Stimulus intensity in sensory preconditioning of rats.

Examined the sensory preconditioning (SPC) analogs to UCS and CS intensity in 2 experiments with male hooded rats (N= 144). In Exp. I, Ss received S1-S2 (light and tone, counterbalanced) pairings with 1 of 3 different intensities of S2, followed by conditioned emotional response (CER) training to S2. Suppression of drinking by S1 (SPC groups) and S2 (CER groups) was tested. Amount of SPC was not significantly affected by S2 intensity, but the strength of the CER was an increasing function of S2 (CS) intensity. In Exp. II, amount of SPC was a monotonically increasing function of S1 intensity. Results are interpreted in terms of the similarities and differences between SPC and classical conditioning. (French summary) (16 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Cross-cultural personality correlates of intensity and content category of positive experiences.

Investigated the relationship between teenagers' personality traits and 2 aspects of their most positive remembered experiences (MPREs)—intensity and content—across cultures expected to differ on these variables. 192 male and 159 female Israeli Arabs, 166 male and 191 female Israeli Jews, and 195 male and 191 female US Christians (aged 14–15 yrs) completed a high school personality questionnaire (HSPQ) and a positive experience questionnaire (PEQ). MPREs elicited by the PEQ were rated on a 4-point intensity scale and then classified as with external world, with self, or interpersonal. Results indicate that, despite cultural differences in mean intensities and content-category distributions, 9 of the HSPQs' 14 personality factors correlated (beyond the effect of culture) with either intensity, content category, or both. Content categories exhibited sharply differentiated personality factor tendencies. Intensity-linked personality factor tendencies seemed consistent with self-actualizer characteristics described by A. H. Maslow (1971). (46 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Leukocyte-endothelial adherence correlates with pancreatic nitric oxide production in early cerulein-induced pancreatitis in rats

The authors retrospectively investigated the long-term visual recovery in 32 macular reattached eyes that had been monitored for more than 5 years after surgery. The best corrected visual acuities were better at 5 years postoperatively than at 3 months by two lines or more in 17 eyes (53%). In these 17 eyes, visual acuities continued to improve for up to 10 years after surgery. In the other 15 eyes, the visual acuities remained within one line of the 3-month values. Improvement of the long-term postoperative visual acuity was found to be statistically correlated with younger age, no or mild myopia (>-5 diopters), and shorter duration of macular detachment (< or =30 days). Surgeons should be aware that the visual function of reattached retinas may continue to improve over the long term, especially when these beneficial factors are present.     

Free-operant avoidance behavior in rats with lateral septal lesions: Effect of shock intensity

The purpose of experiment 1 was to examine the relationship between shock intensity and normal rats' free-operant (Sidman) avoidance performance on a 3-component, multiple schedule. The results showed an inverted U-shaped relation between response rate and shock intensity, but no consistent relation between shock rate and shock intensity was found. Experiment 2 showed that lateral sptal lesions produced a bidirectional change in reactivity to electric shock. An increased reactivity was observed in the initial sessions starting on the 11th day after the surgery, while a reduced reactivity was observed in the final sessions when stable performance had been reacquired. These changes were not a function of the waning of general hyperreactivity with post-operative recovery: the septal lesions in this study did not produce any "sham rage". From 40 to 80% of the variance in response rates was accounted for by this bidirectional change in the reactivity to shock.     

Septal correlates of conditioned inhibition and excitation in rats.

Recorded multiple-unit activity in the lateral septum of rats during Pavlovian differential conditioning. In Exp I, 14 male Sprague-Dawley rats received a classical aversive discrimination paradigm, while 11 Ss were presented with a control procedure in which the UCS (shocks) was administered randomly with regard to the CS. Septal unit activity increased during presentations of the conditioned inhibitor and was markedly suppressed during presentations of the conditioned excitor in the conditioning-group Ss and not in controls. Baseline activity remained unchanged in the conditioning group but was suppressed in the random control group. Furthermore, termination of the aversive stimuli was marked by a burst of firing in the conditioning group, but no such rebound was seen in the control group. In Exp II (6 Ss), a classical appetitive discrimination paradigm was given, in which septal unit activity increased in the presence of the conditioned excitor and was suppressed in the presence of the conditioned inhibitor. Results indicate a role for the septum in the relief of aversive states. (16 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Autonomic and behavioral correlates of appetitive conditioning in rats.

The cardiac responses accompanying conditioned stimulus (CS)-generated (orienting) and unconditioned stimulus (US)-generated appetitively motivated behaviors (P. C. Holland, 1977) were investigated. On the basis of contemporary psychophysiological research, CS-generated responses were predicted to produce bradycardia, and US-generated responses to produce tachycardia. Pairing a 10-s visual CS with food delivery produced conditioned behavioral orienting (rearing) during the initial portion of the CS, followed by magazine approach (US-generated) responses as the CS progressed. CS onset produced a decrease in heart rate, mediated by an increase in parasympathetic stimulation of the heart, which persisted throughout the 10-s CS; no support for a biphasic cardiac response was observed. These data are discussed with respect to other conditioned autonomic responses and their relevance to foraging and food ingestion. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Macrophage inflammatory protein-1beta induces dexamethasone-unresponsive fever in rats

It has been hypothesized that endogenous glucocorticoids represent an important negative feedback system involved in the modulation of cytokine-induced fever through the inhibition of prostaglandins (PG) production in the preoptic anterior hypothalamus (AH/POA). The purpose of this study was to determinate whether glucocorticoids modulate the PG-independent febrile response induced by macrophage inflammatory protein-1beta (MIP-1beta) in a manner similar to other pyrogenic cytokines. Subcutaneous pretreatment with dexamethasone (1, 2 and 4 mg/kg; 1 h) had no effect on fever induced by microinjection of 50 pg MIP-1beta into the rat's AH/POA. It is demonstrated for the first time that, unlike other cytokines, fever induced by MIP-1beta is independent of glucocorticoid modulation. Finally, these results offer new perspectives about the pathogenesis of glucocorticoid-unresponsive pyrexia.     

Stimulus intensity modulates associative and nonassociative responding in preweanling rats

The purpose of the present study was to determine whether preweanling rats respond differentially to the intensity and energy source of a stimulus. Previous studies have suggested that infants process compound stimuli based on net stimulus intensity regardless of the energy source of the compound's elements, but more direct tests have been needed of the infant's response to the stimulus attributes of intensity and energy source. This response was tested for auditory and visual stimuli that had been equated (Experiment 1) in terms of perceived intensity (low and high). Intensity level and energy source of the stimuli were varied independently within nonassociative (Experiment 2) and associative (Experiment 3) procedures. The overall results indicate that stimuli of a low-perceived intensity were processed in terms of their intensity, whereas high-intensity stimuli were processed on the basis of energy source. These results are relevant to contemporary issues of cognitive development in humans and animals.     

Response to angiotensin inhibition in rats with sustained renovascular hypertension correlates with response to removing renal artery stenosis

In this paper we present a resource-explicit Donor-Receiver model for reciprocally altruistic interactions that obeys the defining inequalities of the Prisoner's Dilemma. In our model, individuals vary in the quantity of resource they invest when cooperating (termed "generosity") and they have the freedom to opt out of interactions with potential partners on the basis of their past experiences with these players (termed "choosiness"). Dynamic optimal solutions were found using a genetic algorithm in which the decision rules (cooperate or defect), generosity when cooperating, and choosiness exhibited by individuals when deciding to opt out, were all coded on genes held on two separate chromosomes. Through this genetic algorithm, individuals that had alleles which resulted in greatest success at playing our modified Prisoner's Dilemma left more offspring. When the benefit of receiving a unit resource exceeded the cost of giving, then generous cooperative behaviour tended to emerge within the population, even when the alleles of all the individuals in the starting population were set to defect. When the probability of individuals re-encountering one another was increased, individuals not only cooperated more, but they developed greater generosity. However, as the ratio of the benefits received to costs expended increased above 1, individuals in this model remained highly cooperative but their median generosity decreased significantly. In contrast to earlier studies using genetic algorithms, the extra potential for cheating afforded by asymmetrical degrees of generosity meant that genuinely cooperative behaviour did not emerge in the equivalent round-robin tournament in which individuals were not able to exercise partner preference.     

Loss of hippocampal CA1 pyramidal neurons correlates with memory impairment in rats with ischemic or neurotoxin lesions.

Rats were trained for 20 days in a modified T maze to perform an invariant, tactile discrimination and a variable, delayed spatial discrimination, and then were exposed either to 30 min of transient forebrain ischemia or to low- or high-dose ibotenic acid to damage the dorsal hippocampus bilaterally. Only rats exposed to ischemia or high-dose ibotenic acid demonstrated impaired performance during 30 postoperative test days on both aspects of the task (p?p?     

Lipopolysaccharide induces fever and decreases tail flick latency in awake rats

In humans, somatic aches and pains are frequently reported during fever. To determine whether exogenous pyrogen administration increases nociceptive responsiveness in rats, the tail flick reflex evoked by noxious heat was compared in animals that received an intraperitoneal injection of exogenous pyrogen (lipopolysaccharide) or vehicle (saline). There were no differences in skin temperature between lipopolysaccharide- and vehicle-injected rats. Awake rats injected with lipopolysaccharide exhibited an increase in colonic temperature and a decrease in tail flick latency when compared to vehicle-injected rats. Neural events that trigger fever may therefore also modulate nociceptive responsiveness.     

Telomerase activity correlates with growth of transplantable osteosarcomas in rats treated with cis-diammine dichloroplatinum or the angiogenesis inhibitor AGM-1470

To determine the role of telomerase activity in the growth of tumors in rats undergoing chemotherapy, a comparison of the volumes of telomerase-positive transplantable osteosarcomas was made in rats treated with the antineoplastic agent cis-diammine dichloroplatinum (CDDP) or the angiogenesis inhibitor O-(chloroacetylcarbamoyl)fumagillol (AGM-1470). Male F344 rats, 8 weeks old, received transplants of macroscopic lung metastatic nodules into the subcutaneous back space and treatment was started on day 14 thereafter. CDDP was injected i.v. at doses of 0, 0.625, 1.25 and 2.5 mg/kg body weight (b.w.) and AGM-1470 was administered at total doses of 0, 2.5, 5 and 10 mg/kg b.w. over 2 weeks by osmotic pumps, also implanted into the subcutaneous back space, but remote from the transplanted tumors. On day 28, all animals were killed for measurement of transplanted tumor size and determination of telomerase activities by telomeric repeat amplification protocol (TRAP) assay. The results showed telomerase activity to be highly correlated with the treated/non-treated (T/C) tumor size ratio (r = 0.96, P < 0.0001). In a second experiment, CDDP at 2.5 mg/kg b.w. and AGM-1470 at 10 mg/kg b.w., these being the most effective doses, were given as in the first experiment, and animals were serially killed on days 14, 21, 28, 35 and 42. Tumors in rats treated with CDDP and AGM-1470 showed 18.2% and 20.5% of the control telomerase activity on days 35 and 21, respectively, when tumor growth was inhibited. However, on day 42, the activities increased to 46.5% and 92.5%, this correlating with re-growth (r = 0.73, P < 0.0001). These results suggest that decline of telomerase activity may be involved in tumor growth retardation induced by chemotherapeutic agents. This possibility clearly warrants further mechanistic studies.     

Perceived intensity of peripheral thermal stimuli is independent of internal body temperature

Four adult male human subjects were tested under three conditions of internal body temperature: hypothermia, normal, and hyperthermia. Under each of these conditions, they judged the intensity (degree of warmness or coolness) and the hedonic quality (degree of pleasantness or unpleasantness) of a series of stimuli ranging from hot to cold. The results showed that whereas hedonic quality is greatly influenced by the value of internal body temperature, the perception of warmness or coolness is independent of internal temperature and dependent only on peripheral stimulation.     

Effect of stressor intensity on habituation and sensitization of glucocorticoid responses in rats.

Studied the effect of stressor intensity on habituation/sensitization of the adrenocortical stress response (ASR) in rats. When lower intensity shock was given, the response first habituated to no-shock control levels but later returned to the same magnitude as seen on the 1st probe day. Plasma corticosterone responses given higher intensity shock never habituated and instead demonstrated an increased response indicative of sensitization. Responsiveness to exogenous adrenocorticotropin 24 hr after the last stress session was monotonically related to the intensity of the stressor presented during the experimental sessions. Data are consistent with the rule from habituation literature that stimulus intensity is inversely related to the magnitude of habituation and extend the dual process theory of P. M. Groves and R. F. Thompson (see record 1971-02046-001) to an endocrine respondent. The data also suggest that an explanation as to the discrepancies in the literature concerning ASR to repeated presentation of stressors may relate to differences in the stressor parameters used. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Chemokine-induced fever: intracerebroventricular actions of MIP-1 and MIP-1 alpha in rats

The central pyrogenic actions in the rat of doublet macrophage inflammatory protein-1 (MIP-1) and MIP-1 alpha were determined by their intracerebroventricular infusion. Doses of 560 pg and 11.2 ng of MIP-1 or 10.0 ng MIP-1 alpha infused into the third cerebral ventricle induced a long lasting fever. However, MIP-1 alpha was much less potent than MIP-1 in terms of intensity and longer latency. Overall, these cytokines are pyrogenic when acting on the walls of the third ventricle; however, a dose 10 times greater than that injected directly into the anterior hypothalamus is required to evoke fever, as based on earlier experiments. Finally, circulating MIP-1 could act centrally by its entry through the choroid plexus into the ventricular system of the brain.     

Phase response curves to ambient temperature pulses in rats

The effect of pulses of warm ambient temperature on the phase of activity onset in Long-Evans hooded rats, Rattus norvegicus, free-running in constant light was examined. In two experiments, rats were exposed to pulses reaching a maximum of 34 degrees C or 32 degrees C. Phase response curves were obtained with advances occurring mainly in the subjective day, and delays mainly, but not entirely, in the subjective night. Significant negative correlations between rhythm period and phase-shifts were found. There were no consistent relationships between changes in activity levels due to the temperature pulses and phase-shifts. Cycles of higher and lower ambient temperature may entrain circadian activity rhythms in mammals by daily advance or delay phase-shifts.