Trigeminal orosensation and ingestive behavior in the rat.

Used a deafferentation procedure with male Wistar rats to examine the contributions of trigeminal orosensation to control of ingestive behavior. The procedure removed somatosensory input from the mouth while sparing olfaction, lingual taste, vibrissae inputs, and proprioceptive afferents from and efferents to the jaw muscles. Ss with sections of tongue or jaw muscle efferents served as controls. Bilateral trigeminal orosensory deafferentation was followed by effects on ingestive behavior, the magnitudes of which were proportional to the extent of the deafferentation. The trigeminal syndrome includes aphagia and adipsia, impairments in the sensorimotor control of eating and drinking, decreased responsiveness to food and water, and a reduction in the level of body weight regulation. Trigeminal deafferentation spared elementary ingestive movement patterns (biting, licking, and chewing) but disrupted their control by the perioral stimuli. Deficits in food intake varied with the sensory properties of the diet. Recovery of intake took place along a palatability gradient, and recovery of water intake paralleled that of dry food. The chronically reduced body weight was caused by persistent hypophagia and reflected reduced responsiveness to food. Findings suggest a considerable degree of overlap in the neural mechanisms mediating the sensorimotor and motivational control of intake in the rat. (76 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Trigeminal reflexes and ingestive behavior in the rat.

Used photographic, eletrophysiological, and neurobehavioral analyses in 3 experiments with 21 Wistar rats to examine the contribution of trigeminally mediated jaw-opening reflexes to the control of ingestive behavior. During eating and drinking, jaw opening was always preceded by a period of perioral contact with the food or water source (Exp I). Electrical and mechanical stimulation of perioral areas in Ss that were anesthetized with chlorprothixene (0.3 ml) and either ketamine HCl (0.05 ml/100 g) or chloralose (80 mg/kg) elicited jaw-opening reflexes (recorded from the mylohyoid nerve trunk) at short latencies and low stimulus intensities (Exp II). Trigeminal orosensory deafferentation (sparing jaw muscle afferents and efferents, taste, vision, and olfaction) abolished or significantly reduced mouth opening during eating or drinking (Exp III). It is concluded that motivational processes operate through trigeminal reflexes to generate eating in rats. (37 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

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)     

Trigeminal deafferentation and feeding behavior patterns in the pigeon (Columba livia).

Data from a study with 11 White Carneaux pigeons show that after an aphagic period, trigeminally deafferented Ss regulated body weight at reduced levels. The deficit involved was characterized by comparing feeding patterns of deafferented and food-deprived birds with equivalent weight losses. Deafferented Ss showed disproportionate increases in meal size during the early portion of the feeding period but abnormally rapid attenuation of feeding activity in the course of the day, which led to a reduced overall level of food intake. Trigeminal input appears to influence both the size of bouts and the frequency of bout initiation. Findings are discussed in relation to the homeostatic model of intake control and within the framework of food conditioning. (31 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Gustation and ingestive behavior in the rat.

Studied the contribution of taste to the quantitative control of intake and body weight in 15 male Wistar rats. Gustatory deafferentation was produced by combined bilateral section of the chorda tympani and glossopharyngeal nerves and the pharyngeal branch of the vagus nerve. The procedure did not affect the condition of the mouth, impair orientation to sensory stimuli, or severely disrupt the consummatory sequence. Nevertheless, deafferented Ss showed reduced responsiveness to food and water, elevated quinine HCl aversion thresholds, and impaired feeding efficiency. Food and water intake and body weight remained below control levels for at least 40–50 days postoperatively. Food intake deficits were not observed when Ss were offered ad lib pablum, a result suggesting that increased palatability could compensate for decreased gustatory input. The order of recovery of food intake through different diet types suggests a heightened responsiveness to taste stimuli. The effects of gustatory deafferentation are compared with those seen after section of trigeminal orosensory nerves, and the differential contributions of oral taste and oral touch are discussed. (42 ref) (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)     

Trigeminal deafferentation and hunger in the pigeon (Columba livia).

In 2 experiments with a total of 48 White Carneaux and Silver King pigeons, the location and distribution of the pigeon's trigeminal nerve permitted afferentation of the oral region without affecting motor functions. Although trigeminal deafferentation did not affect drinking, it reduced the efficiency of the consummatory response of eating and disrupted motivational processes underlying hunger and weight regulation. Although the 2 types of deficit may be experimentally dissociated, trigeminal deafferentation invariably affected both sensorimotor and motivational mechanisms. The deficits in food intake and weight regulation seen after trigeminal deafferentation in the pigeon resembled some components of the "lateral hypothalamic syndrome" in the rat. Results are related to recent studies of the contribution of peripheral and central oropharyngeal factors to the neural control of food intake in both rat and pigeon. (38 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)     

Abdominal vagotomy alters the structure of the ingestive behavior of rats ingesting liquid diets.

A microstructural analysis of the licking behavior of the rat was used to investigate the effects of total abdominal vagotomy on ingestive behavior. Vagotomy decreased the meal size of milk and 3 concentrations of sucrose. The decrease was due to an increase in the decline in the rate of licking during the meal, suggesting that negative feedback from the gastrointestinal tract was enhanced by vagotomy, perhaps because of accelerated clearance of fluid from the stomach to the intestine. No evidence was found for motor dysfunction of licking or alterations in gustatory sensitivity to the test solution. The results suggest that vagotomy enhanced the strength of an extravagally mediated negative feedback signal from the intestine and that the vagus nerve normally prevents this from occurring by regulating gastric clearance. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

CCK-8 inhibits ingestive behavior in rats with lateral hypothalamic 6-OHDA lesions

Male rats were injected with 6-hydroxydopamine in the lateral hypothalamus and tested for ingestive behavior starting on the day after the injection. The rats did not eat food pellets but readily ingested an intraorally infused nutritive solution. If given three daily intraoral infusions, 6-hydroxydopamine-treated rats defended their body weight and were as sensitive to the inhibitory effect of cholecystokinin octapeptide on intake as controls. Dopamine was reduced by 94% in the dorsal striatum five days after the 6-hydroxydopamine injection. Noradrenaline and serotonin were less markedly affected. Thus, while appetitive ingestive behavior is disrupted, consummatory ingestive behavior and body weight regulatory competence are only marginally affected by massive damage to forebrain dopamine neural networks.     

Trigeminal denervation and operant behavior in the rat.

39 male Wistar rats underwent selective sectioning of trigeminal sensory and motor nerves in 2 experiments to examine the contribution of the sensorimotor system to the control of instrumental responses reinforced with food or water. It was hypothesized that trigeminal denervation would disrupt motivational systems mediating Ss' thirst and hunger. Results show that unilateral sectioning of either Section V sensory or V motor nerves had no significant effect on leverpressing. Bilateral sectioning significantly reduced leverpressing, and the deficit was greatest in Ss with trigeminal motor nerve sectioning. It is concluded that trigeminal orosensory or oromotor denervation disrupts performance on a food- or water-reinforced task in which execution does not require a trigeminally mediated response. Findings are discussed in terms of motivational and reinforcement accounts of instrumental learning. (32 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Abdominal vagotomy attenuates the inhibiting effect of mannitol on the ingestive behavior of rats.

Intact and abdominally vagotomized rats were offered for ingestion during a 30-min period a saccharin and glucose solution or another with 0.1 M mannitol added. The addition of mannitol to the test solution caused a large reduction in intake of intact rats caused by a very rapid decline in the rate of licking during the test. This did not occur with the vagotomized rats. This demonstrates that abdominal vagal nerves are necessary for the inhibitory effect of mannitol on the ingestive behavior of rats. Vagotomized rats also differed from the intact ones by ingesting less of the mannitol-free solution. This was suggested to result from accelerated gastric clearance, leading to abnormally rapid stimulation of negative feedback from the small intestine conveyed to the CNS by extravagal pathways. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Locomotor and exploratory behavior in the rat following bilateral vestibular deafferentation.

Despite many studies of the postural and ocular reflex deficits caused by chronic bilateral vestibular loss in rats and guinea pigs, there have been few systematic studies of the effects of vestibular loss on locomotor activity and exploratory behavior over a period of several months following the lesion. In this study, the authors quantified locomotor and exploratory behavior in an open field maze at 3 weeks, 3 months, and 5 months following bilateral vestibular loss in rats. As a result of bilateral surgical vestibular lesions, rats exhibited a persistent increase in locomotor velocity, duration, and distance traveled, with a marked tendency for increased inner field activity and reduced thigmotaxis. Rats without balance-sense were also found to spend less time exploring the environment, as indicated by a decreased frequency and duration of wall-supported rearings. These results suggest that sudden and complete loss of balance-sense has persistent and complex effects on the way that rats navigate through and explore the environment. (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)     

Limited access to a dietary fat option affects ingestive behavior but not body composition in male rats

Survival, recoverability and sublethal injury of two strains of Listeria monocytogenes, Scott A and an environmental strain KM, on exposure to sea water at 12.8 or 20.8 degrees C was determined using in situ diffusion chambers. Plate counts were used to assess recoverability and injury while 5-cyano-2,3-ditolyl tetrazolium chloride (CTC) reduction was used to determine respiratory activity. T90 values (times for 10-fold decreases in numbers of recoverable cells) on non-selective medium (trypticase soya agar with 0.6% yeast extract) at 12.8 and 20.8 degrees C were 61.7 and 69.2 h for L. monocytogenes Scott A, and 103.0 and 67.0 h for L. monocytogenes KM, respectively. On selective medium (Oxford agar), T90 values at 12.8 and 20.8 degrees C were 60.6 and 56.9 h for L. monocytogenes Scott A, and 83.0 and 65.9 h for L. monocytogenes KM, respectively. With Scott A, the percentage of sublethally injured cells at 12.8 and 20.8 degrees C was 1.7 and 17.7%, respectively, while for KM the values were 19.0 and 1.6%, respectively. The fraction of cells reducing CTC but which were not recoverable on plating progressively increased on exposure to sea water. Listeria monocytogenes KM challenged at 58 degrees C showed an apparent increase in heat resistance after exposure to sea water at 20.8 degrees C for 7 d (D58 = 2.64 min) compared with before exposure (D58 = 1.24). This increase in thermal resistance was not apparent at temperatures greater than 63 degrees C, and analysis of the best-fit regression lines fitted to the thermal data obtained from the two cell populations indicated that their thermal resistance was not significantly different (P > 0.05) over the temperature range tested (58-62 degrees C).     

Effects of poisoning on predatory and ingestive behavior toward artificial prey in rats (Rattus norvegicus).

Ingestion of novel prey by vertebrate predators that is followed by illness typically decreases the predators' eating the prey more readily than their pursuing or killing it. We used artificial prey-food items (rolling ball bearings that predicted food pellets) to model and extend this finding in laboratory rats. During daily experimental sessions presentations of a novel bearing–food combination were intermixed with presentations of a familiar bearing–food combination. The poisoned animals received lithium chloride injections after each session. Poisoning markedly decreased ingestion of the novel food without decreasing the frequency of contact (nose, seize, carry, or chew) with the novel bearing predicting that food. However, poisoning did significantly decrease the average duration of contact with the novel bearing. Poisoning did not decrease behavior toward the familiar food and bearing. After moderate exposure to pairings of the novel food and bearing, poisoning decreased behavior toward both novel and familiar food and bearings. The results indicate that important aspects of predation can be simulated and examined in the laboratory by using artificial prey-food items. These results also support the conclusions that predatory behavior and ingestion reflect separable modes of behavior and that the presence of novel prey interferes with the generalization of poisoning effects to familiar prey. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Alternating ingestive and aversive consummatory responses suggest a two-dimensional analysis of palatability in rats.

Examined the hedonic response to a taste which is usually regarded as the product of a central integration of gustatory afferent information that ends in a single decision about the nature and intensity of the response to be given. The response is often characterized as a point lying along a single dimension of palatability, stretching from strongly positive to strongly negative. Two experiments dealing with consummatory responses in male Sprague-Dawley rats suggested that the final response is not made on the basis of a single central analysis of taste information, but rather is the result of a competition between 2 separate systems that are activated by tastes. A single oral infusion of a taste solution may elicit rapid alternation between ingestive and aversive consummatory responses. Such alternation is better interpreted as due to a simultaneous activation of 2 palatability dimensions than as a reflection of neutral palatability. When increases in the magnitude of aversive responses are produced by taste mixtures, there is not necessarily a reciprocal decrease in ingestive responses. This asymmetry supports the hypothesis of independent palatability dimensions. (26 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The ontogeny of feeding in rats: III. Thermal determinants of early ingestive responding.

High ambient temperatures (38°C) stimulated high spontaneous levels of activity and high frequencies of behaviors normally associated with ingestion (mouthing and probing), particularly in young, 3- and 6-day-old Charles River CD rat pups (Exp I). The level of spontaneous behavior was highly correlated with body temperature and also depended on deprivation condition. Temperature played an important role in determining responses to food stimuli as well. When Ss were fed by oral infusion (Exp II) or by placing milk on the floor beneath them (Exp III), warm ambient temperatures were required for active ingestion. In Exp IV, body temperature and ambient temperature were manipulated independently to assess their relative importance for Ss' feeding behavior. Ss with a low (29°C) or normal (34°C) core temperature at the start of testing were fed in either a 24°C or a 34°C ambience. Regardless of body temperature, Ss' levels of intake, activity, mouthing, and probing were higher in a warm than in a cool ambience. Therefore, the suppressed ingestive behavior of Ss fed at cool temperatures occurred not simply because Ss became hypothermic and inactive. Perceived warmth appears to be a significant contextual cue that regulates pups' responses to food stimuli. (29 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)