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 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)     

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)     

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)     

Acoustic startle reflexes in the rat during consummatory behavior.

Conducted 4 experiments, using a total of 18 male albino Holtzman rats. Auditory startle reflexes were elicited in thirsty Ss when they were drinking water or were between drinking bouts. The reaction was greater during drinking, this enhancement developing over the 1st few seconds after drinking onset. The startle reaction was lowest immediately after the termination of drinking. Reflex enhancement was reduced when thirsty Ss drank milk rather than the more preferred water. The reflex was smaller with increased water deprivation, but enhancement produced by drinking was apparent at all levels of deprivation studied-satiety to 4-days deprivation. The inhibitory effect of a preliminary stimulus was not affected by consummatory behavior. Attention is drawn to suggestive parallels between these behavioral effects and other consequences of consummatory activity, primarily having to do with electrophysiological events and arousal processes. (18 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Contribution of ingestive behaviors to taste-aversion learning in the rat.

Conducted 3 experiments with male Sprague-Dawley rats (N = 132). Ss tasting but not ingesting a flavored solution prior to toxicosis acquired weaker aversions to the flavor than Ss that actively consumed the CS during conditioning. Taste was isolated from ingestion either by curarizing the Ss or by infusing a flavored solution very rapidly into the oral cavity of non-water-deprived Ss. Control groups showed that the facilitatory effect of ingestion on taste-aversion learning did not depend on the consumption of very much of the CS solution. (20 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Failure in conditioning of ingestive instrumental reflexes in the absence of ororhinopharyngeal stimuli [proceedings

A case of respiratory distress is reported following lung decortication. Of a 331/min applied respiratory volume 90% was lost due to the multiple alveolar leakage. The lung could be inflated only when the chest was closed and several Bülau drains with powerful suckers were inserted. When the lung surface came in contact with the chest wall, the lossof tidal volume could immediately be reduced and respiration was possible again.     

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)     

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)     

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)     

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)     

Neocortex and feeding behavior in the rat.

Consummatory behavior and weight-regulation capacity were measured in 12 normal male Long-Evans rats and in 43 similar Ss that survived complete (C), sequential unilateral (U), anterolateral (A) , or posterior (P) neocortical ablations. Groups C and A displayed aphagia and adipsia followed by a sequence of recovery stages qualitatively identical to, but shorter than, recovery typically seen following lateral hypothalamic lesions. After recovery, Group C displayed long-term effects of finickiness and prandial drinking. These effects and a measure of recovery of body-weight-regulation capacity were significantly intercorrelated with lesion size, and body-weight set point remained significantly lower than normal. Group U was relatively unaffected by the 1st unilateral ablation and showed, relative to Group C, facilitated recovery of consummatory behaviors following the 2nd ablation, but displayed the long-term effects. Group P, though significantly affected by the lesion, did not display the pattern or intensity of effects described for the other bilaterally ablated groups. (47 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Altered ingestive behavior, weight changes, and intact olfactory sense in an APP overexpression model.

Transgenic APP23 mice were generated to model Alzheimer's disease. The APP23 model develops pathological features, learning deficits, and memory deficits analogous to dementing patients. In this report, transgenic mice exhibited several behavioral disturbances indicating the presence of neuropsychiatric symptoms of dementia. Aiming to verify whether the model also develops other behavioral problems, the authors investigated ingestive behavior in APP23 males of 3, 6 and 12 months. In addition, body weights of a naive male group were longitudinally monitored starting at weaning. Olfactory acuity was evaluated in mice of different age groups. Although olfactory functioning of APP23 mice appeared intact, they drank more and took more food pellets compared with wild-type littermates during a 1-week registration period. From the age of 4.5 weeks onward, APP23 males weighed significantly less than their control littermates, whereas this difference became more prominent with increasing age. Our results suggest the presence of a hypermetabolic state in this model. This is the first report, evidencing the presence of changes in eating and drinking behavior in a single transgenic Alzheimer mouse model. (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)     

Maternal behavior in the virgin and lactating rat.

Observed the onset of maternal behavior in 20 Sprague-Dawley virgin female rats during pup induction, and later compared their behavior with that of 8 lactating mothers. During induction, the onset was sudden rather than gradual, and during maternal care their behavior was similar in almost all respects to that of lactating mothers. Reinduction of maternal behavior in virgins occurred with a shorter latency than during the original induction, and induction of maternal behavior in formerly lactating mothers was equally short. Results support the idea that postpartum maternal behavior is nonhormonally based. (40 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Hysterectomy-induced maternal behavior pregnancy in the rat.

Performed hysterectomies between the 10th and 19th day of pregnancy, and tested females with pups for the onset of maternal behavior starting 0, 24, 48, or 72 hr after surgery. Ss were 394 Charles River female rats. Pups remained with females overnight, and testing was repeated daily with fresh pups until females exhibited maternal behavior. Latencies for the onset of maternal behavior were shorter after hysterectomy on the 10th and 16th days of pregnancy than in intact pregnant Ss at the same stages of pregnancy; latencies become shorter, the later the termination of pregnancy. When the ovaries were removed along with hysterectomy during pregnancy, short-latency maternal behavior no longer was exhibited. Pregnant Ss were tested during the last 40 hr of pregnancy: nest building began at 34 and retrieving at 28 hr prepartum. The effect of hysterectomy during pregnancy on ovarian secretion of estrogen and progesterone is reviewed, and it is concluded that the rise in estrogen secretion, which follows hysterectomy during pregnancy, is most likely the cause of the rapid onset of maternal behavior after hysterectomy. A similar proposal is made for the prepartum onset of maternal behavior in intact pregnant females. (50 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Cocaine alters behavior in the rat fetus.

Changes in motor behavior and sensory responsiveness were characterized in rat fetuses on Gestational Day 21 after acute administration of various doses of cocaine. An increase in fetal motor activity was evident in the 3 highest doses (5, 10, and 20 mg/kg). Cocaine-exposed Ss showed reduced facial wiping in behavioral bioassays of cutaneous sensitivity (10 and 20 mg/kg) and chemosensory responsiveness (20 mg/kg). Changes in other behavioral measures indicated that fetuses detected and responded to these stimuli, suggesting that reduced facial wiping was due to a disruption of sensorimotor integration or motor coordination. Study of the fetus in vivo can provide insights into the mechanisms of cocaine's deleterious effects on CNS and behavioral development. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Human thalamic nucleus mediating taste and multiple other sensations related to ingestive behavior

Until now, taste was the only primary sensory modality for which the human central nervous system pathways were unknown. We report sensations evoked by stimulation at microampere current levels in the region of the human thalamic nucleus (ventralis caudalis parvocellularis internis) corresponding to the monkey taste relay nucleus. Stimulation in this region during awake neurosurgical procedures evoked special visceral/somatic (taste/pungent smell), general visceral (fullness of a hollow viscus), as well as painful and nonpainful general somatic sensations. General somatic or visceral sensation was evoked by stimulation at 80% of sites where special visceral/somatic sensation was evoked. These results suggest that primate taste relay mediates multiple sensations in addition to taste.     

The propensity for nonregulatory ingestive behavior is related to differences in dopamine systems: Behavioral and biochemical evidence.

Investigated the relation between properties of dopaminergic neural systems and the predisposition to exhibit nonregulatory ingestive behavior in 54 male Long-Evans rats. It was found that Ss that ate and drank during electrical stimulation of the lateral hypothalamus (ESLH) showed greater behavioral sensitization to a series of amphetamine injections (3 mg/kg) than those that did not exhibit ingestive behavior during ESLH. In addition, footshock stress produced a greater increase in forebrain dopamine utilization in Ss that engaged in nonregulatory ingestive behavior. This evidence is consistent with the hypothesis that there are individual differences in the responsiveness of forebrain dopamine systems that are related to the behavioral predisposition to exhibit nonregulatory ingestive behavior. (51 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)