Effects of dietary NaCl deprivation during early development on behavioral and neurophysiological taste responses.

Investigated whether the gustatory system can be modified by restricting dietary NaCl during early development by recording neurophysiological taste responses in Sprague-Dawley rats at various times after deprivation (Exp I), and by measuring behavioral taste preferences in 3 groups of 7 NaCl deprived adult rats (Exp II). Overall findings indicate that Ss deprived of dietary NaCl from the 3rd day of gestation to 12 days postnatally and then placed on a NaCl-replete diet had chorda tympani nerve responses similar to those of nondeprived Ss when recordings were made at 28 days of age and older; however, preferences for NaCl solutions over water were significantly less than those of controls when tested at adulthood. NaCl deprivation in Ss from the 3rd day of gestation to approximately 35 days postnatally resulted in altered chorda tympani nerve responses to NaCl but not to other stimuli such as NH?Cl and KCl. Thus, it is concluded that restriction of dietary NaCl at a period in the rat's development when peripheral and central taste responses are changing results in short-term alterations in peripheral neural responses and in long-term changes in preference behaviors. (36 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Sex differences in electrophysiological and behavioral responses to NaCl taste.

We tested the hypothesis that sex differences in preference for NaCl are attributable to estrogen-mediated alterations in gustatory processing. Electrophysiological responses of the chorda tympani nerve to NaCl were blunted by estrogen treatment in ovariectomized female rats, suggesting that females are less sensitive to concentrated NaCl solutions during high estrogen conditions. In contrast, after a taste aversion was conditioned to 150-mM NaCl, estrogen- and oil-treated ovariectomized rats generalized the aversion to a lower concentration of NaCl than did males, suggesting that females are more sensitive to the taste of dilute NaCl solutions regardless of estrogen. Thus, sex differences in NaCl preferences may be attributable to differences in NaCl taste processing that involve both acute and developmental effects of estrogen. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Relative taste thresholds for ethanol, saccharin, and quinine solutions in three strains of rats nonselected for ethanol: A comparative study.

C. P. Richter and K. H. Campbell (1940b) originally defined taste threshold as "the point at which the rats first indicated that they recognized a difference between the distilled water and the solutions" (p. 34). The present study sought to apply this simple behavioral measure to the investigation of strain differences in taste sensitivities, particularly with respect to predictive relationships in ethanol, saccharin, and quinine preference. Fawn-Hooded, Lewis, and Wistar rats were presented with gradual increments in concentration of ethanol (0.01-15%; C. P. Richter & K. H. Campbell, 1940a), saccharin (0.002-3%) or quinine (0.000 1-0.0055). Results showed that although intake for saccharin was similar in all strains, consumption of ethanol and quinine differed among the groups. Although previous research has proposed that sweet preference is a promising behavioral marker for ethanol preference, these results suggested that bitter preference may be a more reliable predictor of ethanol preference in rats. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Perceptual characteristics of the amiloride-suppressed sodium chloride taste response in the rat.

Assessed the contribution of amiloride-sensitive membrane components to the perception of NaCl taste using a conditioned taste aversion procedure with 8 groups of adult rats conditioned to avoid either 0.1M NaCl, 0.5M NaCl, 0.1M NH?Cl, or 1.0M sucrose while their tongues were exposed either to water or to amiloride hydrochloride. Differences in the acquisition of taste aversions between the amiloride- and nonamiloride-treated groups were not apparent when the conditioned stimulus (CS) was 0.5M NaCl, 0.1M NH?Cl, or 1.0M sucrose. Although the magnitude of the 0.5M NaCl aversion was similar between amiloride- and nonamiloride-treated Ss, the perceptual characteristics of the CS differed between groups. Amiloride-treated Ss avoided monochloride salts after conditioning to 0.5M NaCl but not nonsodium salts or nonsalt stimuli. Ss not treated with amiloride only generalized the 0.5M NaCl aversion to sodium salts. The "salty" taste of NaCl is related to the amiloride-sensitive portion of the functional taste response in rats. The portion of the NaCl response insensitive to amiloride has "sour-salty" perceptual characteristics and is not perceived as being salty. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Amiloride-insensitive units of the chorda tympani nerve are necessary for normal ammonium chloride detectability in the rat.

In spite of its common use as a standard stimulus in peripheral nerve recordings, relatively little is known about the psychophysics of NH?Cl taste. Rats' detection threshold for this salt was tested under a variety of conditions, including amiloride (100 μM) treatment and bilateral chorda tympani (CT) nerve transection. Detectability was measured with a 2-lever operant discrimination procedure used previously to measure detection thresholds for NaCl and KCl. Although NH?Cl and KCl appear to share a common taste quality and transduction mechanism, the logistic function and threshold for NH?Cl were found to be more similar to those of NaCl than to those of KCl. Like that of KCl, however, the detection threshold for NH4Cl increased significantly with CT transection (0.54 log?? units, p     

Amiloride sensitivity in the neonatal rat.

Amiloride-sensitive sodium (Na) channels in taste buds appear to play a key role in the response to NaCl stimulation, at least in adult rats. The researchers examined whether neonatal rats, which display an exaggerated preference for hypertonic NaCl solutions, lack functional amiloride-sensitive Na channels. NaCl intake was significantly reduced by amiloride pretreatment, but water and ammonium chloride were unaffected. The researchers assessed whether the early appearance of amiloride sensitivity was mediated by effects on chorda tympani (CHT) activity by sectioning the CHT before testing. CHT transection reduced intake of NaCl solutions and eliminated evidence of amiloride sensitivity. Amiloride sensitivity was also assessed by recording of whole-nerve CHT activity at 8 to 11 days of age; the response to NaCl stimulation was significantly suppressed by amiloride. These data indicate that amiloride-sensitive Na channels develop earlier than previously believed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of lesions of the gustatory neocortex on taste aversion learning in the rat.

In 5 experiments, 110 normal male Long-Evans hooded rats and 125 Ss with lesions of the gustatory neocortex (GN) were compared for their ability to learn aversions to taste cues paired with toxicosis. When the taste presentation was followed immediately by toxicosis, normal Ss and 8 Ss with lesions of the posterior (visual) neocortex learned aversions to sucrose, sodium chloride, quinine hydrochloride, and hydrochloric acid solutions. Ss with GN lesions learned aversions to all solutions except sucrose. In preference tests, all solutions were shown to be discriminable from water by both normal and GN-lesioned Ss. Under conditions in which a 6-hr delay separated taste presentation and toxicosis, normals again learned specific aversions to all 4 solutions, but Ss with GN lesions failed to learn specific aversions to sucrose, sodium chloride, and hydrochloric acid solutions. It was shown that the ability of Ss with GN lesions to learn aversions to sucrose and quinine depended on stimulus concentration. It is proposed that the data can be accounted for by postulating a change in the threshold for taste illness associations following GN lesions. (30 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Do taste factors contribute to the mediation of ethanol intake? Ethanol and saccharin-quinine intake in three rat strains

Several recent studies have suggested that ethanol-preferring rodents may also have an affinity for sweet solutions (saccharin, sucrose) and, conversely, that saccharin preference may predict ethanol preference. The purpose of the present investigation was to determine whether intake of ethanol and saccharin-quinine (SQ) solutions would be related in three nonselected strains of rats who differ in their ethanol preference: Lewis, Wistar Kyoto, and Wistar. In the first phase of the experiment, all animals were presented with an ascending series of ethanol solutions (2 to 10%) in free choice with water, followed by a 10-day maintenance period of 10% ethanol with water. In the second phase, the same animals were presented with an ascending series of SQ solutions (saccharin: 0.4%, quinine: 0.001 to 0.04%) in free choice with water, followed by a 10-day maintenance period of 0.4% saccharin with 0.04% quinine and water. The results revealed an absence of a direct relationship between ethanol and SQ consumption. The ethanol-nonpreferring Lewis rats showed a greater preference for the SQ solutions than Wistar Kyoto rats, whereas the ethanol-preferring Wistar Kyoto strain consistently consumed significantly less SQ. Wistar rats showed relatively stable consumption levels for both solutions that fell between those of the other two strains. These results suggested that the relationship between ethanol and SQ preference in rats was not a direct one and did not support the findings in the literature of a simple overall positive relationship between sweet and ethanol preference. These data do, however, provide further evidence for taste factors in the mediation of self-selection of ethanol in rats.     

Rats learn to like the taste of morphine.

When rats are forced to drink a morphine solution as their only source of fluid, they eventually reverse their initial preference and drink more morphine than water in a 2-bottle preference test. Two experiments with 13 male Holtzman rats examined the cause of this shift in preference using the taste reactivity test, which involves the analysis of fixed action patterns elicited by taste solutions infused into Ss' mouths. Three morphine concentrations (0.03, 0.6, and 1.5 mg/ml) and 2 levels of motivation (drug-replete and drug-withdrawal states) were studied. A greater percentage of ingestive taste reactivity responses occurred to the oral morphine infusion in morphine-raised than in water-raised Ss. Data are inconsistent with the idea that enhanced morphine ingestion is caused by anticipation of positive consequences. Instead, they support the idea that rats come to "like" the flavor of the morphine solution; in other words, the palatability evaluation of the morphine changes, possibly through an association between the flavor and the hedonically positive effects of the morphine. (33 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Negative anticipatory contrast and preference conditioning: Flavor cues support preference conditioning, and environmental cues support contrast.

In 2 experiments, access to a .15% saccharin solution was followed on alternating days by access to a 32% sucrose solution and the same saccharin solution. In Exp 1, rats increased both intake of and preference for a flavored saccharin solution that predicted sucrose, but neither effect was found using a predictive odor cue alone. Exp 2 replicated the predictive flavor results but showed suppression of saccharin intake when environmental cues predicted sucrose. When both flavor and environment predicted sucrose, saccharin intake did not change, but preference for the predictive flavor increased. Discriminative taste cues appear to facilitate the development of preference conditioning, but environmental cues favor negative anticipatory contrast effects. Also, preference conditioning and contrast may develop concurrently and compete for expression. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A study on the relationship between antisense EGFR cDNA fragments and nuclear matrix proteins in glioblastoma cells

The effects of physical exercise on preference for various sapid solutions was studied in 58 healthy university students. After 30 min of exercise using a bicycle ergometer at 50% VO2max (maximal oxygen uptake) intensity, a rating scale test on taste hedonic tone and the triangle test for taste absolute threshold were done. The test solutions were sucrose, NaCl, citric acid, caffeine and monosodium glutamate (MSG). Preference scale values for sucrose and citric acid increased after exercise, whereas the values for NaCl, caffeine and MSG were not changed. The absolute thresholds for all the sapid solutions did not differ for pre- and post-exercise. These findings indicate that in humans preference for sucrose and citric acid increase after physical exercise.     

Chorda tympani nerve transection, but not amiloride, increases the KCl taste detection threshold in rats.

Water-restricted rats were trained to press one lever after KCl presentation and the other lever after distilled water. Water reinforcement was given after each correct response, and a time-out followed each incorrect response. Rats were trained and tested on KCl stimuli of varying concentrations. Threshold was defined as the KCl concentration corresponding to ? the maximum asymptote of performance for each rat. The geometric mean KCl detection threshold for all rats was 0.033 M KCl. Rats that had the chorda tympani nerve (ChT) bilaterally transected showed an average increase in KCl threshold of approximately 0.60 log?? units, whereas sham-operated rats showed no change. Control rats retested with 100 μM amiloride added to all KCl concentrations and water displayed no change in threshold. These results suggest that although the ChT contributes significantly to the rat's sensitivity to KCl, amiloride-sensitive taste transduction pathways do not. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Neonatal ablations of the gustatory neocortex in the rat: Taste aversion learning and taste reactivity.

Sprague-Dawley rats sustaining ablations of gustatory neocortex (GN) at 2, 10, 20, or 60 days of age were compared with control-lesion and anesthetized controls (N?=?151) in the acquisition and extinction of a learned taste aversion. Ss were also tested for taste preference across 5 concentrations of NaCl solution (.04, .08, .15, .3, and .6 M). Results indicate that GN ablation disrupted aversion acquisition and extinction regardless of age at surgery. Taste-response functions for solutions shown by all GN Ss mirrored those of controls: preference (relative to water baseline) for middle concentrations and rejection of the strongest concentration. It is suggested that the 20- and 60-day-old GN Ss were hyperresponsive to the suprathreshold concentrations of NaCl (excepting the .6-M concentration). The increased response to NaCl in 20- and 60-day-old GN Ss may have been related to the significant decreases in water consumption relative to that of controls. Water consumption of controls and GN Ss in 2- and 10-day-olds was essentially equal. It is concluded that infant ablation of the GN does not spare normal taste aversion learning and that rats with GN ablations, regardless of age at surgery, respond in a normal manner to the hedonic aspects of NaCl solutions. (22 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

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 ? of the rats did not perform competently, ? had elevated thresholds, and ? 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. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Sodium depletion enhances salt palatability in rats.

Stereotyped fixed action patterns (FAPs) elicited in rats by oral infusions of taste solutions can be classified as either ingestive or aversive. They reflect the palatability of the taste and can be modified by learning and by the physiological state of the animal. The present 2 experiments, with 5 male Sprague-Dawley rats, demonstrated that when the physiological state of the S was altered by sodium depletion, the pattern of FAPs elicited by oral infusions of 0.5 M NaCl shifted from a mixture of ingestive and aversive components (while sodium replete) to exclusively ingestive ones (while sodium deplete). This shift in taste reactivity occurred the 1st time the Ss were made sodium deplete. A similar shift did not accompany infusions of 0.01 M HCl, a taste solution that also elicited mixed ingestive and aversive FAPs. This result suggests that the shift in response to NaCl was not due to a general change in ingestive bias or to a general taste deficit. On the basis of the change in FAPs, it is concluded that the palatability of highly concentrated salt solutions increases in sodium-deplete rats. Such a shift in salt palatability may be instrumental in directing the appetitive behavior of the animal. (33 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Hormonal regulation of adult partner perference behavior in neonatally ATD-treated male rats.

Male rats, neonatally treated with ATD (1,4,6-androstatriene-3,17-dione), which blocks the aromatization of testosterone into estradiol (E?), were tested for adult partner preference behavior (PPB; estrous female vs active male). Castration caused a decrease in preference for the female partner in all males, with ATD males showing lower preference for the female partner than controls. Long-term castrated males did not show preference for either partner. Precastration levels of PPB in control males occurred after treatment with E? or dihydrotestosterone (DHT) plus E?. DHT alone had no effect on PPB. With E? alone, the ATD males clearly preferred the male partner. When DHT was added, these ATD males showed no preference for either partner or a low preference for the female partner. In conclusion, adult PPB in male rats is activated by endogenous testosterone or by both its metabolites (DHT and E?) or by E? alone. ATD males showed a much lower preference for the female. There was a differential effect of DHT and E?: DHT had no effect, but E? clearly caused ATD to prefer the male partner and control males to prefer the female partner. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Amiloride increases sodium chloride taste detection threshold in rats.

The epithelial sodium-channel blocker amiloride has been shown to inhibit sodium responses in the 7th cranial nerve of the rat. In the signal detection task used in this study, amiloride (100 μM) treatment raised the NaCl threshold by ～1 log?? unit. The inhibition constant for amiloride was 1μM at 0.013 M NaCl. Because the NaCl intake of adult rats has been shown to be related to the level of dietary NaCl exposure early in development, rats were exposed by way of maternal diet to 1 of 3 diets (0.1% NaCl, n?=?8; 1.0% NaCl, n?=?8; 3.0% NaCl, n?=?9) from conception through weaning, to determine whether this treatment affects taste sensitivity. At Postnatal Day 30, rats were placed on 1.0% NaCl chow. This treatment did not affect NaCl detection or amiloride sensitivity in adulthood. The amiloride-induced shifts in NaCl sensitivity functions imply that the transcellular sodium transduction pathway is necessary for normal NaCl detection in the rat. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Swelling of collagen fibers in neutral salt solutions (author's transl)

When applying various concentrations of NaC104 (0.15-7 M) to tendon fibres from rat tails, we found denaturation beginning at 2M, and with increasing concentration a linear increase of the maximal contraction tension and an expoential shortening of the contraction time down to a minimal value of 7.5 min. In a second group of experiments we investigated the weight changes of tendons of old (26-30 months) and young (8 months) rats treated with 5M NaC104 and compared the weight curves and the tension curves. We found an increase in weight up to 900% as the tension decreased. This indicates a connection between the swelling and the relaxation of collagen fibres. Other solutions of neutral salts (5M NaC103, NaC1; 0.15 M NaC104, NaC103, NaC1) tested on young and old tendons did not produce any tension nor other visible changes. The weight curves show an immediate increase up to about 200% which remains constant and which is low compaired with the effect of 5M NaC104. The reason for the contraction of tendon fivres seems to be the denaturation caused by the increased lipophilia of the aqueous salt solutions, while the relaxation is merely the result of the subsequent swelling of the collagen fibre.     

Ibotenate lesions of the hippocampus enhance latent inhibition in conditioned taste aversion and increase resistance to extinction in conditioned taste preference.

In 2 experiments, the effects of axon-sparing lesions of the hippocampus on performance in aversive and appetitive taste conditioning tasks were investigated. In Exp 1, hippocampally lesioned rats showed no impairment of conditioned taste aversion learning relative to controls, but they did display an increased sensitivity to latent inhibition (LI). In Exp 2, the same hippocampectomized rats acquired a conditioned taste preference but failed to show any evidence of extinction. The influence of the neurotoxic lesion on LI is in the opposite direction to the effect typically found following hippocampal damage induced by traditional methods. Accordingly, the data present challenges for most current theories of hippocampal function. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Conditioned place preference for mating is preserved in rats with pelvic nerve transection.

Female rats exhibit a conditioned place preference (CPP) for a context paired with mating. The present experiment tested the hypothesis that the activation of the pelvic nerve mediates the reinforcing effects of mating for female rats. Rats underwent bilateral pelvic nerve or sham transection and then received paced mating, nonpaced mating, or the control treatment during a CPP procedure. Pelvic nerve transection did not affect the CPP for paced or nonpaced mating. In tests of paced mating behavior, contact-return latencies following intromissions were significantly shorter in rats with pelvic nerve transection than they were in rats with sham transections. These results show that the pathway conveying the reinforcing effects of mating stimulation does not depend on the integrity of the pelvic nerve, but that activation of the pelvic nerve contributes to the display of paced mating behavior. (PsycINFO Database Record (c) 2010 APA, all rights reserved)