Gradual increase in cutaneous threshold induced by repeated hypnosis of healthy individuals and patients with atopic eczema

Gradual increase in cutaneous pain threshold was found in healthy subjects and patients with atopic eczema during repeated hypnotic sessions with specific suggestions. This increase was less in the former than in the latter group. Repeated threshold measurements did not influence the threshold. The analgesic effect outlasted the hypnotic sessions by several months. It could be, however, suddenly reduced by appropriate hypnotic suggestion.     

Conditioned ethanol aversion in rats induced by voluntary wheel running,forced swimming,and electric shock: An implication for aversion therapy of alcoholism

This study was planned to demonstrate rats’ acquisition of aversion to ethanol solution consumed before voluntary running, forced swimming, or electric shock delivery. Wistar rats under water deprivation were allotted to four groups of eight rats each, and all rats were allowed to drink 5% ethanol solution for 15 min. Immediately after the ethanol drinking, rats of Group Run were put into the individual running wheels for 15 min, those of Group Swim were put into the individual swimming pools for 15 min, those of Group Shock received electric shocks for 15 min (15 0.45-mA shocks of 0.7s with the intershock interval of 1 min) in the individual small chambers, and those of Group Control were directly returned back to the home cages. This procedure was repeated for six days, followed by a two-day choice test of ethanol aversion where a bottle containing 5% ethanol solution and a bottle of tap water were simultaneously presented for 15 min. In the test, Groups Run, Swim, and Shock drank ethanol solution significantly less than tap water, while Group Control drank both fluids equally. The effects of running, swimming, and shock were equivalent. The successful demonstration of acquired ethanol aversion induced by exercise (running and swimming) or shock in rats suggests an avenue for clinical application of exercise and shock treatments for human alcoholics, though there are many issues to be resolved before the practical use.     

The occurrence of an increase in correlation by restriction of range

Given three variables,x, y, z, univariate selection onx, usually reduces the correlationr _{y z} . However, in some cases, whenr _{x y} orr _{x z} assumes extreme values,r _{y z} may increase. This reversal is explained by comparison to the effects of suppressor variables and predictors of predictability.     

The enhancement of retention induced by vasopressin in mice may be mediated by an activation of central nicotinic cholinergic mechanisms.

Immediate post-training subcutaneous administration of lysine vasopressin (LVP, 0.003-1.00 microgram/kg) enhanced retention, whereas the vasopressin antagonist AAVP (0.01-0.30 microgram/kg) impaired it, in male Swiss mice tested 48 h after training in an inhibitory avoidance task. Both effects were dose-dependent. Neither LVP nor AAVP affected response latencies in mice not given the footshock on the training trial. The simultaneous administration of AAVP at a dose (0.01 microgram/kg) which had no effect on retention shifted the dose-response curve of LVP to the right. Nicotine (1.0-30.0 micrograms/kg, sc), a central nicotinic cholinergic agonist, also facilitated retention in a dose-related manner without affecting the retention performance of unshocked mice. The effect of nicotine was prevented by the central acting nicotinic cholinergic receptor antagonist mecamylamine (5 mg/kg, sc.). In contrast, neither hexamethonium (5 mg/kg, sc), a peripheral acting nicotinic receptor blocker, nor atropine (0.5 mg/kg, sc) or methylatropine (0.5 mg/kg, sc), two anticholinergic drugs which are known to act on muscarinic cholinergic receptors, prevented the effect of post-training nicotine. The effects of LVP and nicotine were time-dependent, suggesting that both treatments enhanced retention by influencing post-training processes involved in memory storage. Low doses of nicotine (1.50 microgram/kg, sc) or the central anticholinesterase physostigmine (35 micrograms/kg, sc) and LVP (0.003 microgram/kg, sc), which had no effect on retention when administered alone, produced a synergistic interaction when given together following training. The influence of LVP (0.03 microgram/kg, sc) on retention was prevented not only by AAVP (0.01 microgram/kg, sc) but also by mecamylamine (5 mg/kg, sc), whereas the effects of nicotine (10.0 micrograms/kg, sc) were prevented only by mecamylamine. These results suggest that the enhancement of retention induced by vasopressin is probably due to an activation of central nicotinic cholinergic mechanisms which are critical for memory formation.     

Effect of a novel experience prior to training or testing on retention of an inhibitory avoidance response in mice: involvement of an opioid system

These experiments examined the effects of a novel experience prior to training or retention testing on 24-h retention of an inhibitory avoidance response in mice. The experiments were based on previous evidence that novel training experiences release hypothalamic beta-endorphin. When given 1 h prior to training, the novel experience (clinging to the wire-mesh ceiling and exploring a small box) attenuated the memory-enhancing effects of post-training administration of naloxone as well as the enhancing effects of beta-endorphin administered prior to the retention test. The novel experience given prior to training did not block the enhancing effects of post-training administration of epinephrine. beta-Endorphin and the novel experience both enhanced retention performance when administered 1 h (as well as 3 but not 6 h) prior to the retention test. The enhancement found with both treatments was blocked by simultaneous administration of naloxone or by administration of propranolol a few minutes prior to the retention test. The findings of these experiments are consistent with the view that the effects of the novel experience are due to a release of endogenous beta-endorphin and provide additional evidence that the effects, on retention, of naloxone given post-training and beta-endorphin given prior to a retention test, are based on training-induced release of beta-endorphin.     

Facilitation of extinction by an increase or a decrease in trial duration

Five experiments examined the effects of altering the duration of a conditioned stimulus (CS) for extinction. For the first 3 experiments, rats received conditioning with a 10-s CS before different groups received extinction with a CS that was either the same duration or longer than that used for conditioning. For the remaining 2 experiments, conditioning was conducted with a 60-s CS before different groups received extinction with a CS of either the same duration or a shorter duration than that used for conditioning. In all experiments, extinction progressed more readily when the CS duration was different for the 2 stages than when it was constant. The results are discussed in terms of rate expectancy theory and associative learning theory.     

Mecamylamine prevents the enhancement of retention induced by lysine vasopressin in mice

Lysine vasopressin (0.03 microgram/kg, sc) enhanced retention of a one-trial, step-through inhibitory avoidance task when injected into male Swiss mice immediately post-training, as indicated by retention performance 48 h later. A low dose of the vasopressin antagonist, AAVP (0.01 microgram/kg, sc), did not significantly affect retention, whereas a higher dose (0.03 microgram/kg, sc) impaired retention. Neither lysine vasopressin nor AAVP modified latencies to step-through of mice that had not received a footshock during training. The simultaneous injection of AAVP (0.01 microgram/kg, sc) prevented the enhancement of retention induced by lysine vasopressin. The influence of lysine vasopressin on retention was antagonized by the simultaneous administration of mecamylamine (5 mg/kg, sc) but not by hexamethonium (5 mg/kg, sc), atropine (0.5 mg/kg, sc), or methylatropine (0.5 mg/kg, sc). A modulatory role of vasopressin on the activity of central cholinergic nicotinic mechanisms which participate in memory formation is suggested.     

Priming word order by thematic roles: No evidence for an additional involvement of phrase structure

Three experiments are reported that studied the priming of word order in German. Experiment 1 demonstrated priming of the order of case-marked verb arguments. However, order of noun phrases and order of thematic roles were confounded. In Experiment 2, we therefore aimed at disentangling the impact of these two possible factors. By using primes that differed from targets in phrase structure but were parallel with regard to the order of thematic roles, we nevertheless found priming demonstrating the critical impact of thematic roles. Experiment 3 replicated the priming effects from Experiments 1 and 2 within participants and revealed no evidence for a modulation of priming by phrase structure. Consequently, our findings suggest that word order priming crucially depends on the structural outline of thematic roles rather than on the linearization of phrases.     

Hormonal and behavioural abnormalities induced by stress in utero: an animal model for depression

Prenatal stress in rats can exert profound influence on the off spring's development, inducing abnormalities such as increased "anxiety", "emotionality" or "depression-like" behaviours.Prenatal stress has long-term effects on the development of the hypothalamo-pituitary-adrenal(HPA) axis and forebrain cholinergic systems. These long-term neuroendocrinological effects are mediated, at least in part, by stress-induced maternal corticosterone increase during pregnancy and stress-induced maternal anxiety during the postnatal period. We have shown a significant phase advance in the circadian rhythms of corticosterone secretion and locomotor activity in prenatally-stressed (PNS) rats. When subjected to an abrupt shift in the light-dark(LD) cycle, PNS rats resynchronized their activity rhythm more slowly than control rats. In view of the data suggesting abnormalities in the circadian timing system in these animals, we have investigated the effects of prenatal stress on the sleep-wake cycle in adult male rats. PNS rats exhibited various changes in sleep-wake parameters, including a dramatic increase in the amount of paradoxical sleep. Taken together, our results indicate that prenatal stress can induce increased responses to stress and abnormal circadian rhythms and sleep in adult rats.Various clinical observations in humans suggest a possible pathophysiological link between depression and disturbances in circadian rhythmicity. Circadian abnormalities in depression can be related to those found in PNS rats. Interestingly, we have recently shown that the increased immobility in the forced swimming test observed in PNS rats can be corrected by chronic treatment with the antidepressant tianeptine, or with melatonin or S23478, a melatonin agonist. Those results reinforce the idea of the usefulness of PNS rats as an appropriate animal model to study human depression and support a new antidepressant-like effect of melatonin and the melatonin agonist S23478.     

Changes in brain activation induced by the training of hypothesis generation skills: an fMRI study

The aim of the present study is to investigate the learning-related changes in brain activation induced by the training of hypothesis generation skills regarding biological phenomena. Eighteen undergraduate participants were scanned twice with functional magnetic resonance imaging (fMRI) before and after training over a period of 2 months. The experimental group underwent eight biological hypothesis generation training programs, but the control group was not given any during the 2-month period. The results showed that the left frontal gyri, the cingulate gyrus, and the cuneus were activated during hypothesis generation. In addition, the brain activation of the trained group increased in the left inferior and the superior frontal gyri, which are related to working memory load and higher-order inferential processes. However, the activation after training decreased in the occipito-parietal route, which is associated with the perception and the analysis processes of visual information. Furthermore, the results have suggested that the dorsolateral prefrontal cortex (DLPFC) region is the critical area in the training of hypothesis generation skills.     

Effects of anandamide and morphine combinations on memory consolidation in cd1 mice: involvement of dopaminergic mechanisms

In the present research the interaction between the endogenous ligand for the cannabinoid CB1 receptor anandamide (arachidonylethanolamide) and morphine in memory consolidation was investigated. Four sets of experiments were carried out with CD1 mice tested in a one-trial inhibitory avoidance task. The drugs were administered intraperitoneally after training of the animals in the apparatus. In the first set of experiments morphine (0.3 or 0.5, but not 0.15mg/kg) or anandamide (3 or 6 but not 1.5mg/kg) dose-dependently impaired memory consolidation. In the second set of experiments the administration of an otherwise ineffective dose of anandamide (1.5mg/kg) enhanced the memory impairment exerted by morphine (0.3 and 0.5mg/kg) when the drugs were injected immediately after training. In the third set of experiments the combined treatments of anandamide (1.5mg/kg) and morphine (0.5mg/kg) 2h after training were ineffective showing that the effects observed on performance following immediate posttraining administration of anandamide and morphine combinations were reflecting direct influences on memory consolidation. In the fourth set of experiments otherwise ineffective doses of the D1 DA receptor agonist SKF 38393 or the D2 DA receptor agonist LY 171555 antagonized the memory impairment produced by anandamide and morphine in combination, suggesting a possible involvement of dopaminergic mechanisms.     

Cyclophosphamide impairs hippocampus-dependent learning and memory in adult mice: Possible involvement of hippocampal neurogenesis in chemotherapy-induced memory deficits

Cyclophosphamide (CYP) is an anti-neoplastic agent as well as an immunosuppressive agent. In order to elucidate the alteration in adult hippocampal function following acute CYP treatment, hippocampus-related behavioral dysfunction and changes in adult hippocampal neurogenesis in CYP-treated (intraperitoneally, 40 mg/kg) mice (8–10-week-old ICR) were analyzed using hippocampus-dependent learning and memory tasks (passive avoidance and object recognition memory test) and immunohistochemical markers of neurogenesis (Ki-67 and doublecortin (DCX)). Compared to the vehicle-treated controls, mice trained at 12 h after CYP injection showed significant memory deficits in passive avoidance and the object recognition memory test. The number of Ki-67- and DCX-positive cells began to decrease significantly at 12 h post-injection, reaching the lowest level at 24 h after CYP injection; however, this reverted gradually to the vehicle-treated control level between 2 and 10 days. We suggest that the administration of a chemotherapeutic agent in adult mice interrupts hippocampal functions, including learning and memory, possibly through the suppression of hippocampal neurogenesis.     

When bonuses backfire: an inaction inertia analysis of procrastination induced by a missed opportunity

An inaction inertia analysis of procrastination was used to generate the prediction that using bonuses to encourage early task completion will have two opposing effects, encouraging early task completion by some but also inducing procrastination for those who miss the bonus. Study 1 showed that the addition of bonuses for early completion produced both of these effects and also led to overall task completion rates that were either equal to (large bonus) or actually less than (medium and small bonuses) those obtained by simply establishing a completion deadline with no bonus. In Study 2, a lottery methodology was used to manipulate the size of a missed bonus for all participants. Even under these conditions of reduced personal responsibility the larger missed bonus led to increased procrastination as predicted by the inaction inertia analysis. Possible mediating processes based on anticipated regret and perceived fairness were discussed. Copyright © 2007 John Wiley & Sons, Ltd.     

Effects of MK-801 and ethanol combinations on memory consolidation in CD1 mice: involvement of GABAergic mechanisms

In the present research the effect of the noncompetitive N-methyl-d-aspartate receptor antagonist MK-801 and ethanol combinations on memory consolidation and the involvement of GABAergic mechanisms in this effect were investigated in CD1 mice injected intraperitoneally with the drugs immediately or 120 min after training in a one-trial inhibitory avoidance apparatus and tested for retention 24 h later. The results showed that (a) the retention performances of mice were impaired in a dose-dependent manner by immediate posttraining MK-801 (0.2 and 0.3, but not 0.1 mg/kg) and ethanol (1 and 2, but not 0.5 g/kg) administrations; (b) an otherwise ineffective dose of MK-801 (0.1 mg/kg) enhanced the deleterious effect exerted by ethanol (1 and 2 g/kg); (c) an otherwise ineffective dose of muscimol (0.5 mg/kg) enhanced, while otherwise ineffective doses of picrotoxin (0.25 mg/kg) or bicuculline (0.1 mg/kg) antagonized, this effect; and (d) no effect was observed when the treatments were carried out 120 min after training, suggesting that the effects observed following immediate posttraining administrations were due to the influence on the consolidation of memory. From these experiments it is evident that (a) MK-801 enhances ethanol's effects on memory consolidation and (b) GABAergic mechanisms are involved in this effect.     

The durations of hippocampal and cortical cholinergic activation induced by spatial discrimination testing of mice in an eight-arm radial maze decrease as a function of acquisition

Sodium-dependent high-affinity choline uptake velocities in P2 fractions of the hippocampus and cortex of mice were analyzed at different times following both the first (Day 1) and last (Day 9) daily sessions of a spatial discrimination testing procedure in an eight-arm radial maze. Results showed that the immediate (30 s) post-training increase in mean hippocampal and cortical cholinergic activity observed on Day 1 did not significantly vary over days despite a marked and progressive improvement of discrimination performance. In contrast, the duration of these activations was considerably shortened in both structures between Days 1 (more than 1 hr) and 9 (about 15 min). The possible involvement of these changes in memory consolidation processes is discussed.     

The impairment of retention induced by pentylenetetrazol in mice may be mediated by a release of opioid peptides in the brain

Pentylenetetrazol (PTZ, 45 mg/kg, ip) impaired retention of a one-trial step-through inhibitory avoidance task when injected into male Swiss mice 10 min after training, as indicated by retention performance 48 h later. The amnestic effect of PTZ was prevented by naltrexone (0.01 or 0.10 mg/kg, ip) administered after training, but prior to PTZ-treatment. On the contrary, neither naltrexone methyl bromide (0.01, 0.10, or 10.0 mg/kg, ip), a quaternarium analog of naltrexone, nor MR2266 (0.01 or 0.10 mg/kg, ip), a putative kappa opiate receptor antagonist, modified the behavioral effects of PTZ. On the other hand, the body seizures produced by PTZ were unaffected by any of the three opiate receptor antagonists that were given before the convulsant. Taken together, these results suggest that the effects of PTZ on retention are mediated, at least in part, by opioid peptides of central origin, and rules out a possible participation of opioid peptides derived from prodynorphin-precursor molecule. Administration of beta-endorphin (0.01 or 0.10 microgram/kg, ip) 10 min prior to testing attenuate the retrograde amnesia caused by PTZ. The effect of beta-endorphin was prevented by the simultaneous administration of naltrexone (0.10 mg/kg, ip) prior to testing. Naltrexone has no effect of its own upon retrieval. These results suggest that the impairment of retention induced by PTZ is probably due, at least in part, to a release of opioid peptides in the brain during the post-training period. PTZ given after training do not affect consolidation or memory storage, as mice thus treated may retrieve the learned information when they are submitted to an appropriate neurohumoral and/or hormonal state in the test session, that is, beta-endorphin injection. Therefore, the action of PTZ would be primarily at the level of the mechanism that make stored information available for late retrieval.     

Sex-dependent changes induced by prenatal stress in cortical and hippocampal morphology and behaviour in rats: an update

Recent prospective studies have shown that gestational stress in humans is more likely to cause cognitive and emotional problems in the offspring if it occurs during weeks 12-20 of pregnancy. There are also suggestions that such problems may be gender dependent. This review describes recent studies that found sex differences in the behaviour and brain morphology of rats stressed prenatally during the equivalent period of neuronal development in humans. Learning deficits are more prevalent in males and anxious behaviour in females but their appearance depends also on the timing and intensity of the stress and the age when the offspring were tested. Cognitive deficits and anxiety are linked to a sex-dependent reduction in neurogenesis and in measures of dendritic morphology in the prefrontal cortex and hippocampal formation. Maternal adrenalectomy prior to the stress prevents the anxiety in both sexes and learning deficits in males. Corticosterone administration to the dam to mimic levels induced by stress reinstates only the anxiety, indicating that it arises from foetal exposure to corticosterone from the maternal circulation. Learning deficits in males may result from a combination of a reduction in testosterone and in aromatase activity, together with the action of other adrenal hormones.     

Conflict resolution in two-digit number processing: evidence of an inhibitory mechanism

Psychological Research - We investigated the mechanism involved in conflict resolution when individuals processed two-digit numbers. Participants performed a comparison task in blocks of two...