanolamine, the n-6/n-3 ratio decreased 7.7-fold and the unsaturation index increased by 13%. A 50% decrease of the n-6/n-3 ratio was observed in animals fed the lard diet. Ultramicroscopic examination of ventricles revealed that those of the salmon oil group significantly accumulated lipofuscin-like or ceroid material, whereas this accumulation was barely detectable in hearts of the other groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1988

Effects of dietary corn oil and salmon oil on lipids and prostaglandin E2 in rat gastric mucosa.

Three groups of male rats were fed either a corn oil-enriched diet (17%, w/w), a salmon oil-enriched diet (12.5%) supplemented with corn oil (4.5%) or a low-fat diet (4.4%) for eight wk to investigate the possible relationships between dietary fatty acids and lipid composition, and prostaglandin E2 level and phospholipase A2 activity in the rat gastric mucosa. High-fat diets induced no important variation in total protein, phospholipid and cholesterol contents of gastric mucosa. Compared with a low-fat diet, corn oil produced a higher n-6/n-3 ratio in mucosal lipids, whereas this ratio was markedly lowered by a fish oil diet. In comparison with the low-fat diet, the production of prostaglandin E2(PGE2) in gastric mucosa of rats fed salmon oil was significantly decreased by a factor of 2.8. In the corn oil group, PGE2 production tended to decrease, but not significantly. In comparison with the low-fat diet, both specific and total gastric mucosal phospholipase A2 activities were increased (+ 18 and 23%, respectively) in the salmon oil group; they were unchanged in the corn oil group. It is suggested that the decrease of gastric PGE2 in rats fed fish oil is not provoked by a decrease in phospholipase A2 activity but may be the result of the substitution of arachidonic acid by n-3 PUFA or activation of PGE2 catabolism.

Animals↗
PubMed1999

Impact of diets with corn oil or olive/sunflower oils on DNA damage in healthy young men.

BACKGROUND: Plant fats and oils are major sources of mono- and polyunsaturated fatty acids as well as vitamin E, the major fat-soluble antioxidants in human nutrition. Dietary antioxidants are expected to reduce cancer risk by minimizing DNA damage. AIM OF THE STUDY: To compare the effects of gamma-tocopherol rich corn oil and the mixture of the alpha-tocopherol rich olive/sunflower oil on plasma concentration of tocopherols and on the frequency of sister chromatid exchange (SCE), an indicator of DNA damage. METHODS: This study had a double-blind, cross-over design and was conducted in 20 normal healthy non-smoking males aged 19-31 years. Design included a 2-week adjustment period and two 2-week test periods in which diets containing 30% energy as fat including either 80 g of corn oil (CO) (20 mg alpha-tocopherol, 100 mg gamma-tocopherol) or 80 g of olive/ sunflower oil (OSO) (24 mg alpha-tocopherol, 2.4 mg gamma-tocopherol), as the main fat-source, were given. Blood samples for analysis of SCE rate and content of tocopherols were collected at the beginning (T0), after adjustment (T1) and after the test period (T2) in intervals of 2 weeks. RESULTS: After two weeks of the corn oil diet, the plasma concentration of gamma-tocopherol increased but alpha-tocopherol decreased significantly compared to the olive/sunflower oil diet. The concentration of alpha-tocopherol increased (CO: 22.99 +/- 1.11 vs. OSO: 24.40 +/- 1.49 micromol/l) and that of gamma-tocopherol decreased (CO: 4.19 +/- 0.29 vs. OSO: 2.99 +/- 0.25 micromol/l) after the olive/sunflower oil diet. Intake of the corn oil diet was associated with reduced SCE rate and intensity, whereas there was no change in SCE after the olive/sunflower oil diet (CO: 7.66 +/- 0.25 vs. OSO: 8.06 +/- 0.47 mean SCE/cell) CONCLUSIONS: The combination of gamma-tocopherol with alpha-tocopherol in corn oil diet despite the lower alpha-tocopherol equivalents/diene acid equivalents ratio achieved better protection against DNA damage than alpha-tocopherol alone in the olive/sunflower oil diet.

Adult↗
PubMed1996

Distinct responses of mouse hepatic CYP enzymes to corn oil and peroxisome proliferators.

We studied the response of male DBA/2N mouse liver monooxygenases to acute (one-day) and subacute (7-day) exposure to clofibrate, gemfibrozil, and corn oil. The day following a single treatment with clofibrate (200 mg/kg), coumarin 7-hydroxylase (COH) activity decreased significantly (by 70%) with a concomitant decrease in the CYP2A4/5 protein and mRNA levels. The 7-day treatment schedule also decreased COH activity by only by 30%, though the levels of CYP2A4/5 protein and mRNA were still low. Treatment 1 and 7-day with clofibrate decreased 7-pentoxyresorufin O-dealkylase (PROD) activity by 40%. No changes were seen in testosterone 15 alpha-hydroxylase (T15 alpha OH) activity after 1 day of treatment with clofibrate but, after 7 days, it was decreased by 50%. Clofibrate treatment had no significant effects on testosterone 7 alpha-hydroxylase (T7 alpha OH), 7-ethoxyresorufin O-deethylase (EROD), or benzphetamine N-demethylase (BZDM) activities. Gemfibrozil (200 mg/kg) did not alter COH activity or CYP2A4/5 protein content after a single treatment, but a slight decrease was seen in the mRNA level. Treatment for 7 days significantly increased (2.5-fold) the activity and mRNA content but the amount of protein remained unchanged. Gemfibrozil enhanced (2-2.7-fold PROD and EROD (2-2.5-fold) activities by both treatments, whereas T15 alpha OH, T7 alpha OH, or BZDM activities were not significantly affected. Treatment with corn oil for 7 days significantly decreased (65%) COH activity and CYP2A4/5 protein and mRNA levels. PROD (55%) and T15 alpha OH (65%) activities were significantly decreased even after a single dose although injection for 7 days had no effect. Neither of the corn oil schedules had any marked effect on T7 alpha OH, EROD, or BZDM activities. These results demonstrate: 1. a decrease in the expression of CYP2A4/5 gene by clofibrate and corn oil; 2. substantial differences within the CYP2A subfamily in their responses to corn oil, clofibrate, and gemfibrozil; and 3. distinct responses of other xenobiotic metabolizing CYP subfamily enzymes to clofibrate and gemfibrozil.

Animals↗
PubMed1991

Application of molecular encapsulation for toxicology studies: toxicokinetics of p-chloro-alpha,alpha,alpha-trifluorotoluene in alpha-cyclodextrin or corn oil vehicles in male F344 rats.

Toxicokinetics of p-chloro-alpha,alpha,alpha-trifluorotoluene (CTFT) after administration as an aqueous alpha-cyclodextrin (alpha-CD) molecular encapsulation suspension (alpha-CD vehicle) or as a corn oil solution (corn oil vehicle) were compared. Male F344 rats were administered intragastrically CTFT in alpha-CD vehicle or corn oil vehicle at dose levels of 10, 50, or 400 mg/kg. Other male F344 rats were administered CTFT intravenously in a 10% Tween 80 aqueous solution. Serial blood samples were taken from a cannulated jugular vein for up to 52 hr after dosing and the CTFT concentrations in whole blood were determined by gas chromatography. The biological elimination half-life of CTFT from the center compartment was not affected by the vehicle used; however, absorption of CTFT from the alpha-CD vehicle was much faster than from the corn oil vehicle. The average absorption half-lives from the alpha-CD vehicle and corn oil vehicle were 17 and 98 min, respectively. Despite the differences in absorption, no statistical difference was observed in the calculated areas under the blood concentration versus time curves (AUC) obtained from rats dosed with either vehicle. Dose proportionality for CTFT was established up to 400 mg/kg and bioavailability was shown to be complete for both vehicles.

Administration, Oral↗
PubMed1990

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.

Intraperitoneal injection of 50 micrograms.kg-1 of the selective dopamine D-1 receptor antagonist, SCH 23390, significantly decreased sham feeding of 6% and 10% sucrose solutions, but not sham feeding of 100% corn oil. Intraperitoneal injection of raclopride, a D-2 antagonist, elicited a significant dose-dependent (200-400 micrograms.kg-1) decrease in sham intake of both sucrose concentrations and corn oil at doses that did not increase the latency to sham feed or produce overt motor impairment. The rank order of inhibitory potency for both SCH 23390 and raclopride was 6% sucrose greater than 10% sucrose greater than 100% corn oil. In a second experiment, we found that in 2-bottle preference tests, the rank order of preference for these three liquids was 100% corn oil greater than 10% sucrose greater than 6% sucrose. Assuming that preference measured the relative reward value of the liquids, the potencies of the two antagonists were inversely related to the reward value of the liquid that was sham fed. This result supports but does not prove the dopamine hypothesis of the positive reinforcing effect of orosensory stimulation by nutrients. In addition, the differential selectivity of the two antagonists for different classes of nutrients suggests that normal sensory and/or hedonic processing of sham-fed sucrose depends on stimulation of both D-1 and D-2 receptors, but the normal sensory and/or hedonic processing of sham-fed corn oil depends primarily, perhaps exclusively, on stimulation of D-2 receptors.

Animals↗