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)     

The ontogeny of feeding in rats: V. Influence of texture, home odor, and sibling presence on ingestive behavior.

Determined with Charles River rat pups in 3 experiments that terry-cloth texture, home odor, and the presence of siblings modulated Ss' ingestive behavior. Unlike warmth, which affected ingestion in pups until at least 15 days of age, the relative importance of other cues varied with age. At 3 days, ingestion was dependent on warmth but was not influenced by the other cues. At 6 days, texture and home odor enhanced ingestive behavior (intake, activity, mouthing, and probing), but the presence of siblings had no effect. Home odor or terry-cloth texture did not alter the ingestive behavior of 12-day-olds, but the presence of siblings enhanced milk intake. Thus, during development, the external sensory controls for ingestion became progressively more complex. Warmth served as a primary permissive cue for ingestion, but as Ss grew older, such other cues as odor, texture, or social stimuli also gained significance. (33 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Sensitization of ingestive responding in preweanling rats: Time course and specificity.

Two experiments measured the response-enhancing effects of oral stimulation in young rats with no feeding experience. In Experiment 1, pups were implanted with oral cannulas and deprived for 0, 6, or 24 hr. In nondeprived rats, sucrose exposure transiently sensitized oral responding to subsequent stimuli for several minutes. Among 24-hr-deprived rats, baseline oral responding had increased to where sucrose exposure was no longer sensitizing. Unlike oral responding, sensitization of activity by sucrose exposure increased with deprivation. Sensitization was also evident in the microstructure of responses to infusions. In Experiment 2, the specificity of sensitization was examined by varying stimulus palatability. Sucrose exposure sensitized oral responding to both sucrose and quinine-adulterated sucrose, but quinine-adulterated sucrose was not sensitizing. The results suggest that in inexperienced rats, oral stimulation initiates changes in responding that may mimic the endogenous sequelae of deprivation, perhaps representing early substrates for learned controls of intake. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Neural systems for early independent ingestion: Regional metabolic changes during ingestive responding and dehydration.

Regional neural metabolic activity, as assessed by semiquantitative deoxyglucose (DG) autoradiography, was related to dehydration and ingestive behavior in 6-day-old rat pups. During simple ingestive responding, changes in relative DG uptake (representative of changes in neural metabolic activity) occurred primarily in hindbrain sensory and motor nuclei. Producing cellular dehydration resulted in activity changes primarily in the basal forebrain (FB). When Ss were dehydrated and allowed to ingest during the DG-uptake period, activity changes were seen in the hindbrain and FB areas that responded to ingestion or dehydration alone, as well as in regions that were not affected by either manipulation alone. Extracellular dehydration produced fewer and different FB responses in neural metabolic activity. During ingestion, the only effects of extracellular dehydration that overlapped with those of cellular dehydration appeared in circumventricular hypothalamic regions and brain stem motor nuclei. There appeared to be only a limited final common pathway for these 2 types of dehydration-induced drinking. Findings in infant rats depict distributed neural systems subserving ingestion and responding to state change and provide a starting point early in ontogeny for the developmental analysis of neural substrates of ingestive systems. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The ontogeny of feeding in rats: I. Ingestive and behavioral responses to oral infusions.

Reports on 3 experiments with Charles River rat pups. When milk infusions were made through oral cannulas in the front of their mouths, 1–20 day old Ss actively ingested the diet, and their intake was related to the length of deprivation. Ss decreased their ingestive responding after they had consumed large volumes of milk. In addition, 1-, 3-, and 6-day-old Ss, when 24-hr deprived, exhibited an intense behavioral activation in response to milk infusion. The behavioral activation appeared to be stimulated primarily by taste and the opportunity to swallow. Milk infusions did not produce activation in older Ss; their behavior was more exclusively ingestive and food directed. Results demonstrate that (a) from birth, rat pups are capable of an active form of ingestion, independent of normal suckling from the mother; (b) such ingestion is controlled by physiological factors; (c) food has arousing properties in young animals; and (d) as pups grow older, their ingestive responding is refined from a generalized and nondirected activation to specific and directed feeding responses. (57 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Trigeminal deafferentation and ingestive behavior in rats.

For studying the role of orosensory input in the control of ingestive behavior, 46 male albino Wistar rats were subjected to varying degrees of trigeminal deafferentation in 2 experiments. Somatosensory branches that convey touch, temperature, and pain from the oral cavity were sectioned selectively, and muscles of mastication and taste afferents were left intact. Severe intake deficits were produced, including aphagia, adipsia, and prolonged hypophagia, accompanied by a corresponding decrease in body weight. The deficits were proportional to the extent of deafferentation and were most severe when upper and lower portions of the mouth were affected. Although somatosensory impairment affected the organization of the consummatory response, all Ss could bite, chew, and lick. Analysis of feeding patterns showed that minimally (mandibular) deafferented Ss compensated for the consummatory inefficiency by increasing meal duration but failed to initiate meals at the normal rate, thus keeping food intake below normal levels. Results suggest that oral somatosensory input is critical for the mechanisms that regulate ingestive behavior. (45 ref)) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The ontogeny of feeding in rats: IV. Taste development as measured by intake and behavioral responses to oral infusions of sucrose and quinine.

Delivered infusions of sucrose or quinine through cannulas implanted in Charles River CD rat pups' mouths. Intake was measured, and behavioral responses were scored. Responsiveness to sweet and bitter tastes emerged over the 1st 2 wks of postnatal life. Pups showed discrimination between water and sucrose in their mouthing behavior and general activity from 3 days of age, but in their intake only from 6 days of age. Discrimination between water and quinine was not shown until 9 days of age in either behavior or intake. Even then, the stereotypic aversion reactions (paw treading, chin scraping) that characterize the adult response to quinine were not apparent until 12 days. By 15 days of age, preferences for sucrose and aversions to quinine were robust, resembled those of adult rats, and did not depend on previous experience with either solution. (31 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Cholecystokinin conditioning in rats: Ontogenetic determinants.

Low doses (0.12–2.0 μg/kg) of cholecystokinin octapeptide (CCK), administered intraperitoneally, support the formation of conditioned odor preference in neonatal and weanling rats. Exposure to a novel odor was paired with CCK injection, and the rats' olfactory choices were assessed 24 hr later. Rats at 5, 11, and 22 days of age preferred the odor previously associated with CCK, compared with vehicle-injected littermates. In contrast, CCK failed to support olfactory conditioning in 28-day-old rats, whether they were (a) weaned and independently housed, (b) residing with the dam and suckling, or (c) fed only milk. Adult rats also did not establish an odor preference with CCK as the unconditioned stimulus. Thus, CCK's changing impact from positive to neutral probably occurs during the rats' 4th postnatal week and may be related to maturational changes occurring during the final stages of weaning. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Response expectancies and interpretations as determinants of hypnotic responding.

Ss rated the extent to which they expected to respond to each of the suggestions on a hypnotizability scale both before and after the administration of the preliminary hypnotic induction procedure. After the induction, Ss also rated the extent to which they planned to respond actively and passively to each suggestion. Contrary to strong versions of response-expectancy theory, the extent to which Ss planned to adopt an active interpretation predicted behavioral and subjective indexes of hypnotizability even after controlling for the effects of postinduction expectations. In addition, an active interpretation significantly predicted response to suggestion for which Ss held weak and uncertain expectations. The relationship between expectation and hypnotizability was found to be fan-shaped rather than linear. Implications are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Extinction of avoidance responding in rats: The noise-intensity parameter in noise-facilitation of flooding.

60 female hooded rats were given unsignaled avoidance training in the jump-up apparatus developed by the 1st author (1970) and were given a period of flooding followed by extinction testing. During flooding, 4 groups of 15 Ss each received different intensities of continuous white noise. The noise systematically changed spontaneous behavior during flooding and increased the efficacy of flooding in hastening extinction in a roughly monotonic fashion. The louder the noise during flooding, the greater were these effects. Findings are explained in terms of 3 theoretical frameworks: (1) 2-process fear theory, (2) the notion of adaptation to stress, and (3) a sign-tracking analysis. (French abstract) (20 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Habituation of oral responding in adult rats.

The effects of repeated oral stimulation on ingestive responding were investigated in adult rats. A series of brief intraoral infusions of flavored diet was delivered to female rats once every minute through an oral cannula. When the flavor of the infused diet remained constant, significant decreases in mouthing behavior were observed by the end of testing, whereas switching the flavor of the diet during testing resulted in enhanced responding and infusions delivered through gastric cannulas produced minimal effects. Patterns of oral responding were also similar in food-restricted rats. These patterns of responding suggest that adult rats habituate to oral stimulation. Finally, oral habituation led to decreased ingestion, whereas gastric infusions had minimal effects. Thus, oral habituation may represent a mechanism influencing intake in rats at all ages. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The age-related inhibition of motor excitation of the spinal cord in the early postnatal ontogeny of rats

In the experiments on the developing albino rats it was investigated the influence of the lesion of dorsolateral funiculus of the spinal cord on the age-related inhibition of the spontaneous periodic motor activity and late long-lasting discharges evoked by stimulation of n. tibialis controlateralis and recorded in m. gastrocnemius. The relative hyperactivity and increased duration of long-lasting discharges after the end of the second week was observed independently of the age of operated animal (3, 5, 10, 12 days after birth).     

Differentiation of escape and avoidance responding in rats.

Examined escape and avoidance performance in 144 female Holtzman albino rats by factorially arranging immediate or postponed CS and UCS termination with shuttle or bar-press escape and avoidance responses. High levels of avoidance responding occurred only when the shuttle response (running) was both the escape and avoidance response, perhaps reflecting that rats are prepared to run but contraprepared to bar press when threatened by aversive stimulation. In addition, postponed UCS termination reduced avoidance performance drastically while CS termination conditions were without effect. Measures of UCS duration and clock terminations also indicated that immediate UCS termination was superior to postponed termination but additionally showed that this was so because postponed termination seriously impaired escape behavior. Results have particular relevance for how escape responses become anticipatory. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The role of glucocorticoids at the corticosterone level after stress in the early ontogeny of gray rats]

Norway rats were subjected to stress procedure of saline or hydrocortisone injections. The saline-treated rats revealed an increased level of the plasma corticosterone as opposed to hydrocortisone-treated ones. The modification of adrenocortical function with the stress in early postnatal life seems to be connected with changes in hypothalamic catecholamine synthesis and can be prevented with exogenous glycocorticoids.     

Maternal influences on ontogeny of suckling and feeding rhythms in the rat.

Conducted 4 experiments to assess the effects of both maternal and endogenous factors on the ontogeny of nocturnal feeding in the rat. Day and night weight gain was determined in the sighted or blind litters of sighted or blind Sprague-Dawley dams and in young weaned at 15 days of age. It is concluded that sighted dams impose a diurnal milk-intake pattern on their young. The nocturnal patterns of solid-food intake began at 19 days of age. Blind litters also displayed nocturnal feeding when kept with sighted dams, but only until 35 days of age. (30 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Additivity of taste-specific effects of sucrose and quinine: Microstructural analysis of ingestive behavior in rats.

Effects of sweet and bitter tastes on ingestion were studied by timing licking responses. 12 water-deprived rats were given 15-min access to sucrose (SU) solutions (0.00, 1.25, 2.50, and 5.00%) with and without quinine (Q; 0.01%) and to Q solutions (0.00, 0.0025, 0.005, and 0.01%) with and without SU (5.00%). Volume ingested and number of licks increased with SU and decreased with Q. In response to SU, the number of bursts increased, and interlick intervals lengthened. In response to Q, licks to ingest 1 ml of solution, burst number, and percentage of slow licks increased, and burst size decreased. When Q and SU were mixed in the same solution, the pattern of ingestive responses manifested attributes of both tastes. Results suggest 2 separate, parallel systems that operate simultaneously to govern rats' licking behavior. One system expresses the effects of SU on the pattern of ingestion and the other expresses the effects of Q. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Inhibition of ingestive behavior following fourth ventricle bombesin injection in chronic decerebrate rats.

Tested the hypothesis that the effects of 4th ventricle bombesin (BN) injection on feeding require interaction with forebrain neural systems by measuring intraoral sucrose (0.1 M) in tube-fed control and tube-fed supracollicular decerebrate rats after 4th ventricle injections of 1, 5, 10, 20, and 50 ng BN. Fourth ventricle injections of all doses of BN reliably suppressed sucrose intake in both control and chronic decerebrate rats. These results indicate that caudal brain-stem afferent signals produced by 4th ventricle BN injections are integrated by the local neural circuitry of the caudal brain stem, independent of the forebrain systems, to modulate ingestive behavior. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The role of cholecystokinin in conditional compensatory responding and morphine tolerance in rats.

As elaborated in the conditioning analysis of tolerance, cues present at the time of drug administration become associated with the drug effect. A particularly salient cue that may become associated with the drug effect is the pharmacological drug-onset cue inherent to drug administration. Drug-associated cues contribute to tolerance by eliciting a conditional compensatory response that attenuates the drug effect. For example, the early drug effect, having been paired with the subsequent larger drug effect, may elicit the release of antiopioid peptides that counter opioid effects. The role of a putative antiopioid peptide, cholecystokinin-8 (CCK), in the associative mechanisms of opiate tolerance was evaluated. The results of these experiments suggest that a CCK2 receptor antagonist attenuates both the expression of opiate tolerance and the conditional compensatory response hypothesized to mediate such tolerance. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Stimulus determinants of social attraction in rats.

Conducted 5 experiments on the stimulus characteristics mediating 1 rat's attraction for another. 120 Sprague-Dawley and 12 Wistar male albino rats were tested for attraction (physical approach) to (a) a variety of stimulus objects (familiar and unfamiliar objects; stuffed, anesthetized, tethered, and free-moving stimulus rats), (b) rats varying in static stimulus qualities (normal, dyed, shaven, or perfumed), and (c) rats under varying degrees of sensory impairment (normal, blinded, shaven, whiskerless, or anosmic). Variations in sensory capacity or static stimulus characteristics had little effect on social attraction; variations in the dynamic quality of the other rat had large effects. Ss were more attracted to rats which could move and respond to them than to stuffed or anesthetized rats. Results suggest that the quality of behavior and the possibility of interaction between animals mediates gregariousness in rats. (PsycINFO Database Record (c) 2010 APA, all rights reserved)