Sucrose Taste Research Articles

Depressive symptoms and alterations in sucrose taste perception: cognitive bias or a true change in sensitivity?

Previous studies have reported elevated taste thresholds in depressed subjects, but those studies did not control for changes in response bias. The current study used signal detection analyses to address this shortcoming. Sucrose detection thresholds were measured (1) in subjects with high and low Hamilton Depression Rating Scale (HAM-D) scores who did not meet standard criteria for current Major Depressive Episode (MDE); and (2) in subjects who did fulfil standard criteria for MDE. Subjects with low HAM-D scores produced significantly more false alarms than the other two groups, but taste sensitivity, as indexed by d', did not vary significantly across groups. These results suggest that changes in response bias underlie previously reported increases in sucrose taste thresholds in depressed subjects.

Oestradiol-induced taste avoidance is the result of a conditioned palatability shift.

Taste avoidances were conditioned in male rats by pairing ingestion of a novel sucrose (0.3 M solution) taste with injections of 17 beta oestradiol (100 micrograms kg-1, s.c.). Following conditioning and prior to a two-bottle choice test (sucrose vs water), taste reactivity responses to three 30 s intraoral sucrose infusions were quantified. A robust conditioned shift in palatability, consisting of reduced ingestive and increased aversive taste reactivity responses, was obtained in the oestradiol group but not the vehicle control group. This conditioned palatability shift was also reflected in subsequent strong avoidance of the sucrose solution in the two-bottle choice test. The findings that oestradiol can condition taste aversions and shift food preferences support a role for oestrogens in the production of anorexia.

Effects of natural and synthetic neuroactive substances on the growth and feeding of cabbage looper, Trichoplusia ni

AbstractIn this study we investigated the effects of two naturally occurring beta‐carboline alkaloids and two synthetic tricyclic antidepressants on the growth and food consumption of fifth instar larvae of the cabbage looper, Trichoplusia ni Hübner (Lepidoptera: Noctuidae). In artificial diets at high concentrations (3,000 ppm), harmane, amitriptyline, and imipramine reduce growth and feeding; harmane reduced feeding consistently at a lower concentration (200 ppm). In animals other than insects, beta‐carboline alkaloids inhibit monoamine oxidase (MAO) activity and thus affect rates of disposition of serotonin and other monoamine neurotransmitters. Because brain serotonin levels are associated with variation in rates of carbohydrate and protein intake in insects, the effects of beta‐carboline alkaloid ingestion on dietary self‐selection behavior were examined. Choosing between diets lacking carbohydrate but containing protein and diets lacking protein but containing carbohydrate, larvae consumed a greater proportion of diet containing protein but lacking carbohydrate in the presence of harmane than in its absence. These results are consistent with beta‐carboline alkaloid‐mediated persistence of serotonin in the brain due to MAO inhibition. Alternatively, these results could reflect alkaloid‐mediated peripheral inhibition of sucrose taste receptors influencing ingestive behaviors. That beta‐carboline alkaloid ingestion is associated with changes in feeding behavior is consistent with a possible defensive role for these compounds in plant foliage.

Olfactory neuronal responses in the primate orbitofrontal cortex: analysis in an olfactory discrimination task

1. The primate orbitofrontal cortex receives inputs from the primary olfactory (pyriform) cortex and also from the primary taste cortex. To investigate how olfactory information is encoded in the orbitofrontal cortex, the responses of single neurons in the orbitofrontal cortex and surrounding areas were recorded during the performance of an olfactory discrimination task. In the task, the delivery of one of eight different odors indicated that the monkey could lick to obtain a taste of sucrose. If one of two other odors was delivered from the olfactometer, the monkey had to refrain from licking, otherwise he received a taste of saline. 2. Of the 1,580 neurons recorded in the orbitofrontal cortex, 3.1% (48) had olfactory responses and 34 (2.2%) responded differently to the different odors in the task. The neurons responded with a typical latency of 180 ms from the onset of odorant delivery. 3. Of the olfactory neurons with differential responses in the task, 35% responded solely on the basis of the taste reward association of the odorants. Such neurons responded either to all the rewarded stimuli, and none of the saline-associated stimuli, or vice versa. 4. The remaining 65% of these neurons showed differential selectivity for the stimuli based on the odor quality and not on the taste reward association of the odor. 5. The findings show that the olfactory representation within the orbitofrontal cortex reflects for some neurons (65%) which odor is present independently of its association with taste reward, and that for other neurons (35%), the olfactory response reflects (and encodes) the taste association of the odor. The additional finding that some of the odor-responsive neurons were also responsive to taste stimuli supports the hypothesis that odor-taste association learning at the level of single neurons in the orbitofrontal cortex enables such cells to show olfactory responses that reflect the taste association of the odor.

DOES MATURE HINDMILK TASTE CALM CRYING INFANTS? † 79

In human newborns, sucrose taste arrests crying and increases mouthing and hand-mouth contact, but colostrum and mature foremilk does not. To determine if mature hindmilk taste has similar effects, 20 normal 10 day old infants who were crying spontaneously for ≥ 15 consecutive seconds were randomized to receive 250 ul of their mother's hindmilk X 5 at 30 second intervals by pipette to the midline anterior tongue prior to one feed and water prior to another. Per cent time crying, mouthing, and hand-mouth contact were calculated for baseline (used as a covariate), administration intervals and up to three minutes following administration. Crying reduction was similar for both liquids during administration (67 vs. 63%), remained less in each minute following breast milk (74, 74, 71%), but increased (73, 83, 89%) following water (solution X period interaction: F[6, 114]=2.5;P=.03). Mouthing was elevated during administration (29% for both), but returned to baseline (< 13%) within two minutes (period effect F[5,90]=2.9;P=.02). There was no change in hand-mouth contact.

Area postrema mediates the formation of rapid, conditioned palatability shifts in lithium-treated rats.

The rapid acquisition and subsequent retention of lithium-induced conditioned changes in taste reactivity responses to sucrose were examined in rats with the area postrema (AP) either ablated or intact. On 2 conditioning days, a series of brief intraoral sucrose infusions was paired with the effects of LiCl or NaCl injections. Repeated associations of the sucrose taste with the effects of lithium significantly reduced ingestive responses and increased aversive responses only in the AP-intact group. AP-ablated rats treated with LiCl and rats injected with NaCl displayed an ingestive pattern of responses. Only the AP-intact rats, previously injected with LiCl, subsequently displayed evidence of a conditioned taste aversion. We conclude that toxin activation of the AP is required to produce the conditioned shift in taste reactivity responses and subsequent expression of a taste aversion in rats treated with lithium.

Odor preference in honeybees as a function of amount of reward: Tests of two explanations

How does a foraging honeybee come to prefer a color or odor paired with the large of two amounts of sucrose solution to a color or odor paired with the smaller amount? One hypothesis is that the attractiveness of a color or odor is based on the strength of its association with the taste of sucrose, which increases with the duration of concurrent color-taste or odor-taste stimulation. Another hypothesis is that the attractiveness of a color or odor is based on association with the afferent consequences of feeding, which are different for the two amounts. Both hypotheses were tested in experiments on proboscis-extension conditioning, a technique that provides better control of stimulation than is possible in work with free-flying foragers. In Experiments 1–3, which were designed to test the first hypothesis, an odor that accompanied the ingestion of sucrose on training trials was found to elicit extension of the proboscis when subsequently it was presented alone, but the duration of concurrent stimulation had no significant effect on the probability or persistence of the response. In Experiments 4 and 5, which were designed to test the second hypothesis, an odor that immediately followed the ingestion of sucrose on training trials failed to elicit extension of the proboscis when subsequently it was presented alone. The results support neither hypothesis.

Area postrema mediates the formation of rapid, conditioned palatability shifts in lithium-treated rats.

The rapid acquisition and subsequent retention of lithium-induced conditioned changes in taste reactivity responses to sucrose were examined in rats with the area postrema (AP) either ablated or intact. On 2 conditioning days, a series of brief intraoral sucrose infusions was paired with the effects of LiCl or NaCl injections. Repeated associations of the sucrose taste with the effects of lithium significantly reduced ingestive responses and increased aversive responses only in the AP-intact group. AP-ablated rats treated with LiCl and rats injected with NaCl displayed an ingestive pattern of responses. Only the AP-intact rats, previously injected with LiCl, subsequently displayed evidence of a conditioned taste aversion. We conclude that toxin activation of the AP is required to produce the conditioned shift in taste reactivity responses and subsequent expression of a taste aversion in rats treated with lithium.

Toxin-induced conditioned changes in taste reactivity and the role of the chemosensitive area postrema

Conditioned taste avoidances (CTAs) are an important component of behavioral regulation of ingestion. In the laboratory CTAs can be produced by pairing a novel taste stimulus with the physiological feedback produced by a toxin, such as lithium. Such toxins putatively activate a chemosensitive brainstem structure, the area postrema, which ultimately results in the production of a CTA. The present review describes a series of studies which examined conditioned changes in taste reactivity responses (TRRs) when a novel intraoral sucrose taste was paired with the effects of an intraperitoneal (IP) injection of LiCl, and the role of the area postrema in the formation of conditioned palatability shifts. It was first of all necessary to examine the effects of area postrema ablations on TRRs to a range of intraoral sucrose and quinine stimulus intensities. In the first study area postrema lesioned rats exhibited concentration dependent changes in TRRs to these taste stimuli that were very similar to those exhibited by sham lesioned rats. The second study demonstrated that 30 s intraoral infusions of sucrose (0.3 M), presented at 5 or 10 min intervals following an IP injection of LiCl (3.0 meq), resulted in conditioned changes in TRRs. These were characterized by orderly, gradual reductions in ingestive responses and increases in aversive responses. Finally, when area postrema lesioned rats (Study 3) were subjected to this conditioning procedure (brief sucrose presentations paired with the effects of LiCl) no evidence for conditioned or unconditioned changes in TRRs to sucrose were obtained. Lesioned rats injected with LiCl behaved similarly to sham lesioned rats injected with NaCl. These series of studies provide evidence indicating that the chemosensitive area postrema mediates the formation of conditioned palatability shifts induced by treatment with a toxin such as lithium.

Gustatory detection thresholds after parabrachial nuclei lesions in rats.

Rats with either electrolytic (Experiment 1) or excitotoxic lesions (Experiment 2) that had been electrophysiologically centered in the gustatory zone of the parabrachial nuclei (PBN) were tested for sucrose and NaCl taste detection thresholds in a conditioned avoidance task. With 1 exception, all of these rats had previously shown severe deficits in acquiring an LiCl-based conditioned taste aversion (CTA) to sucrose, NaCl, or alanine. The rats with excitotoxic lesions also had failed to express a depletion-induced sodium appetite. Despite the uniformity of these deficits, the rats with lesions exhibited varied performance in the detectability task. Roughly 1/3 of the rats did not perform competently, 1/3 had elevated thresholds, and 1/3 showed no or only marginal impairments in taste detectability. These findings demonstrate that the elimination of CTA following PBN lesions is not necessarily linked to an impairment in taste signal detection. Thus, PBN-induced deficits on 1 taste-related task do not entirely correspond with impairments on another.

Sweetener blending: How sweet it is!: How combinations of sweeteners recreate the taste of sucrose in reduced-sugar food products

It may seem that sweetener blending is a new food technology, but blends of nutritive sweeteners, such as sucrose and high-fructose corn syrup, are common ingredients in product formulations. The latest trend in sweetener blending is to combine nonnutritive high-intensity sweeteners (eg, acesulfame K and aspartame) or a nonnutritive sweetener and a nutritive sweetener (eg, acesulfame K and sorbitol) in a food product.

Effects of caffeine deprivation on taste and mood.

Despite its ubiquitous consumption in the natural environment, caffeine has not been a reliable reinforcer in laboratory settings. The reinforcing effects of caffeine are greater in caffeine-dependent subjects relative to non-dependent subjects, but the mechanism underlying this difference remains unclear. We hypothesized that deprivation from caffeine would produce alterations in subjective ratings of stimuli commonly associated with caffeine consumption. Specifically, we hypothesized that hedonic ratings of the coffee taste would be selectively enhanced following caffeine deprivation. Twelve regular caffeine users received acute doses of caffeine (300mg) or placebo after 33h of caffeine deprivation or non-deprivation. They rated the taste of coffee and sucrose, saccharin, and quinine solutions on intensity, bitterness, sweetness, pleasantness, and unpleasantness. Contrary to our hypothesis, subjects' ratings of the pleasantness of the coffee taste were not significantly altered by caffeine deprivation. However, subjects' ratings of the bitterness and sweetness of the coffee taste and ratings of the sucrose solution were altered by caffeine. Implications of these data for caffeine self-administration are discussed.

A New Look at Some Old Mechanisms in Human Newborns: Taste and Tactile Determinants of State, Affect, and Action

Three studies of normal human newborns and of newborns of methadone-maintained mothers evaluated how orotactile (pacifier) and orogustatory (sucrose) stimulation, alone and in combination, affected crying behavior, heart rate, gross motor activity, eye opening, and hand-mouth coordination. For each measure of infant state, pacifier and sucrose stimulation each caused significant changes that followed very different time courses. Orotactile (pacifier) stimulation precipitated immediate changes in all behaviors, and, when the pacifier was removed, all behaviors soon reverted to baseline levels. The changes precipitated by orogustatory (sucrose) stimulation were more gradual but extended well beyond the end of sucrose administration. Although both pacifier and sucrose influences are mediated orally as opposed to in the stomach or intestine, the effects involve different brain pathways. The fact that infants born to methadone-maintained mothers did not change their behaviors during or after sucrose administration but that their reactions to pacifier stimulation could not be distinguished from those of normal infants suggests that reactions to sucrose are mediated centrally by endogenous opioids while those to the pacifier work through other central mechanisms. These findings with human newborns are consonant with those of many animal studies that have also shown rapid onset and rapid offset for contact- and suckling-induced behavioral changes, slower onset and slower offset for changes induced by taste, and opioid mediation of changes induced by the taste of sucrose. Orogustatory and orotactile influences on affect, action, and cardiovascular function are discussed from the perspectives of energetics and growth, central determinants of state, motivation, and learning during the newborn period.

Divergent responses to saccharin vs. sucrose availability after stress in rats

Rats were exposed to 100 5-s inescapable, unpredictable shocks then had access to water and saccharin or sucrose solution for 5–6 days. Shock reduced daily drinking during saccharin tests (Experiments 1, 2B, 4) and increased daily drinking during sucrose tests (Experiment 2B). In addition, shock reduced body weight when saccharin, but not when sucrose, was available (Experiments 1, 2B). The specificity of the reductions to saccharin tests (Experiments 2B, 4), equal intake of flavors shortly after stress (Experiments 2B to 4), and failure of saccharin-naive and saccharin-familiar groups to differ (Experiment 3) argue against a neophobia interpretation. Normal or above-normal drinking during sucrose (Experiment 2B) or water-only (Experiment 4) tests indicate an absence of general hedonic, motoric, or hydrational deficits. Qualitative differences in the tastes of saccharin and sucrose may underlie their disparate effects on drinking after shock. Whatever the mechanisms, the present results show that even a severe stressor can decrease or increase ingestion, depending on the flavors available.

Facial expressions and genetic sensitivity to 6- n-propylthiouracil predict hedonic response to sweet

Individuals differ in their hedonic response to sweet: sweet likers show increasing liking with increasing sucrose concentration, while sweet dislikers show increasing dislike with increasing concentration. Our results indicated that naive raters can correctly classify sweet likers and dislikers by observing subjects' facial responses to the taste of sucrose. Also, for both adults and children, the sweet liker/disliker distinction correlated strongly with the genetically determined ability to taste 6- n-propylthiouracil (PROP): PROP nontasters were almost always sweet likers, whereas sweet dislikers were almost always PROP tasters. Sweet dislikers also reported a purer sweet sensation than likers, who perceived nonsweet components in pure sucrose solutions. These results suggest that the sweet liker/disliker distinction is robust and valid, and that sensitivity to PROP may influence preference for sweet by altering the quality of sweet.

Sham feeding in intact and chronic decerebrate rats.

In the traditional sham-feeding paradigm, the amount of sugar solution consumed by the rat is influenced by its concentration and the open or closed condition of the gastric fistula. The present experiments examine: 1) whether sham intake effects obtained under the "intraoral intake" paradigm, developed to explore controls of ingestion in otherwise aphagic preparations such as the decerebrate, are similar to those of previous studies in which intact rats obtained the fluid stimulus by spout licking; and 2) whether chronic decerebrate and intact rats show a similar elevation of their sucrose intake when ingesting with an open (sham intake) vs. closed gastric fistula. Experiment 1 showed that sham intraoral intake exceeded intake in the closed condition only for sucrose concentrations greater than 0.1 M. After it was established that the results obtained with the intraoral paradigm were consistent with those reported in the literature, the new paradigm was applied to the chronic decerebrate rat in experiment 2 to determine whether forebrain structures are necessary for sham-feeding effects. The effect of sucrose concentration and fistula condition on the behavior of chronic decerebrates was similar to that of intact rats. Like intact rats, decerebrate rats consumed more sucrose in the open condition but only for concentrations exceeding 0.1 M. This concentration-dependent sham sucrose intake of chronic decerebrate rats provides compelling evidence that the integration of sucrose's taste and postingestive effects that modulates ingestive behavior can be accomplished by the caudal brain stem.

Study of some factors affecting intensity/time characteristics of sweetness

Intensity/time plots of sweetness produced by d-glucose, d-fructose and sucrose at concentrations ranging from 2.3 to 9.2% (w/v) were recorded for solutions at 15, 22 and 35°C. The intensity ( I) and persistence ( P) power functions were applied to the results obtained with a potentiometer connected to a chart recorder similar to the sensory measurement unit recording flux (SMURF) device. Increasing the concentration of assessed samples leads to an increase of perceived intensity with a tendency to show a compression for d-fructose and sucrose and an expansion for d-glucose. Persistence increases linearly as a function of concentration for the three sugars. Only very slight modification of intensity and persistence are observed when the temperature is varied from 15 to 35°C. Intensity/time plots were also recorded at 22°C for solutions containing 5% sucrose or equisweet concentrations of d-glucose or d-fructose brought to apparent viscosities of 5, 15, 25 and 35 mPa s by addition of maltodextrins. It was found that the sweetness intensity decreases as viscosity increases for d-fructose and sucrose solutions whereas it remains constant for d-glucose. The persistence remains almost constant for the three sugars when the viscosity is varied. The effect of temperature on viscosity coefficients and hydration numbers is measured for the three sugars. A decrease in intrinsic viscosity [η], B-coefficients and hydration numbers is observed with increasing temperature whilst the apparent specific volume is increased. From the Raman spectra of water and aqueous solutions of sugars, it may be concluded that increasing the temperature leads to a lowering of the rigidity of the hydrogen bonded clusters and an increase in mobility of H 2O molecules. The increase in the size of the sugars derived from apparent specific volume (V̄ 2°) values reduces their accessibility to the receptor site. This effect is minimised as regards the perceived sweetness by the increased mobility of water. The effects of concentration, temperature and viscosity on the intensity and persistence of the sweet taste of d-glucose, d-fructose and sucrose, together with their physicochemical properties in dilute solution, suggest that the accessibility of the sweet molecule to the receptor is an important step in the taste chemoreception. This step is followed by a biochemical phenomenon involving opening of ion channels which is sensitive to the mobility of water around the site and the sweetener.

An inhibitor of sweet taste response modulates glucose-induced phosphoinositide breakdown in rat pancreatic islets.

We studied the effect of a specific-competitive inhibitor of the sucrose taste response, p-nitrophenyl-D-glucopyranoside (PNP-Glu) on insulin release and phosphoinositide metabolism in rat pancreatic islets. The alpha-anomer, but not the beta-anomer, of PNP-Glu at a concentration of 5 mM inhibited insulin release induced by 10 mM glucose. Islets were labeled by exposure for 2 h to 10 uCi of myo-[2-3H] inositol solution supplemented with 2.8 mM glucose. Forty islets were then incubated in the presence of 10 mM LiCl, 1 mM inositol and 10 mM glucose with or without the anomers of PNP-Glu. [3H] radioactivity in the incubation medium remained significantly greater in the presence of the alpha-anomer of PNP-Glu than in the presence of glucose alone after 5- and 20-min incubation. The inositol monophosphate levels in the islets incubated with glucose alone were increased more than in the islets with alpha-anomer. The beta-anomer of PNP-Glu did not change either glucose-induced insulin release or phosphoinositide breakdown. A patch-clamp study revealed that neither anomer affected the glucose-dependent ATP-sensitive K(+)-channels. These results indicate that the anomeric preference for glucose in insulin release in the pancreatic islets is closely associated with phosphoinositide breakdown.

Effects of transection of the greater superficial petrosal and te chorda tympani nerves on conditioned taste aversion to sucrose in the hamster.

For a further understanding of the gustatory function of the greater superficial petrosal nerve (GSP), effects of bilateral sectioning of the GSP and/or the chorda tympani nerves (CT) in hamsters on discriminating sucrose taste were examined through conditioned taste aversion paradigm. Licking pattern was monitored in experimental and sham control male hamsters. Once the animal was conditioned to avoid 0.1 M sucrose solution by i.p. injection of 0.5 M LiCl, the animal avoided to lick sucrose solution at higher concentration above 0.01 M. The degree of the aversion was significantly decreased when the GSP and/or the CT were sectioned bilaterally. The order of the sectioning effects was GSP+CT>GSP≥CT>sham. These results suggest that the GSP plays an important role for mediating sweet taste information, which is consistent with neurophysiological data in the hamster.

Electrophysiological and behavioral studies on the taste of umami substances in the rat

Electrophysiological and behavioral experiments were performed to reveal taste properties of “umami” substances such as monosodium glutamate (MSG) and disodium inosine monophosphate (IMP) in rats. To eliminate the taste effects of Na ions contained in these umami substances, we dissolved them in 0.01 mM amiloride, which is known to block sodium responses. In the electrophysiological study, taste responses of the whole chorda tympani nerve were recorded. The magnitude of responses to MSG (or IMP) at concentrations below 0.1 M (or 0.01 M) was less than 10% of that to 0.1 M NaCl. On the other hand, the mixtures of MSG and IMP showed responses 2–7 times larger than the arithmetric sum of the responses to each component of the mixtures. A new sweet taste inhibitor ( Gymnema sylvestre extract) strongly suppressed neural responses to mixtures of MSG and IMP as well as sucrose, but only weakly or negligibly to individual solutions of these umami substances. In the behavioral study, the brief exposure two-bottle preference test and conditioned taste aversion paradigm were used. MSG was most preferred at 0.3 M (preference ratio = 57%), IMP, at 0.01 M (61%), and both were less preferred or rejected at higher concentrations. In contrast, mixtures of MSG and IMP were more preferred at a broad concentration range (e.g., 82% for 0.1 M MSG + 0.01 M IMP). Aversive conditioning to umami substances was generalized to sucrose, and vice versa, but not to 0.1 M NaCl, 0.01 M HCl, and 0.1 mM quinine hydrochloride. In conclusion, taste responses of umami substances without participation of Na ions can be evoked in rats at relatively high concentrations and by dissolving them in amiloride solution. The taste of umami substances is very similar to the taste of sucrose. A possibility is discussed that the individual solutions of MSG and IMP may be different from the mixtures of these substances in terms of transduction mechanism.