The ontogeny of feeding in rats: II. Independent ingestive behavior.

In 4 experiments, Charles River rat pups 3 days of age and older consumed large quantities of milk, sucrose, and wet mash when the Ss were placed in warm containers in which one of these diets had been spread on the floor. The volume of Ss" intake was directly related to the severity of food deprivation. Ingestive behavior occurred in the early part of the 30-min test, but later in the test, Ss stopped feeding and became quiescent. Their ingestive behavior thus resembled that of adults in (a) the motor aspects of feeding responses (licking and lapping), (b) the dependency on deprivation for intake, and (c) the pattern of intake termination. However, in Exp IV, when diet was restricted to a small area of the test container, young Ss consumed little diet. They did not appear able to direct or focus their ingestive responding. It was not until 9–12 days of age that Ss successfully consumed milk from a localized source. (29 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Septal lesions and behavior: Effects of presurgical rearing and strain of mouse.

In 2 experiments a total of 64 black C57BL/10J and 64 albino SJL/J male mice were reared in either enriched social cages or restricted individual cages from 25 days of age until they underwent septal or control surgery 1 mo later. Enrichment differentially altered septal or control behavior as measured by fluid consumption of water, saccharin, and quinine; performance on a rotorod; and the acquisition of an active avoidance task. The interactions of presurgical history with brain damage were manifested differently in the 2 strains of mice. The importance of attending more to genetic and presurgical history in attempts to define the effects of brain damage on behavior and to determine the function of brain structures is discussed. (25 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Gustatory parabrachial lesions disrupt taste-guided quinine responsiveness in rats.

This study examined the effects of electrophysiologically placed electrolytic lesions in the gustatory zone of the parabrachial nuclei (PBN) on the rat's taste-guided unconditioned licking of quinine hydrochloride during repeated 10-sec trials. Concentration–response functions measured in water-deprived rats before and after surgery significantly shifted to the right as a result of the bilaterally placed lesions. These same rats were tested on their ability to acquire a lithium chloride (LiCl)-based conditioned taste aversion (CTA) to 0.1 M sucrose. Although the largest lesions severely affected performance in both tasks, there was only a modest correlation (r?=?–.447) between the extent of the lesion-induced shift in the quinine concentration–response curves and the degree of sucrose intake suppression after the first CTA conditioning trial. Thus, PBN lesions can disrupt performance on both tasks, but it appears that the neural processes governing unconditioned responsiveness to quinine may be to some extent dissociable from those subserving acquisition of a sucrose–LiCl-based CTA. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Genetic versus hypothalamic obesity: Studies of intake and dietary manipulations in rats.

Studied feeding behavior in 4 experiments with a total of 86 Zucker rats. Ad-lib food and water intakes were significantly greater for the genetically obese rats (fatties) than for their nonobese littermates. The ratio of water intake per gram of food intake was not different for the 2 groups. The ability to regulate caloric intake was then tested in 4 groups of rats: genetically obese, ventromedial hypothalamic lesioned (VMH) obese, sham operated, and normal controls. In response to caloric dilution and quinine adulteration the genetically obese Ss behaved more like normal Ss than like VMH-lesioned Ss. Sensitivity to quinine increased with age in the Zucker fatty. The fact that Ss with genetic obesity and Ss with hypothalamic obesity displayed different behaviors suggests that obesity is not merely a unitary disorder. (20 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Intraoral intake and taste reactivity responses elicited by sucrose and sodium chloride in chronic decerebrate rats.

Oral stimulating effects of sucrose and NaCl were assessed in chronic decerebrate and pair-fed intact control rats by measuring oral motor taste-reactivity responses (TRRs) and intraoral intake (II) volume. TRRs were videotaped during the 1st minute of the intraoral taste infusion. The infusion continued until the taste solution was rejected from the mouth, and the intake volume was computed accordingly. The number of ingestive TRRs and the volume of II consumed by pair-fed control and decerebrate rats increased with increasing sucrose concentration. Sucrose intake increased as concentration increased, then plateaued for both groups. For controls, intraoral NaCl elicited an inverted U-shaped function for both TRRs and intake. TRRs of chronic decerebrate rats varied with NaCl concentration. In contrast with controls, intake of NaCl did not differ from that of water for decerebrate rats. Data indicate that caudal brain-stem mechanisms are sufficient to control sucrose intake but not adequate for the concentration dependent intake of NaCl. Data indicate it is possible for taste-elicited oral motor responses to be dissociated from intake. Roles of taste and postingestive factors in sucrose and NaCl intake are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Taste response to mixtures: Analytic processing of quality.

The tastes of 100 mM sodium chloride (NaCl), 100 mM sucrose, and 1 mM quinine hydrochloride in mixtures were investigated in golden hamsters (Mesocricetus auratus) with a conditioned taste aversion (CTA) paradigm. CTAs, established in golden hamsters by injection of lithium chloride, were quantified as percent suppression of control 1-hr stimulus intake. CTAs for 10 of 15 stimulus pairs with common components symmetrically cross-generalized, suggesting that component qualities were recognized in binary and ternary mixtures. However, CTAs to quinine were hardly learned and were weakly expressed when quinine was mixed with NaCl, and generalizations from multiple to single stimuli were stronger than vice versa (i.e., asymmetric). The behaviors reflect peripheral inhibition and/or central mixture suppression. Nonetheless, components retain their distinct qualities in mixtures, suggesting that taste processing is analytic. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Ontogeny of thirst in the rat: Effects of hypertonic saline, polyethylene glycol, and vena cava ligation.

Describes 3 experiments in which over 465 Sprague-Dawley rats of various ages either (a) were injected with hypertonic sodium chloride solutions to produce intracellular dehydration, (b) were injected with polyethylene glycol to induce hypovolemia, or (c) underwent ligation of the inferior vena cava to stimulate the renin-angiotensin system. 16-day-old Ss drank like adults after injection of polyethylene glycol. Hypertonic saline injection did not elicit adultlike drinking until 30 days of age, and vena cava ligation did not produce adult levels of water consumption until 42 days postnatally. It is concluded that treatments which have been associated with different mechanisms of thirst, therefore, first become effective at different times during ontogeny. (27 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Ontogeny of meal patterning in rats and its recapitulation during recovery from lateral hypothalamic lesions.

Investigated the development of feeding patterns in weanling rats and in rats with lateral hypothalamic lesions. 2 experiments were conducted with a total of 39 male albino Sprague-Dawley rats. From 16 to 25 days of age, the weanlings demonstrated a preprandial intake pattern (i.e., a positive correlation between meal size and time since the preceding meal). This subsequently declined while the postprandial relationship (correlation with time until subsequent meal) such that by 30-35 days of age a full adult pattern was observed. Ss recovering from lateral hypothalamic lesions, for a brief period, also demonstrated a preprandial intake pattern. The postprandial relationship was abolished by the lesion. Results suggest that the development of adult meal patterning results from maturation of lateral hypothalamic mechanisms governing meal initiation. (40 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Response latency of gerbils and hamsters to nuts flavoured with bitter-tasting substances

The unconditioned reactions of Mongolian gerbils to peanuts rolled in sucrose octa-acetate (SOA) or denatomium benzoate (Bitrex) were studied in Experiment 1. Although SOA evokes as high a bitterness rating among humans as quinine salts, the gerbils' latency to ingest a nut flavoured with the former was similar to that to an unflavoured nut. Their oral latency to a nut that was flavoured with Bitrex was longer than to either an unflavoured one or one flavoured with SOA. However, the fact that they ingested a nut flavoured with the "most bitter substance known to man" within 70 sec after contact is surprising. Experiment 2 dealt with the effects of a peanut that was either unflavoured or flavoured with SOA or quinine and then paired with a LiCl injection. The oral latency of these gerbils to a nut conveying such flavours was assessed for six days after this conditioning. A nut flavoured with quinine acquired aversive properties but not ones that were flavoured with SOA or were unflavoured. Similar results were observed in Experiment 3, when hamsters were tested under comparable conditions. The theoretical implications of these results are discussed.     

Ontogeny of meal patterns of the rat.

Two experiments, one with 6 18-60 day old female Wistar rats and the other with 12 Wistar and Long-Evans rats, examined the development of adult rat meal patterns. Although diurnal differences in food intake were present as early as 18 days after birth, with significantly more food being consumed in the dark, these differences were much smaller than those seen in adults. Nocturnal feeding gradually increased, reaching adult levels at around 6 wks of age. In general, little or no direct correlation was observed between meal size and postmeal interval length until rats were 4-5 wks old. Thereafter, correlations of +.40 or higher were usually observed. On the other hand, correlations averaging around zero were observed between meal size and premeal interval at all ages studied. Results are discussed in terms of their implications for proposed physiological mechanisms determining meal onset. (25 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Ingestive responses of human newborns to salty, sour, and bitter stimuli.

In 2 experiments a total of 204 16-90 hr old neonates were offered 2 fluids differing in taste for 3 min each. The volumes ingested were measured. Ss offered water and bitter and sour solutions did not ingest them differentially, which corroborated earlier observations with weaker solutions. A sucrose solution was used to raise baseline ingestion above that of water. Ss offered the sucrose solution with and without urea, citric acid, or sodium chloride consumed less of it when citric acid was added. They were indifferent to the addition of urea or sodium chloride. The failure to observe intakes lower than that of water suggests that newborns maximally inhibit their ingestion of water. The effect of sex, age, birth weight, and individual consistency on intake were assessed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Temporal and Qualitative Dynamics of Conditioned Taste Aversion Processing: Combined Generalization Testing and Licking Microstructure Analysis.

The pattern of licking microstructure during various phases of a conditioned taste aversion (CTA) was evaluated. In Experiment 1, rats ingested lithium chloride (LiCl) for 3 trials and were then offered sodium chloride (NaCl) or sucrose on 3 trials. A CTA to LiCl developed and generalized to NaCl but not to sucrose. CTA intake suppression was characterized by reductions in burst size, average ingestion rate, and intraburst lick rate, and increases in brief pauses and burst counts. Compared with previous studies, LiCl licking shifted from a pattern initially matching that for normally accepted NaCl to one matching licking for normally avoided quinine hydrochloride by the end of the 1st acquisition trial. In Experiment 2, a novel paradigm was developed to show that rats expressed CTA generalization within 9 min of their first LiCl access. These results suggest that licking microstructure analysis can be used to assay changes in hedonic evaluation caused by treatments that produce aversive states. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Stimulus preexposure reduces generalization of conditioned taste aversions between alcohol and non-alcohol flavors in infant rats.

Results of 3 experiments showed that infant rats (age 13-17 days) generalize conditioned taste aversions between alcohol and non-alcohol tastes such as a mixture of sucrose and quinine, apple cider vinegar, or coffee. Nonreinforced preexposure to those tastes reduced generalized aversions between them. Generalization between alcohol and sucrose-quinine was reduced not only after preexposure to both tastes, but also when only the nonconditioned taste was preexposed, whereas with alcohol and vinegar, both tastes had to be preexposed to obtain that effect. In no case was generalization reduced when only the to-be-conditioned taste was preexposed. Previous experience with alcohol alone, as well as with similar gustatory stimuli, may enhance subjects' ability to differentiate them during infantile stages in rats. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Hyperactivity to quinine associated with osmotic thirst in the rat.

Studied cellular and extracellular fluid depletion in 5 experiments with Sherman female albino rats (N = 103). Drinking in response to cellular dehydration, but not in response to water deprivation, was severely disrupted by mild quinine adulteration of the drinking fluid. Cellular dehydration in conjunction with deprivation, although enhancing the intake of water, actually suppressed quinine intake. In contrast, intravascular fluid depletion added to water privation enhanced intake both of water and of quinine solutions. It is concluded that the heightened reactivity to quinine which accompanies cellular dehydration reflects a specific property of the osmotic-thirst mechanism. (24 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Reactivity of normal and VMH-lesion rats to quinine-adulterated foods: Negative evidence for negative finickiness.

Conducted 2 experiments with ventromedial hypothalamic (VMH) and normal rats to examine (1) whether the anorexic properties of quinine depend on quinine's sensory properties or on its postingestive effects, and (2) whether VMH rats overrespond to quinine adulteration. These issues were examined by comparing the feeding adjustments to quinine by VMH and normal male Long-Evans rats in a sham-feeding situation and under normal feeding circumstances, on Ss' initial exposure to this drug. In Exp I, 17 Ss received VMH lesions or sham lesions before being sham fed with various concentrations of quinine. In Exp II, 18 lesioned or sham-lesioned Ss were fed unadulterated food for 12 days, followed by a meal adulterated with quinine, 2 days of pure mash, and 1 day of quinine. Quinine caused significant depression of food intake in Ss. Little evidence exists for a conclusion that VMH rats are more reactive than normals to quinine-adulterated foods. Results suggest that major food intake perturbations of VMH rats are in response to hedonically positive dietary manipulations. (31 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Control of fluid palatability by exteroceptive Pavlovian signals.

Two experiments, with 15 male albino rats, investigated whether discrete auditory conditioned stimulus/stimuli (CS) that signal the availability or onset of taste unconditioned stimulus/stimuli (UCS) (sucrose, quinine) can control orofacial responses in the absence of those UCSs. In Exp I, one auditory stimulus (CS+) was paired with the delivery of a sucrose solution to the magazine floor, and another auditory stimulus (CS–) was never followed by sucrose. Following conditioning, oral infusions of water that were preceded by the CS+ were found to elicit more ingestive (sucrose-typical) orofacial responses than did water alone or water preceded by the CS–. In Exp II, the conditioned ingestive reactions to a signal for sucrose observed in Exp I again occurred, and conditioned aversive (quinine-typical) orofacial responses occurred in response to water infusions preceded by a former signal for quinine. Data suggest that perceived palatability may be influenced by Pavlovian associations involving exteroceptive CSs and illustrate the importance of supporting stimuli in modulating the effects of Pavlovian associations on behavior. (41 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Acamprosate and alcohol: I. Effects on alcohol intake following alcohol deprivation in the rat

Acamprosate (calcium-acetyl homotaurinate) is a new compound in the treatment of alcoholism. Its efficacy has been proven in several clinical trials and registration is now pending in most European countries. The basic mechanisms by which acamprosate elicits its anti-craving action, thereby leading to reduced relapse rates, is not known at the moment. In the present study we describe a rat model of long-term alcohol-drinking which mimics relapse behavior in human alcoholics. The effect of acamprosate was studied in this model. Wistar rats had a free choice between water and alcohol solutions of different concentrations (5, 10, 20% v/v). After two months of continuous alcohol access, rats were deprived of alcohol for three days. Following this deprivation phase, all alcohol solutions were presented again. This procedure was repeated monthly for the following six months. The rats consumed 3.5 +/- 0.3 g/kg alcohol a day. After alcohol deprivation, alcohol intake rose to 5.2 +/- 0.3 g/kg per day resulting in blood alcohol levels of 30 +/- 6 mg/dl. Interestingly, the addition of quinine to the alcohol solutions or the additional presentation of a 5% sucrose solution did not affect the alcohol-deprivation effect after eight months of this intermittent alcohol exposure. However, when acamprosate (50-200 mg/kg i.p.) was administered twice daily, alcohol-drinking following an alcohol-deprivation phase was decreased dose dependently. Given at the highest dose alcohol intake even dropped significantly below baseline drinking. Together, these results show that acamprosate effectively diminishes the alcohol-deprivation effect. Furthermore, the described model seems to be a suitable animal model to screen compounds for their anti-relapse properties and subsequently for their anti-craving action.     

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.     

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)     

Stress and consumption: Inescapable shock, neophobia, and quinine finickiness in rats.

Exposure to inescapable shock has been shown to result in reduced consumption of quinine in water (the finickiness effect) in rats. In the present experiment, (1) a clear difference in finickiness occurred between male adult rats exposed to inescapable shock and those exposed to escapable shock (the first such demonstration), (2) finickiness was reinstated 20 days later, and (3) finickiness was eliminated by quinine exposure prior to treatment. The 1st 2 results support the role of uncontrollability and/or unpredictability in finickiness and extend its potential impact to long-term consequences. This allows greater potential for the modeling of long-term effects, such as eating disorders and depression in humans. The finding that preexposure to quinine eliminated finickiness is contrary to current accounts of the effect. Accounts of finickiness are proposed in terms of classically conditioned aversions, bitterness, and neuropeptide control of ingestion. (PsycINFO Database Record (c) 2010 APA, all rights reserved)