Amygdala kindling-resistant (SLOW) or -prone (FAST) rat strains show differential fear responses

The authors compared two rat strains, selectively bred for their susceptibility to amygdala kindling, with respect to their performance on various behavioral and learning tasks that are associated with fear and anxiety. The two rat strains differed significantly in measurements of exploration of novel and familiar environments, as well as in reactivity to footshock and fear-based learning. The kindling-resistant (SLOW) strain exhibited a lower ratio of open- to closed-arm entries in the elevated plus-maze, less activity over days in the open field, greater behavioral suppression in the open-field if previously footshocked, greater freezing in the inhibitory avoidance task, and slower acquisition and poorer retention in the one-way avoidance task than did the kindling-prone (FAST) strain. These experiments suggest that the SLOW rats are more expressively fearful than the FAST rats, particularly with respect to environmentally triggered freezing or immobility. Further, these observations imply that the relatively constrained excitability of the amygdala network in the SLOW rats might mediate their relatively greater expression of fear and anxiety compared with the FAST rats.     

Application of flagella-based immunoassays for serologic detection of Salmonella pullorum infection in chickens

Behavior of two rat strains was analyzed with and without 1-week pretest handling. Male rats (150-200 g body weight) of the strains PVG/OlaHsd (PVG) and Hsd:Sprague-DawleySD (SPRD) were tested once in a standard open field and an enriched open field and twice in an elevated plus-maze. Behavioral analysis revealed significant differences between the two strains and differential effects of the pretest handling procedure. SPRD rats displayed higher levels of activity and exploratory behavior than the PVG rats, whereas PVG rats were obviously less anxious. One-week pretest handling had an "anxiolytic" effect and changed activity and exploration-related behavior of the animals in both strains. Activity-related parameters were mainly affected in SPRD rats and anxiety-related ones in PVG rats. The data give evidence that differences in behavior of rats are not only determined genetically but also by preceding handling procedures. Because the two rat strains responded differentially to the pretest handling, we recommend to use a well-defined handling procedure before starting a behavioral test, especially when drug applications are included.     

Developmental factors modify stress ulcer incidence in a stress-susceptible rat strain

Our multifactor theory of stress ulcer assumes that environmental factors that operate during early growth stages influence the elaboration of stress ulcer in adult rats. The theory would predict that rats exposed to either neonatal handling, or raised in a stimulus enriched environment, would reveal differences in stress ulcer susceptibility. In study 1, some Wistar rats and ulcer-susceptible Wistar Kyoto (WKY) rats were handled daily from birth to day 21, whereas other rats from each strain were not disturbed. In study 2, Wistar and WKY rats were raised (3 months) in a large stimulus-dense enriched environment, whereas other rats from each strain were raised in standard rat cages where visual and auditory stimuli were minimized. At 3 months all rats were observed in the open field test (OFT), a test of emotionality, as well as the Porsolt forced swim test (FST), a test of behavioral depression, and subsequently exposed to the ulcerogenic water restraint procedure. Neonatal handling produced results suggesting increased wall climbing activity in the FST, reduced response latency in the OFT, increased body weight and reduced ulcer severity, but these differences were not significant. Rearing in an enriched environment produced similar results but these difference were more pronounced and significant in the Wistar rats as compared to the WKY rats. Thus early environmental manipulations can influence adult behavior and the elaboration of stress ulcer disease, but the impact of these manipulations is less salient in an organism with an endogenous susceptibility to the disease.     

Anxiety-related behaviors in the elevated zero-maze are affected by genetic factors and retinal degeneration.

Anxiety levels were tested in an elevated zero-maze for 8 inbred strains of mice that are used widely in biomedical and behavioral research. Strain differences were observed for activity, latency to enter an open quadrant, open time, and defecation, demonstrating that genetic factors mediate anxiety in this paradigm. Three of the strains have the rdl mutation that causes retinal degeneration and were less anxious in the maze. To discern whether visual acuity is a source of difference on the maze, anxiety levels were tested in a congenic strain in which the rdl allele has been replaced with the wild-type allele. The congenic strain, with normal vision, had higher levels of anxiety. This study provides baseline data for the selection and use of any of these strains in pharmacological challenges in the maze, and provides a starting point of the identification of strains that may have appropriate backgrounds for targeted mutation studies. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Strain comparisons of DFP neurotoxicity in rats

The purpose of this study was to assess intraspecies differences in behavioral and autonomic function in three strains of rat following administration of diisopropyl fluorophosphate (DFP), an irreversible inhibitor of acetylcholinesterase activity. Male rats of the Long-Evans (LE), Fischer 344 (F344), and Sprague-Dawley (SD) strains wer administered DFP at doses of 0-1.5 mg/kg (sc). The animals were placed 60 min later into one of two motor activity chambers and tested for 30 min. Motor activity was measured using either a Doppler-based system or a commercial photocell device. Following measurement of motor activity in the Doppler system, body temperature (Tb) was measured and blood was then withdrawn by cardiac puncture and analyzed for serum cholinesterase activity (ChE). The remaining rats were retested 1 d after DFP administration in the photocell device. The results showed a significant influence of strain on the effects of DFP. Motor activity of LE rats was reduced by DFP at doses of 1.0 and 1.5 mg/kg, whereas the activity of F344 rats was reduced only at 1.5 mg/kg. The relative sensitivity of SD rats depended on the device used to measure motor activity. The SD rats resembled F344 rats in their response to DFP when motor activity was measured in the photocell device, and LE rats when motor activity was measured in the Doppler system. The Tb of F344 rats was unaffected by DFP, while the LE and SD rats became hypothermic at 1.5 mg/kg. The DFP-induced inhibition of serum ChE activity was significantly less in F344 rats. All three strains retested the day after DFP still showed significant decreases in motor activity. Overall, it appears that the F344 strain is relatively resistant to the behavioral and autonomic effects of DFP. This intraspecies variability should be considered in selecting appropriate experimental models for assessing the neurotoxicological hazards of cholinesterase-inhibiting pesticides.     

Effects of cholinomimetics, cholinolytics and atypical antidepressants in the behavioral despair test in the rat

The effect of some cholinolytics, cholinomimetics and atypical antidepressants on behavior of rats forced to swim (in the "behavioral despair test") was investigated. In addition, the relation between the test performance and the inborn level of exploratory and locomotor activities was studied. Cholinomimetics prolonged, while cholinolytics and antidepressants shortened the immobility phase ("despair reaction"). The "despair reaction" was less pronounced in rats with high motor exploratory activity level.     

Sensitivity to onset and rhyme does predict young Children's reading: a comment on Muter, Hulme, Snowling, and Taylor (1997)

Muter, Hulme, Snowling, and Taylor (1997) claimed that measures of phoneme segmentation, and not measures of rhyme, predict young children's reading. They base this claim on the relative predictive success of two rhyme and two phoneme segmentation tasks. However, there is a problem with one of their two rhyme measures, the Rhyme Detection measure. The children were asked to select a choice word which "rhymes with or sounds like" a target word, but the authors only scored rhyme choices ("boat"-"coat") as correct. Choices of words with the same onset as the target ("train"-"tractor") were counted as mistakes, even though these latter choices also shared a common sound with the target. A better way to score the task is to count onset as well as rhyme choices as correct. The new score predicts reading and spelling as well as the phoneme tasks. This result is consistent with the hypothesis of Goswami and Bryant (1990) that sensitivity to onset and rhyme, as well as awareness of phonemes, plays a part in children's success in reading and to spelling.     

Paradoxical giving up and the reduction of sleep performance anxiety in chronic insomniacs.

Paradoxical intention has been shown to improve sleep performance in chronic insomniacs, presumably by interrupting their overly anxious sleep efforts. It was hypothesized that instructions to simply give up such sleep intentions—without trying to stay awake—could have a similar effect. Giving-up instructions framed as a paradoxical sleep-improvement method ("try giving up") were compared with giving up presented as a way to improve nighttime comfort and morning restedness without any sleep improvement ("give up trying"), along with a placebo-attention (self-monitoring) treatment. The 3 treatments were embodied in a printed booklet delivered by mail and evenly distributed among 33 20–56 yr old chronic insomniacs recruited from the general community. All 3 treatment groups improved in daily sleep estimates ("sleep efficiency") after treatment, but only the giving-up groups improved on a self-report measure of sleep performance anxiety. It is suggested that such a reduction in performance anxiety may be an important therapeutic outcome, with or without sleep improvement. (43 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Sex differences in perceived accuracy of falsified personality inventory feedback.

80 college freshmen who scored near the mean on the Extraversion (E) and Neuroticism (N) scales of the Eysenck Personality Inventory were given falsified score reports stating that the Ss were either high E or low E and either high N or low N. Ss receiving low-E ("introverted") reports tended to rate the efficiency of the instrument and the accuracy of the report less favorably than did those receiving high-E reports. Females receiving low-E reports tended to make ratings signficantly lower than did males receiving low-E reports. Ss receiving high-N ("neurotic") reports rated the inventory less favorably than did those receiving low-N ("stable") reports. The lowest average ratings were made by females receiving low-E and high-N reports. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Not all rat strains are equal: Differential unconditioned fear responses to the synthetic fox odor 2,4,5-trimethylthiazoline in three outbred rat strains.

Predator odors induce unconditioned fear in rats; however, the synthetic predator odor 2,4,5-trimethylthiazoline (TMT) either elicits robust fear behavior (e.g., freezing) or no fear responses at all. The authors investigated whether this is due to the use of different outbred rat strains. TMT induced robust freezing in Sprague-Dawley and Long-Evans rats but not in Wistar rats. All 3 strains avoided TMT, but Wistar rats were less sensitive to TMT. Wistar rats are capable of freezing; all 3 strains displayed the same amount of odor-cue conditioned freezing. Thus, TMT is a robust unconditioned fear stimulus in rats, and prior negative results from other laboratories were due to the choice of a rat strain (Wistar) that is less responsive to TMT. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Sensitization of salt appetite is associated with increased "wanting" but not "liking" of a salt reward in the sodium-deplete rat.

To examine the role of incentive sensitization in the potentiation of salt appetite by prior depletions, the authors assessed the motivation to obtain salt ("wanting") and the palatability of salt ("liking") independently in salt-sensitized rats. Breakpoint on a progressive ratio reinforcement schedule was used to measure salt wanting and taste reactivity was used to measure salt liking in rats with and without a history of Na+ depletion. Salt-sensitized rats displayed higher breakpoints relative to controls. However, a history of Na+ depletion was not associated with a greater positive shift in taste reactivity measures. The data suggest that these components of reward are separable in this model and support the general proposition that sensitization may alter wanting but not liking. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Brain corticotropin-releasing factor immunoreactivity and receptors in five inbred rat strains: relationship to forced swimming behaviour

In the present work we studied the relationship between behaviour in the forced swimming test (FST), a test that presumably measures depressive-like behaviour in rodents, and central corticotropin-releasing factor (CRF) concentration and binding in five strains of rats. The strains were: Brown-Norway (BN), Fisher (FIS) 344, Lewis (LEW), spontaneously hypertensive rats (SHR) and Wistar-Kyoto rats (WKY). The FST data corresponding to the pretest showed significant inter-strain differences in both struggling and immobility: BN and WKY rats displayed lower levels of struggling and longer periods of immobility, LEW and SHR rats showed intermediate levels, and FIS rats were the most active. The results of the pretest were roughly similar to those observed in the test, the activity of WKY being extremely low. The CRF binding revealed significant inter-strain differences in prefrontal cortex and hippocampus, but not in cerebellum, pons-medulla or hypothalamus: in the prefrontal cortex, BN and FIS rats showed greater CRF binding than LEW, SHR and WKY rats; in the hippocampus BN rats showed higher levels of CRF binding than the other strains. The study of CRF content in various brain areas revealed inter-strain differences in prefrontal cortex and pons-medulla, but not in parietal-temporal cortex or in hypothalamus (CRF concentrations in the hippocampus were not detectable): CRF content in the prefrontal cortex was higher in BN than in the other strains, although the differences with FIS were not statistically significant; in the pons-medulla, FIS and LEW showed significantly higher CRF content than the other strains. From the present results it appears that BN and WKY rats were more prone to adopt passive strategies in the FST, but they did not show higher brain CRF immunoreactivity or down-regulation of CRF receptors. Hence, although there were inter-strains differences in all variables studied, no evidence for a relationship between the FST behaviour and central CRF activity was found.     

Bacterial gene products in response to near-ultraviolet radiation

Skilled forelimb use was examined in five different rat strains (DA/Ztm, LEW/Ztm-ci, LEW.1W/Ztm, SD/Ztm, SPRD/Ztm-Cu3) by means of the 'staircase test', as originally described by Montoya et al. [20] (C.P. Montoya, H.L. Campbell, K.D. Pemberton, S.B. Dunnett, The 'staircase test': A measure of independent forelimb reaching and grasping abilities in rats, J. Neurosci. Methods 36 (1991) 219-228). Strain-dependent differences were observed most prominently during the acquisition phase, and less pronounced, at the full performance level. SD/Ztm and DA/Ztm rat strains seemed to be particularly skilled in their forelimb use, although with varying levels of activity. Interestingly, significant differences in skilled forelimb movements were found between the related Sprague-Dawley derived and Lewis congenic rat strains. No clear-cut correlation was found between skilled forelimb use and basic nutrition-dependent measures, such as pretest body weight or weightloss during the test period. Based on previous observations on strain-dependent behavioral variations it seems likely that the differences in skilled forelimb use, as observed in the present study, might be caused by morphological and/or functional strain-dependent alterations in the involved neuronal circuitries, such as motor cortex, caudate-putamen unit and mesotelencephalic dopamine system. However, they should also be considered as potentially influencing parameters in studies related to the behavioral effects of lesions and restorative therapies in the central nervous system.     

Diffusion-weighted MR microscopy with fast spin-echo

A diffusion-weighted fast spin-echo (FSE) imaging sequence for high-field MR microscopy was developed and experimentally validated in a phantom and in a live rat. Pulsed diffusion gradients were executed before and after the initial 180 degrees pulse in the FSE pulse train. This produced diffusion-related reductions in image signal intensity corresponding to gradient ("b") factors between 1.80 and 1352 s/mm2. The degree of diffusion weighting was demonstrated to be independent of echo train length for experiments using trains up to 16 echoes long. Quantitative measurements on a phantom and on a live rat produced diffusion coefficients consistent with literature values. Importantly, the eight- to 16-fold increase in imaging efficiency with FSE was not accompanied by a significant loss of spatial resolution or contrast. This permits acquisition of in vivo three-dimensional data in time periods that are appropriate for evolving biological processes. The combination of accurate diffusion weighting and high spatial resolution provided by FSE makes the technique particularly useful for MR microscopy.     

The Effect of Age of Acquisition in Visual Word Processing: Further Evidence for the Semantic Hypothesis.

The authors investigated whether the meaning of visually presented words is activated faster for early-acquired words than for late-acquired words. They addressed the issue using the semantic Simon paradigm. In this paradigm, participants are instructed to decide whether a stimulus word is printed in uppercase or lowercase letters. However, they have to respond with a verbal label ("living" or "nonliving") that is either congruent with the meaning of the word (e.g., saying "living" to the stimulus DOG) or incongruent (e.g., saying "nonliving" to the stimulus dog). Results showed a significant congruency effect that was stronger for early-acquired words than for late-acquired words. The authors conclude that the age of acquisition is an important variable in the activation of the meaning of visually presented words. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A children's social desirability questionnaire.

A Children's Social Desirability (CSD) questionnaire was constructed and administered to 956 Ss in Grades 3, 4, 5, 6, 8, 10, and 12. A direct question ("yes-no") form of the scale was presented to children in the 3rd, 4th, and 5th grades in individual testing sessions, and a true-false form was given older Ss in group sessions. For both forms of the questionnaire, split-half reliabilities and test-retest (1-month interval) reliabilities were high. Socially desirable responses were more frequently given by younger children than by older children, by dull Ss than by bright Ss, by girls than by boys, and by Negro children than by white children. Social class, size of family, and ordinal position were not associated with CSD responses. Questions were raised pertaining to the generality of this response and pertaining to the premises on which this measure of social desirability, as well as that of Crowne and Marlowe, is based. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Genetics of alcoholism: rapid development of a new high-ethanol-preferring (HEP) strain of female and male rats

A genetically based animal model of alcoholism has been developed in a relatively short period of 3 years. The new strain is characterized by an intense preference for ethanol over water as well as unique behavioral, neurochemical and other attributes. This new strain, termed high-ethanol-preferring (HEP) rats, was derived initially from selective cross-breeding of a variant strain of female Harlan Sprague-Dawley (SD) rats with the outbred Wistar line of male ethanol-preferring (P) rats. In this study, drinking patterns of both genders were obtained over 10 days by presenting water and ethanol in concentrations ranging from 3% to 30%. To expedite the development of the new strain, only three to five female and male rats served as breeders, which were chosen from all litters on the basis of their maximum g/kg intake integrated with proportion of ethanol to total fluid values. Profiles of intake of preferred concentrations of ethanol were obtained over 24 h of unlimited access as well as during 2-h intervals of limited access to ethanol. Levels of blood ethanol were measured in both female and male HEP animals during bouts of ethanol drinking in the limited access paradigm. By the sixth generation of HEP rats, ethanol consumption of the females often exceeded that of any other rat genetically bred to drink ethanol (e.g., at a concentration of 15.7%, 10.3 g/kg per day). Seven additional characteristics are notable: 1) the HEP rats prefer ethanol in the presence of a nutritious chocolate drink or nonnutrient sweetened solution (aspartame); 2) high levels of blood ethanol are associated with their drinking; 3) females drink significantly greater g/kg amounts of ethanol than HEP males and prefer a higher percent concentration of ethanol; 4) the drinking of ethanol by the female HEP animals does not fluctuate during the estrous cycle; 5) neurochemical assays show differential profiles of 5-HT, dopamine, and their metabolites in different regions of the brain; 6) measures of activity using the elevated plus maze, open field, and cork gnawing reveal differences between genders of HEP rats and SD rats; and 7) the HEP animals are without phenotypically expressed abnormalities. Finally, one cardinal principle derived from this study revealed that the breeding strategy to develop high-ethanol-drinking rats centers on the use of multiple solutions of ethanol whereby the intakes of ethanol in concentration of 9% through 20% dictate the ultimate selection of breeding pairs over successive F generations. Further, it is concluded that because of an intense rise in ethanol drinking of the F1 generation of female HEP rats well above that of the parental SD female breeders, the complex genotypic characteristic of the male P rat is predominantly responsible for evoking ethanol drinking in female offspring.     

Ruling out postnatal origins to attention-deficit/hyperactivity disorder (ADHD)-like behaviors in a seizure-prone rat strain.

Adult Fast (seizure-prone) and Slow (seizure-resistant) kindling rat strains exhibit divergent behaviors in paradigms relevant to attention-deficit/hyperactivity disorder (ADHD) in humans. Similar dissociations in rodent behavior have been linked to disparities in early life experience, suggesting that differential maternal care or postnatal interactions may underlie these behaviors. Consequently, the authors compared maternal behavior and preweaning pup weights in these 2 strains under control and cross-fostered conditions and examined its effects on subsequent adult offspring behavior. Ultimately, several distinct maternal behaviors were apparent between the 2 strains under control conditions, and some of those behaviors were then malleable by pup condition. Yet, in spite of the resultant complex maternal patterns across groups, all offspring showed behavioral phenotypes akin to their genetic strain. Thus, a specific postnatal environment is unlikely to underwrite ADHD-like behaviors in the seizure-prone Fast rats, which implicates a genetic or prenatal origin for the ADHD phenotype. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The Maudsley reactive and nonreactive strains: a North American perspective

The Maudsley experiment involving bidirectional selection for differences in open-field defecation (OFD) is briefly reviewed. Attention is focused on the North American stocks of these strains since problems have been encountered with regard to the open-field behavior and continued viability of the British stocks. The open-field behavior of the colonies of the Maudsley strains at the National Institutes of Health and at the University of Northern Iowa closely resembles that originally exhibited by the British strains, provided they are compared under standard conditions. On more complex behaviors, such as escape-avoidance conditioning, serious discrepancies have emerged between the British and North American findings. These may be resolved when attempts are made to replicate more closely the procedures used in the British studies. Particular emphasis has been placed on the potential of a second nonreactive strain, the MNRA/HAR strain, to serve as a replicate of selection for decreased emotionality. The value of the RXNRA group of recombinant-inbred strains, developed and maintained by the author, for examining the reliability of associations between traits is also stressed. A correlation between OFD and biochemical aspects of sympathetic function has been found in the Maudsley strains. This finding lends credibility to Hall's claim that the expression of emotionality is linked to autonomic arousal.     

"Effects of optimism, pessimism, and trait anxiety on ambulatory blood pressure and mood during everyday life": Correction to R?ikk?nen et al. (1999).

Reports an error in the original article by K. R?ikk?nen et al (Journal of Personality and Social Psychology, 1999, 76(1), 104–113). Table 4 on page 111 contained an error. The 4 sets of column heads ("Adjusted" and "Unadjusted") were inadvertently transposed. The corrected table is provided. (The following abstract of this article originally appeared in record 1999-00166-008): This study tested whether dispositional measures of optimism, pessimism, and anxiety affected ambulatory blood pressure (BP) and mood and whether any cardiovascular effects of dispositions were moderated by mood. Pessimistic and anxious adults had higher BP levels and felt more negative and less positive than did optimists or low anxious adults throughout the monitoring. The few times that optimists did feel negative were associated with levels of BP as high as those observed among pessimists or anxious individuals, regardless of their mood. To the extent that trait anxiety measures neuroticism, these findings suggest that neuroticism is directly related to health indicators rather than simply to illness behavior. Furthermore, the results suggest that pessimism has broad physiological and psychological consequences. (PsycINFO Database Record (c) 2010 APA, all rights reserved)