The relation of feeding and activity following septal lesions in rats.

The patterns of intake of liquid diet (Exp I) and water (Exp II) were recorded in 12 female Long-Evans diet-deprived rats with septal lesions and 13 neurologically intact controls during the 1st hr of diet access. The occurrences of grooming, resting/sleeping, and exploring were also recorded. Findings show that both groups consumed similar amounts of diet in 1 meal during the 1-hr diet access period. Controls consumed the meal in 1 prolonged bout of eating, while lesioned Ss consumed the meal in numerous small bouts of eating. Lesioned Ss were active for longer periods, exhibiting continuous alternation of brief bouts of eating, drinking, exploring, and resting throughout the meal. In tests in which water was not available during the diet access period, both groups increased their intrameal bout size, but lesioned Ss still showed much smaller bouts of ingestion than did controls. Data suggest that the small-bout pattern of ingestion may reflect a general disruption in the control of behavioral sequences, rather than processes uniquely related to the regulation of eating or drinking. (16 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Independent effects of estradiol on water and food intake.

Conducted 6 experiments to examine the effects of estradiol on ingestive behaviors of guinea pigs. Estradiol treatment was found to reduce water intake independently of its actions on food intake and body weight. In the 1st experiment, minimum intake and body weight of 17 intact female guinea pigs coincided with rupture of the vaginal membrane, the estimated time of ovulation. In Exp II, injections of 3 μg of estradiol benzoate (EB)/day to 7 ovariectomized females significantly depressed food intake, water intake, and body weight, compared with 7 Ss that received oil injections. Reducing food rations to 30% below ad lib levels in Exp III by itself had no significant effect on drinking in ovariectomized Ss. In Exp IV, therefore, ovariectomized females were first placed on a food ration 30% below ad lib levels and then injected daily with either 3 μg of EB or oil. Compared with oil injections, these EB injections significantly reduced water intake, while food intake did not decline significantly. Findings indicate that estradiol operates through different mechanisms to affect water intake and food intake. (40 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Influence of drinking history on food-deprived drinking in the rat.

Investigated the role of drinking during development in 40 male hooded Long-Evans rats. Experimental Ss were deprived of water during rearing; ingestion of lettuce provided for sufficient fluids. Body weight, feeding, drinking, and urine volume over successive food deprivation periods were compared with normally reared controls. The lettuce-reared Ss drank less water and ate less lettuce when food deprived, but did not differ from normal Ss in drinking or in lettuce intake when food was available ad lib. It is suggested that lettuce-reared animals drink water principally in response to fluid deficits. Other research indicates that the drinking of normally reared rats anticipates fluid deficits and is not initiated by events related to the need for water. The present results suggest that this anticipatory drinking is acquired. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Oropharyngeal control of ingestion in rats: Acquisition of sham-drinking patterns.

Conducted 3 experiments with female Sprague-Dawley rats with esophageal fistulas (3 Ss in Exp I, 3 in Exp II, and 4 in Exp III). Offered a concentrated glucose solution, Ss sham drank relatively small amounts on the 1st session, whether or not such a solution was familiar. Intake rose to high levels over ensuing sham-drinking sessions, showing that the initial small volumes were not attributable to fixed properties of the solution itself. The gradual acquisition of copious sham drinking was not affected by previous "practice" at sham drinking other commodities; it was not simply an alteration in motor habits. The gradual acquisition of the sham-drinking pattern did not occur with more dilute solutions; in response to these, sham drinking was copious and continuous from the onset. The following conclusions are made: (a) Rats must learn to respond, by continuous drinking, to the absence of the postingestive inhibition normally produced by concentrated solutions. (b) No such learning is required in the case of more dilute solutions. This is further evidence that controlling factors with differing properties operate at different levels even of the single commodity, glucose in solution. (17 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Drug states as discriminative stimuli in a flavor-aversion learning experiment.

Injection of poison into rats after they drank in the presence of stimulus compounds of a drug state and a flavor resulted in little stimulus control by the drug state. In Exp I, half of the 16 male Sprague-Dawley rats were poisoned after drinking salt water while stimulated with amphetamine and after drinking sugar water while sedated with pentobarbital, but they were not poisoned after salt–pentobarbital (BY) or sugar–amphetamine (AX) combinations. The other half were subjected to counterbalanced procedures. Poisoning occurred after AX and BY stimulus combinations but did not occur after AY and BX combinations. In Exp II, 32 Ss were poisoned only after consuming a particular flavored solution (salt or vinegar) in a particular state (pentobarbital or undrugged); that is, if AX was poisoned, BX, BY, and AY were experienced without poisoning. There was complete counterbalancing of flavors and drug states. Exp II, with 23 Ss, was similar except that amphetamine was used instead of pentobarbital. In both experiments, there was some discrimination learning based on the drug state, but it was extremely weak. (21 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Abdominal vagotomy disrupts food-related drinking in the rat.

In 2 experiments with a total of 41 Sprague-Dawley albino rats, Ss with complete subdiaphragmatic bilateral transection of the abdominal vagus (Vgx-C) showed disordered food-related drinking when drinking water in temporal association with a meal of dry food after 5-hr food deprivation and when drinking water in association with a liquid meal after 24-hr food deprivation. The Vgx-C Ss drank after significantly longer latencies and drank significantly less water in 1 hr than did sham-vagotomized (Sham) Ss after eating the same size meal (solid or liquid). Ss with incomplete vagal transection (Vgx-I) ate and drank like Shams. Water intake of Sham and Vgx-I Ss correlated positively with the meal size of solid food, but the water intake of Vgx-C Ss did not. The failure of Vgx-C Ss to drink water normally when food was ingested was not due to failure of a food stimulus to reach the intestine, because Vgx-C and Sham Ss emptied equivalent volumes of liquid food from the stomach into the intestine within 10 min of food entering the stomach. Results indicate that the abdominal vagus is an important neurological substrate for food-related drinking in the rat. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Conditioned aversion to distinct environmental stimuli resulting from gastrointestinal distress.

In Exp I, 40 male Sprague-Dawley-derived rats subjected to apomorphine-induced malaise following a 2-min placement in a black compartment avoided this black compartment significantly more than 10 controls in a choice situation. The degree of aversion, however, was substantially reduced when Ss were provided water (or saccharin) in the black compartment during conditioning and testing. Ss learned to suppress consumption of fluid in the black compartment. In Exp II, 10 Ss were made ill in the black compartment. Later, when drinking saccharin (or saline) preceded placement in the black compartment, Ss learned to suppress consumption of that fluid. The black compartment had become a conditioned reinforcer for taste aversion. (19 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of 4-hydroxyamphetamine on in vivo brown adipose tissue thermogenesis and feeding behavior in the rat.

Examined the influence of 4-hydroxyamphetamine (4-OHAM) on food and water intake and in vivo brown adipose thermogenesis in 2 experiments with 22 female Long-Evans rats. In Exp I, Ss were treated with 4-OHAM (0.25, 0.50, 1, or 2 mg/kg, ip) prior to assessment of interscapular brown adipose tissue (IBAT) thermogenesis. The 4-OHAM treatment induced dose-dependent activation of IBAT thermogenesis consistent with the enhanced serum levels of norepinephrine and epinephrine observed in 4-OHAM-treated Ss immediately after temperature measurement. In Exp II, the influence of 4-OHAM on food and water intake was assessed during 120-min test intervals in Ss fed food and water ad lib. Although there was a trend for 4-OHAM to increase water intake, there was no significant effect of 4-OHAM (0.40, 0.80, 1, 2, and 4 mg/kg) on either food or water intake. Data suggest that IBAT thermogenesis does not play a role in the anorexia induced by amphetamine or in the regulation of feeding. (19 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

ACTH and ACTH4–20 modification of neophobia and taste aversion responses in the rat.

A series of 6 experiments assessed the effects of ACTH and the ACTH analog ACTH4–20 on drinking in conditioned taste aversion and neophobic situations using a total of 168 male Sprague-Dawley rats as Ss. Both substances delayed the extinction of a conditioned taste aversion established by a single pairing of lithium chloride with milk (Exp I). However, in this situation, the ACTH parent peptide was more potent behaviorally. ACTH supressed milk consumption in Ss with no toxicosis experience (Exp II). This effect was apparently not due to the conditioning of a taste aversion (Exp III) with ACTH serving as a weak aversive UCS. Exogenous ACTH (Exp IV) or ACTH4–20 (Exp V) did not enhance neophobia; however, repeated injections of ACTH suppressed drinking. This ACTH suppression was related to the familiarity/novelty of the substance being consumed. The neophobic response to milk was not accompanied by pituitary-adrenal activation (Exp VI). Both neophobic and conditioned taste aversion situations appear to be useful for assessing peptide effects on consummatory behavior. (36 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The role of taste in dietary self-selection in rats.

Conducted 3 experiments with 78 male albino Harlan and Sprague-Dawley rats in which Ss were subjected to 2 degrees of gustatory deafferentation—either the chorda tympani was sectioned alone or in combination with the glossopharyngeal nerve and the pharyngeal branch of the vagus. Ss were then presented with 2 diets, only 1 of which contained protein. Findings reveal that, after surgery, deficits were observed in body weight, food and water intake, and diet selection that were proportional to the extent of deafferentation. Approximately 76% of the Ss increased protein and decreased carbohydrate intake, but all Ss continued to select a nutritionally balanced diet (Exp I). When subjected to a nutritional challenge of intragastric protein or carbohydrate supplementation, the Ss compensated for calories and nutrients by selectively adjusting oral intake (Exp II). In saccharin preference tests, the preference as well as the total consumption of the test solutions was reduced (Exp III). Results support the hypothesis that dietary selection pattern of an animal not only reflects intrinsic factors (metabolic/physiological state) but also extrinsic factors such as the pallatability and accessibility of the diet. Findings are contrasted to the effects of oral somatosensory deafferentation and are interpreted as a change in preference within the limits of metabolic requirements. The different roles/mechanisms of the 2 sensory systems in regard to dietary self-selection are discussed. (36 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Stress and ulceration in the glandular and nonglandular portions of the rat's stomach.

Previous studies indicate that conditioned fear and conflict produce ulceration in the nonglandular portion of the rat's stomach (rumen), while immobilization produces ulceration in the glandular portion (corpus). The present 3 experiments were conducted with Maudsley Reactive, Maudsley Nonreactive, and male Sprague-Dawley rats (N = 66). Exp I and II tested the course of ulceration in the corpus and rumen under stress conditions. Ulceration was induced in the corpus by partial restraint. Ulcerated Ss were then exposed to conditioned fear for 72 hrs (Exp I) and 48 hrs (Exp II) and were compared with controls. Exp I showed that glandular lesions healed while nonglandular lesions developed in food-deprived Ss. Nonglandular ulcers did not appear during the 48 hrs of Exp II. Exp III showed a positive relationship between rumenal ulceration and food deprivation. Rumenal ulceration induced by conflict and conditioned fear procedures mainly seems to reflect the suppression of food intake by these procedures. (22 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of lesions in the basolateral amygdala on fluid intake in the rat.

Conducted 6 experiments with 33 rats with bilateral lesions in the lateral amygdaloid region and 22 intact controls. Drinking response to hypertonic saline, a cellular thirst stimulus, and to isoproterenol, probably an extracellular thirst stimulus, was normal in lesioned Ss. The overnight water intake of the lesioned Ss was a little higher than normal. However, the lesioned Ss showed a major impairment in learning to avoid ingesting a poisonous solution of LiCl when they were thirsty and an increased preference of 25% sucrose in a 2-bottle sucrose-water test. It is concluded that the basolateral region of the amygdala is involved in the effects of previous experience on drinking and not primarily in the cellular or extracellular controls of drinking. (25 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Dietary self-selection in intact, ovariectomized, and estradiol-treated female rats.

Six experiments with 84 Long-Evans rats investigated the effects of estrogenic stimulation on diet selection in intact estrous-cycling Ss, ovariectomized (OVX) Ss, and OVX Ss given estradiol benzoate (EB) hormone replacement therapy. In Exp I, OVX was associated with the nearly exclusive choice of the more calorically dense of a pair of diets varying in the concentration of fat, carbohydrate (COH), and protein, an effect that was decreased by EB. In Exp II, dietary self-selection was examined in intact estrous-cycling Ss given access to an isocaloric diet triplet of fat, COH, and protein. Total caloric intake and body weight did not vary across the estrous cycle. However, fat intake increased; COH and, to a lesser extent, protein intake decreased. An opposite diet selection occurred during diestrus. In Exp III, OVX resulted in progressive increases in COH and protein intake, with a concurrent decrease in fat consumption. EB partially reversed this diet selection profile (Exp IV). Results were confirmed by diet pairs with both naturally occurring and experimentally produced estrogenic stimulation (Exps V and VI). Data are consistent with previous findings showing estrogenic reduction in COH intake with standard high-COH commercial diets. (32 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Inhibition of lordosis in rats by the antiestrogen CI-628 in the absence of progesterone.

Assessed whether the ability of the antiestrogen CI-628 to inhibit estrogen-stimulated lordosis behavior (LB) in adult ovariectomized Sprague-Dawley rats depends on its interference with the synergistic effects of estrogen with progesterone. In Exp I the effect of CI-628 was contrasted in Ss brought into estrus by estradiol benzoate (EB; 0 or 3 μg/.1 ml) combined with progesterone (P; 42 or 500 μg/.1 ml) vs 4 daily injections of EB (without P). CI-628 effectively antagonized LB in both conditions. In the absence of CI-628, Ss receiving P had significantly higher LB scores than the 4-day EB controls. In Exp II Ss receiving CI-628 on only the 1st 2 of 4 days of EB injections had decreased LB scores unless P was also given on the day of testing. This suggested that the EB from the latter injections was not acting as a progestin "mimic." In Exp III LB stimulated by EB (without P) was inhibited by CI-628 in Ss that were both ovariectomized and adrenalectomized. This suggested that adrenal progestins were not involved in the ability of CI-628 to inhibit LB. Results suggest that the mechanism of action of CI-628 for the inhibition of LB does not depend on its ability to antagonize an estrogen-induced increase in neural progestin receptors. Implications for estrogen-mediated behaviors, for which CI-628 has little or no antagonistic effects, are discussed. (36 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Conditioned taste aversion in lean and obese rats with ventromedial hypothalamic knife cuts.

Assessed the development of a conditioned taste aversion (CTA) in 60 female Sprague-Dawley rats made hyperphagic with parasagittal knife cuts in the ventromedial hypothalamus (VMH). Ss were water deprived and presented with a .1% saccharin solution paired with injections of either LiCl or NaCl. In Exp I, VMH Ss tested at a nonobese weight level did not differ from sham-operated controls in acquisition and extinction of the CTA. In Exp II, moderately obese VMH Ss displayed a stronger CTA than did sham-operated controls as evidenced by slower extinction. A 2nd group of obese VMH Ss given an amount of LiCl equivalent to that given to the controls also displayed retarded extinction of the CTA. Results reflect an obesity-induced suppression in appetitive motivation. (29 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Interaction of hunger and thirst in the motivational arousal underlying hoarding behavior in the rat.

Conducted 3 experiments with 25 male Wistar rats in which hoarding of food could be elicited by a 16-hr food deprivation schedule. It was found that (a) prolonged water restriction, with food ad lib, failed to induce hoarding in spite of spontaneous reduction in food intake and a fall in body weight to below levels normally critical for the onset of hoarding. Thus, different physiological deficits are not necessarily equivalent or additive in elicitation of food hoarding, and water lack may suppress it. (b) Hoarding behavior was released in water-deprived Ss by a drink of water. A 30-min delay to allow absorption of the water significantly enhanced the release of hoarding. Air drinking by water-deprived Ss did not release hoarding. Thus, absence of hoarding during water lack may be caused by an active process that can be inhibited or canceled by postingestional effects of drinking but not by oropharyngeal stimulation mimicking water signals. (c) Although water lack prevented hoarding in response to self-imposed fasting, hoarding ensued at maximal rates when further food deprivation was superimposed. Thus, inhibition of hoarding by dehydration operates subtractively, not multiplicatively, and with free access to food, the inhibition of hoarding by thirst tends to be balanced exactly by the facilitatory effect of concomitant fasting; thus superadded food deprivation can take full effect. It is concluded that in states of motivational arousal, specific inhibitory mechanisms may inhibit subtractively certain activities biologically irrelevant to prevailing physiological needs. (25 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of intrahippocampal administration of colchicine on incentive contrast and on radial maze performance.

Examined the behavior of rats given intradentate injections of colchicine (COL). In Exp 1, COL-treated, artificial cerebrospinal fluid (CSF)-treated, and untreated Ss did not differ in the intake of 32% and 4% sucrose solutions, nor did they differ in degree of successive negative contrast when the 32% solution was changed to 4% sucrose. In Exp 2, the COL-treated and CSF-treated Ss did not differ in degree of suppression in the intake of a 0.15% saccharin solution when it preceded 32% sucrose in once-daily pairings (anticipatory contrast), nor did they differ in reversal performance when saccharin–sucrose and saccharin–saccharin pairings were reversed. In Exp 3, the COL-treated Ss were substantially impaired in radial-arm maze performance compared with CSF-treated controls. Results suggest that a completely functioning hippocampus is not necessary for the memory of reward quality, the comparison of rewards, the suppression of behavior when reward is decreased, the formation of associations between 2 levels of reward, and the reversal of this association, as long as these processes are reflected in consummatory behavior. Data are interpreted in terms of differences between instrumental behavior and sensory memory and/or consummatory behavior. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Latent inhibition experiments with goldfish (Carassius auratus).

Examined evidence of latent inhibition in a series of experiments with goldfish. In Exp I, 12 Ss were given nonreinforced preexposure to a color that subsequently predicted shock in an activity conditioning situation; their performance did not differ from that of 12 control Ss preexposed to a markedly different color. In Exp II, 12 Ss given nonreinforced preexposure to a tone and an unstimulated control group of 12 Ss were trained in an appetitive situation, with the tone serving either as a conditioned excitor or as a conditioned inhibitor. Preexposure had significant effect in the conditioned excitation training, but it reduced the level of responding both to the positive stimulus and to the negative compound in the conditioned inhibition training. In Exps III and IV, classical aversive conditioning was studied in the shuttle box. In Exp III, excitatory conditioning to a color was found to be impaired (relative to the performance of nonpreexposed control Ss) as much by nonreinforced preexposure to the training color as by nonreinforced preexposure to a markedly different color; substantial variation in amount of preexposure was without significant effect. In the conditioned inhibition training of Exp IV, 12 Ss with nonreinforced preexposure responded less than did 12 unstimulated control Ss, both to the positive stimulus and to the negative compound. Results demonstrate that the effect of preexposure on goldfish is their reduction of general responsiveness or level of arousal. (47 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Oral somatosensory factors in dietary self-selection after food deprivation and supplementation.

In 2 experiments with 72 male albino Sprague-Dawley rats, trigeminally deafferented Ss were subjected to nutritional stresses while being allowed to balance protein and carbohydrate intake from 3 separate dietary fractions. Partially trigeminally deafferented Ss that had recovered a normal protein ratio (protein/total intake) underwent total food deprivation (Exp I) or intragastric (IG) supplementation of protein or carbohydrate suspensions (Exp II). In response to deprivation, control Ss increased protein intake above ad-lib levels, but not carbohydrate intake. In response to IG supplementation, they decreased protein intake disproportionately more than carbohydrate intake when the fluid consisted of protein and vice versa when the fluid consisted of carbohydrate. The recovered deafferented Ss showed no selective increase in protein intake after deprivation and no differential compensation to nutrient supplementation. This suggested that recovery of the protein ratio after partial trigeminal deafferentation could not fully replace the function of trigeminal somatosensory input. The possible roles of other orosensory and of postingestional factors for recovery are discussed. (16 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)