Effects of cholecystokinin on taste preference and sensitivity in rats.

Determined, in 3 experiments with 10 Long-Evans rats, that cholecystokinin octapeptide (CCK-8) reduced the amount consumed or the number of licks of several concentrations of sucrose in short-term tests with Ss that were hungry, satiated, or fed ad lib. The suppressive effect of CCK-8 was generally smaller in the hungry than in the satiated or ad-lib condition. In the satiated and ad-lib conditions, there was no effect of sucrose concentration on the magnitude of the CCK-8 effect. In hungry Ss, the concentration-intake function for sucrose was lowered and flattened by both CCK and natural satiety. To determine whether a taste change is involved in this short-term reduction of sucrose intake, integrated chorda tympani responses were measured before and after iv infusions of CCK-8 or NaCl. The peak response to .3 M sucrose significantly increased after 2 5-μg infusions of CCK-8. Peak and tonic responses to sucrose and saline tended to increase after CCK-8 but not NaCl infusions. Results suggest that CCK-8 reduces sucrose intake in situations in which postingestional factors are minimal and that sucrose concentration has little effect on the size of this suppression. A change in perceived taste intensity or quality may play a role in the inhibitory effect of CCK-8 on intake. (33 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of early posthatch exposure to intermittent light on visual flicker rate preference in chicks.

Gave independent groups of newly hatched White Leghorn chicks (N = 45) 15 hr of continuous exposure to several rates of flashing white light during the period when the naive preference for a 4 flash/sec rate over a nonflashing light began to emerge. Tests conducted immediately following termination of exposure showed that although this treatment generated a marked reduction in locomotor activity and distress calling, it produced no change in the Ss' naive flash rate preference. (23 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of exposure to stressors of varying predictability on adrenal function in rats.

For 5 days, rats were exposed to shocks that were signalled by a light 0, 33, 66, or 100% of the time. Basal hormone levels and responses to a light-shock pair were measured daily. Greater predictability was associated with higher basal plasma corticosterone and norepinephrine levels indicative of chronic stress. Habituation of the corticosterone response was also less in the groups with greater predictability. However, predictability did not affect plasma prolactin or epinephrine responses. Because the endocrine systems responded differently, it is unlikely that the changes were due to a unitary process. Greater predictability appeared to be more stressful in this paradigm. Both associative and nonassociative factors have major roles in determining the hormonal responses to repeated presentation of stressors. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of prenatal exposure to cocaine on conditional discrimination learning in adult rats.

Adult male rats that were gestationally exposed to cocaine and control offspring were trained on an instrumental conditioning task for assessment of the acquisition and reversal of an appetitive conditional discrimination based on olfactory cues. Offspring were derived from Sprague-Dawley dams that had received subcutaneous/ly (sc) injections of 40 mg/kg/3 cc cocaine hydrochloride (C40) daily on Gestational Days 8–20, pair-fed (PF) dams that were injected with saline, nutritional control dams (NC) that received saline injections, and nontreated control dams (LC). There were no differences among the prenatal treatment groups in acquisition of the barpress response or response rate throughout all phases of training. All prenatal treatment groups required approximately the same number of sessions to criterion on the initial odor discrimination. In contrast, adult C40 offspring required more sessions to acquire the reversal of the conditional discrimination than did animals from the other treatment groups (PF, NC, and LC). In addition, even at criterion performance for acquisition of the reversal discrimination, C40 animals exhibited lower accuracy on the 1st 10 responses and made significantly more errors before the 1st reward. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of prenatal exposure to cocaine on Morris water maze performance in adult rats.

The spatial memory of adult rats prenatally exposed to cocaine and that of control offspring was assessed using the Morris water maze. Offspring were derived from Sprague Dawley dams that received subcutaneous injection of 40 mg/kg/3 cc cocaine hydrochloride (C40) daily on gestational Days 8-20, pair-fed dams injected with saline, or nontreated control dams. After acquisition, the platform was moved to a new location (reversal phase). Probe trials were conducted at the end of acquisition and reversal training. On the 1st acquisition day, adult male and female offspring prenatally exposed to cocaine required significantly more time and traversed a greater distance to find the hidden platform than did control offspring. Despite these initial differences observed in C40 offspring performance, all of the rats were performing at equivalent levels at the time probe trials were conducted. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of dietary amino acid pattern on food preference behavior of rats.

Conducted an experiment with 46 male Holtzman rats in which Ss offered a diet in which there was an imbalance of amino acids together with a protein-free diet ate very little of the imbalanced diet. However, when Ss that were selecting the protein-free diet were fed in single meal (1-3 gm.) of a diet in which the imbalance was corrected, their preference was reversed, but only temporarily. The fact that the sensory properties of the imbalanced and corrected diets were very similar suggests that (a) the S associated a beneficial effect with ingestion of the corrected diet; (b) S did not immediately thereafter recognize the imbalanced diet as a novel diet; and (c) subsequently, ingestion of the imbalanced diet was associated with an undesirable effect and aversion to the imbalanced diet again developed. (25 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of lateral hypothalamic lesions on food intake of rats during exposure to cold.

Two experiments investigated the feeding behavior of 41 male Sprague-Dawley rats with lateral hypothalamic (LH) lesions and 13 Ss with chemical lesions of central dopaminergic neurons. LH damage impaired both physiological and behavioral responses of Ss during exposure to a 5°C environment. The LH-lesioned Ss usually did not conserve heat in the cold as well as did controls (n?=?13), nor did they always increase their caloric intake to meet their energy needs. However, when given sucrose solution to drink instead of water, LH-lesioned Ss increased their ingestion of chow in response to cold exposure. It is likely that the elevated consumption of palatable fluid served to relieve dehydration and thereby removed its constraints on eating, thus permitting hyperphagia to occur. In contrast to these results, Ss with large dopamine-depleting brain lesions, produced by intraventricular 6-hydroxydopamine treatments, always increased food intake when exposed to cold stress and demonstrated no apparent problems in peripheral vasoconstriction. Thus, it is unlikely that striatal dopamine depletions account for either the impaired feeding response or the inadequate heat conservation of rats with lateral hypothalamic lesions during cold stress. (33 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of prenatal exposure to N-methylpyrrolidone on postnatal development and behavior in rats

Pregnant rats (Mol:WIST) were exposed to 150 ppm N-methylpyrrolidone for 6 hours per day on gestation days 7-20. The dose level was selected so as not to induce maternal toxicity or decrease viability of offspring. In the preweaning period, the exposed offspring had a lower body weight and their physical development was delayed. Neurobehavioral evaluation of the male pups revealed no effects on basal functions of the central nervous system. The animals appeared normal and motor function (rotarod), activity level (open field), and performance in learning tasks with a low grade of complexity were similar in the two groups. However, in more difficult tasks such as the reversal procedure in Morris water maze and operant delayed spatial alternation (Skinner boxes), performance was impaired in exposed offspring.     

Effects of probability mode on preference reversal.

Estimated verbally and numerically the chances that specific events will occur using 6 analysts. 60 decision makers used each type of estimate to make binary-choice decisions and to bid for lotteries based on the events. The usual reversal of preference between choice and bidding procedures was found in the numerical condition, but the frequency of preference reversals was significantly reduced in the verbal condition. This reduction occurred because risk aversion was reduced in choice when verbal estimates were given, whereas bidding was unaffected by presentation mode. The pattern of results was predicted by and supports the hypothesis that the relative importance given to the dimensions of a prospect depends on the form in which the information is displayed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of lead exposure on licking and yawning behaviour in rats

Most studies on facial trauma in the pediatric age group focus on special subgroups. This investigation encompasses all traumatic facial injuries, minor and major, of children and adolescents. Epidemiological data of the type and pattern of injury of trauma patients less than 19 years of age, treated during a 3-year-period in a large metropolitan trauma centre were reevaluated. Of the 1385 patients, 68% had soft tissue injuries, 24% had dental trauma, and 8% fractures of facial bones. More than 90% suffered from minimal or minor trauma. The leading cause of injury was a fall, predominantly at the toddler stage. In adolescents an adult mechanism of trauma prevailed: over 60% of injuries were sequelae of an assault or altercation. The male sex predominated through all age groups and for all types of injuries. The bulk of soft tissue injuries are located within a small falling zone, extending from the nose to the mental area. There was a rising incidence of fractures of facial bones towards older age groups, mandibular fractures being the most common. Condylar fractures, with their potential impact on further growth of the mandible, are seen frequently in children and adolescents, making up 80% of the fractures of the lower jaw.     

Operant investigation of mating preference in female rats.

Permitted 4 female Long-Evans hooded rats to indicate preferred mating partners by giving them operant control over the choice of a pair of sexually active males. Pressing 1 of 2 levers released 1 of the pair of male rats which was then allowed a single sexual contact. It was possible for a female to establish a preference in less than 10 estrous matings. No preference was apparent during diestrus tests, but preference returned when the female was again placed in estrus. When the males released by the levers were rotated in the apparatus, those females showing a preference altered their behavior accordingly. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Odor preference and urine-marking scales in male and female rats: Effects of gonadectomy and sexual experience on responses to conspecific odors.

Investigation and urine-marking responses of 112 male and female Long-Evans rats toward conspecific urine odors were recorded in pair-wise comparison tests. Each of 16 S groups was given 15 preference tests, 1 for each of the possible pairs of 5 urine odors and a no-odor control (N). The urine sources were own group (G), intact male (M), castrated male (Mc), ovariectomized female (Fo), and estrous females (F). Results were scaled by using a technique based on L. L. Thurstone's (1927) law of comparative judgment. Intact males with sexual experience ordered their odor preferences N?     

Music-induced context preference following cocaine conditioning in rats.

Traditional models of drug-seeking behavior have shown that exposure to associated environmental cues can trigger relapse. These learned associations take place during repeated drug administration, resulting in conditioned reinforcement. Although considerable investigation has occurred regarding simple conditioned stimuli, less is known about complex environmental cues, particularly those that may be salient in human addiction. Recent studies indicate that music can serve as a contextual conditioned stimulus in rats and influence drug-seeking behavior during abstinence. The purpose of the present study was to further assess the effectiveness of music as a conditioned stimulus in rats, to determine rats' preferences for two contrasting pieces of music, and to determine rats' preferences for music versus silence. To this end, we created an apparatus that gave instrumental control of musical choice (Miles Davis vs. Beethoven) to the rats themselves. After determining baseline musical preference, animals were conditioned with cocaine (10 mg/kg) to the music they initially preferred least, with alternating conditioning sessions pairing saline with the music preferred most. The animals were subsequently tested in a drug-free state to determine what effect this conditioning had on musical preference. The results indicate that music serves as an effective contextual conditioned stimulus, significantly increasing both musical preference and locomotor activity after repeated cocaine conditioning. Furthermore, we found that rats initially favor silence over music, but that this preference can be altered as a result of cocaine-paired conditioning. These findings demonstrate that, after repeated association with reward (cocaine), music can engender a conditioned context preference in rats; these findings are consistent with other evidence showing that musical contextual cues can reinstate drug-seeking behavior in rats. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Effects of prolonged exposure to morphine and methadone on in vivo parameters of immune function in rats

In rats, two 6-week repeated dose oral toxicity studies were performed with morphine (250 and 500 mg/kg food) and methadone (200 and 400 mg/kg food), respectively. Alterations in immune function were studied by assessing primary and secondary immune responses to sheep red blood cells. In addition, the ability to resist challenge with infectious agents was measured in host resistance models employing the parasite Trichinella spiralis and the bacterium Listeria monocytogenes. The primary and secondary antibody responses to sheep red blood cells were not affected by treatment with either morphine or methadone. The clearance of L. monocytogenes bacteria in the spleen was not affected either. Prolonged treatment with morphine, however, resulted in a decrease in host resistance to T. spiralis infection, as indicated by a 1.5-fold increase in numbers of muscle larvae counted in the carcass, but did not affect the T. spiralis-specific IgM, IgG and IgE antibody responses. In contrast to morphine, the methadone-treated animals did not show a significant change in host resistance to T. spiralis. Total serum IgG levels, however, were increased in high-dose methadone-treated animals. Apparently, prolonged administration of morphine to rats resulted in immune suppression, mediating a slight, though biologically relevant, exacerbation of the T. spiralis infection, whereas methadone did not.     

Effects of acute inhalation exposure to isoamyl nitrite on the hypothalamo-pituitary-adrenal axis in male Sprague-Dawley rats

Isoamyl nitrite (IAN) is a member of the family of volatile organic nitrites that exert vasodilatory effects and have recently exhibited a considerable potential for inhalation abuse. In an effort to provide mechanistic insight into the neurotoxic effects and abuse potential of these agents, the present study was designed to evaluate the acute effects of IAN on the hypothalamo-pituitary-adrenal (HPA) axis. Attempts were also made to correlate the neuroendocrine effects of IAN with its pharmacokinetic profile. Male Sprague-Dawley rats were exposed to 600 or 1200 ppm IAN by inhalation for 10 or 30 min. Following exposure, adrenocorticotropic hormone (ACTH) and corticosterone in plasma and corticotropin-releasing factor (CRF) in three brain regions (hypothalamus, hippocampus, and frontal cortex) were determined by radioimmunoassay. Levels of IAN in the three brain regions as well as in blood were measured by gas chromatography to determine the target tissue concentrations responsible for neuroendocrine changes. Uptake of IAN into blood and all brain regions was very rapid, as stable concentrations were achieved within 10 min of exposure and maintained for 30 min of continuous inhalation. Plasma corticosterone decreased significantly after 10 min inhalation of both IAN doses, and returned to control levels after 30 min. Moreover, plasma ACTH was significantly increased by 10 and 30 min of exposure to 600 and 1200 ppm IAN, while hypothalamic CRF increased significantly after 30 min of exposure to the 600 ppm dose. These latter findings suggest activation of the hypothalamus and pituitary due to a reduction in negative feedback resulting from the initial decrease in corticosterone. Although plasma ACTH was greatly increased after 30 min, plasma corticosterone levels were unchanged, indicating that IAN primarily acts to inhibit the synthesis or secretion of adrenal steroids and that activation of the HPA axis is not involved in the behavioral manifestations of IAN inhalation. These compensatory effects of HPA axis regulation, and possibly the vasodilatory properties of IAN, also likely precluded the establishment of definitive relationships between observed changes in hormone levels and blood or regional brain concentrations of the inhalant.     

Effects of different levels of integration on advertising preference and intention to purchase.

90 black and 90 white male undergraduates evaluated 6 proposed advertisements in terms of attractiveness and likelihood of purchase of the product advertised. The advertisements differed in the degree of racial integration depicted, which was operationally defined by a 5-point continuum ranging from 0 whites and 4 blacks (0W-4B) to 4 whites and 0 blacks (4W-0B). The hypothesis that young blacks react negatively to integrated ads depicting tokenism (e.g., 3 whites to 1 black) and positively to ads depicting equality (e.g., 2 whites to 2 blacks) was supported with each of the dependent measures. (20 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of response restriction during exposure to inescapable shock upon subsequent one-way and shuttle-avoidance performance in rats.

Investigated the effects of signaled inescapable shock on subsequent avoidance performance in 3 experiments with male Holtzman rats (N = 188). Exp I indicated that prior shock exposure (PSE) facilitated 1-way and shuttle avoidance. When Ss were preshocked in a harness so that free mobility was not possible, the facilitative effects of PSE on shuttle, but not 1-way avoidance performance, were largely reduced. Exp II indicated that activity during CS periods following PSE was greater among unrestrained than restrained Ss. Exp III showed that immobilization via injection of succinylcholine chloride did not affect the facilitative effects of PSE relative to that of Ss preshocked in a harness. Results are interpreted in terms of response repertoire changes produced by PSE in conjunction with the response requirement of the avoidance task. (French summary) (17 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Intermittent exposure of medulloblastoma cells to topotecan produces growth inhibition equivalent to continuous exposure

Camptothecin analogues such as topotecan increase the number of covalent topoisomerase I-DNA complexes, which, in turn, have been proposed to initiate apoptosis. If induction of apoptosis by the camptothecins is, in fact, dependent on the formation of topoisomerase I-DNA complexes, then it would be of clinical relevance to identify schedules of exposure to the camptothecins that maximize the formation of these complexes but minimize the total amount of the drug administered. The time and dose dependence of topoisomerase I-DNA complex formation was determined by incubating Daoy pediatric medulloblastoma cells in vitro with topotecan at concentrations equivalent to those achievable in the plasma clinically (10, 50, or 200 nM) and measuring the number of complexes present in cells incubated for 15 min to 48 h with the drug. Regardless of the concentration of topotecan used, covalent topoisomerase I-DNA complexes were maximal within 15 min following addition of the lactone form of topotecan to the tissue culture medium. After 2 h of exposure to topotecan, complexes had decreased from maximum to approximately half of that value. Few, if any, complexes were detectable with topotecan incubations of 24-48 h. Growth inhibition studies showed that the IC50s of topotecan for the Daoy cell line (2.2 x 10(-9) M) and also for a second pediatric medulloblastoma cell line, SJ-Med3 (3.6 x 10(-9) M), exposed to topotecan 8 h daily for 5 days or continuous exposure were equivalent. The decrease in topoisomerase I-DNA complexes between 15 min and 1 h was consistent with a pH-dependent re-equilibration of topotecan to the less active hydroxyacid form of the drug. The decrease in complexes after a 2-48-h incubation with the drug was attributable neither to biological inactivation of topotecan as shown by sequential growth inhibition studies nor to a decrease in amount of topoisomerase I in the drug-treated cells. Indirect immunofluorescence labeling of topoisomerase I in Daoy cells incubated for 48 h with 10 nM topotecan showed a redistribution of nucleolar topoisomerase I. We are currently evaluating the antitumor effect of intermittent repetitive exposures to topotecan in mice bearing Daoy cells as a xenograft. The clinical utility of each effective schedule of exposure will depend on whether the therapeutic index of repetitive intermittent exposure to the drug is more or less favorable than the therapeutic index of continuous exposure.     

Effects of failure to meet client preference in a counseling interview analogue.

The hypothesis that failure to meet client preference for high- or low-directive counselor style would adversely affect interpersonal process was tested with 48 undergraduates in a counseling intervention analog oriented around students' actual problems. Students with strongly stated preferences for high- or low-directive counselors were randomly assigned to a counselor whose style was congruent or incongruent with their preference. The Therapist Behavior Scale was used to assess counselor directiveness. Dependent variables included 3 speech and 2 satisfaction measures. The data do not support the hypothesis. There was no evidence that failure to meet client preference adversely affected interview process. Clients of high-directive counselors expressed significantly greater satisfaction with the client–counselor relationship, spent only about 50% as much time per utterance, responded significantly more quickly, and exhibited less silence time while they held the floor than did clients of low-directive counselors. Results suggest that recent interest in ascertaining and meeting client preference may not be relevant to the quality of the interpersonal process. (35 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of maternal exposure to chlorinated diphenyl ethers on thyroid hormone concentrations in maternal and juvenile rats

Polychlorinated diphenyl ethers (PCDEs) are industrial byproducts and widespread environmental contaminants. Their structural similarity to PCBs suggests that they may exhibit subtle effects on both adult and juvenile mammals. We examined the effects of 3 PCDEs (2,2',4,5,6'-pentachlorodiphenyl ether, 2',3,4,6'-tetrachlorodiphenyl ether, and 2,2',4,4',5,5'-hexachlorodiphenyl ether) on maternal rat thyroid levels shortly after exposure, and on the thyroid levels of 16 day old juvenile rats that had been prenatally exposed. Both 2,2',4,5, 6'-pentachlorodiphenyl ether and 2',3,4,6'-tetrachlorodiphenyl ether depressed thyroxine (T4) levels in the maternal females as well as in both sexes of juvenile rats. 2,2',4,4',5,5'-hexachlorodiphenyl ether did not alter T4 levels in the pregnant females, but depressed juvenile T4 levels. None of the congeners studied significantly altered T3 levels. Effects on thyroid hormones did not correlate with the congeners' induction of cytochrome P450.