Phenotyping of glutathione S-transferase M1 in the Estonian population by ELISA using GSTM1a and GSTM1b specific monoclonal antibodies

We examined the effects of stimulation on either postnatal days 1-7 or 21-27 on passive avoidance reaction (PAR) of young rats. Animals received tactile or visual stimulation for 10 min each day, and were trained on postnatal day 28 in a step-through apparatus using a footshock of 0.75 mA for 2 s. Retention was tested on five consecutive days beginning on day 29. Memory retention was measured for each rat 24, 48, 72, 96 and 120 h after the acquisition trial. Step-through latencies to enter the dark compartment, time spent in the illuminated compartment and number of crossings of the light beam were recorded up to 200 s. Rats that received tactile or visual stimulation during the 4th postnatal week displayed significantly lower PAR latencies, a shorter stay in the illuminated compartment and a higher number of crossings of the light beam compared to rats treated during the 1st postnatal week. The untreated control group showed a rapid decline of PAR latencies. All experimental groups remained in the illuminated compartment longer and showed PAR latencies well above those of the control group. The differences became more pronounced when visual stimulation in the first postnatal week was used. The number of crossings of the light beam was significantly reduced by the treatment, with the exception of the experimental group stimulated visually in the 4th week. The behavioural changes induced by tactile or visual stimulation have a long-lasting effect in coping with a stressful task.     

Passive avoidance behavior in rats after electroconvulsive shock: Facilitative effect of response retardation.

In 3 experiments, a total of 178 male Wistar rats were trained in a one-trial passive avoidance task and then were submitted to electroconvulsive shock (ECS) or to sham ECS. 24 hrs later they were tested for retention, with the door opened either immediately or 30 sec after the beginning of the test. Ss initially forced to avoid for 30 sec continued to avoid for the entire test, but the others had the usual low step-through latencies seen with ECS-treated Ss. Activity measures for those Ss stepping through differentiated groups having received footshock from those not having footshock and ECS. A retest 5-10 min later showed "recovery" in the amnestic Ss and continued avoidance behavior for those that avoided on the first test. Results are taken as evidence that ECS effects are not on memory storage but on the capacity of the animal to organize information effectively and quickly in order to produce an adaptive response. (20 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The noradrenergic system of the amygdala and aversive information processing.

In 4 experiments, 113 water-deprived male Long-Evans rats were trained to drink in a passive avoidance apparatus. After reaching a latency criterion, Ss were given a single 3-sec, 3-mA footshock. Immediately or 12 hrs after footshock, Ss were given intracranial injections of vehicular saline, norepinephrine (NE), propranolol, or dopamine (DA) into the amygdala, internal capsule, lateral ventricles, or caudate-putamen. Ss were tested for passive avoidance at 30 min or 24 hrs following footshock. No memory deficits were seen as a consequence of short-term retention or because of proactive or toxicity effects. Retention deficits were seen in the 24-hr test only in Ss injected with NE in the amygdala, internal capsule, or lateral ventricles. However, qualitative differences in stress-indicative behaviors were noted in the NE groups and in the DA-amygdala Ss. Results suggest that the noradrenergic system of the amygdala is involved in the long-term processing of the emotional attributes of aversive information. (66 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Deficient passive and one-way active avoidance acquisition following medial forebrain bundle lesions in rats.

In 3 experiments with 93 Long-Evans male hooded rats, cathodal electrolytic lesions of the medial forebrain bundle (MFB) at posterior hypothalamic levels produced a mild, transient hypodipsia and lowered jump thresholds to footshock. Lesions produced marked deficits in passive avoidance performance in a paradigm that paired discrete, linearly incrementing footshock intensities with contact of a water spout following 48 hrs of water deprivation. Injections of levo-dextro-5-hydroxytryptophan (75 mg g, ip), the immediate metabolic precursor of serotonin, had no effect on the passive avoidance performance of either experimental or operated control Ss. Lesions of the MFB also resulted in deficient acquisition in a 1-trial step-through passive avoidance paradigm not using motivation to drink and caused a severe acquisition deficit in a 1-way active avoidance task. Lesions of the septal nuclei produced lowered jump thresholds but did not affect acquisition in the 1st passive avoidance task. Results are interpreted as indicating a lesion-induced deficiency in fear learning, independent of the serotonergic functions of the MFB. (45 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The opioid/nonopioid nature of stress-induced analgesia and learned helplessness.

Investigated whether the same factors that activate the processes that produce escape interference might also activate processes leading to opioid stress-induced analgesia (SIA). Exposure to a variety of stressors produces a subsequent analgesic reaction that is sometimes opioid in nature (reversed by opiate antagonists and cross-tolerant with morphine) and sometimes nonopioid. In Exp I, 40 male albino rats were subjected to 20 min of intermittent footshock, 3 min of continuous footshock, tailshock on a VI schedule, or confinement only. Ss were given escape/avoidance training 24 hrs later. In Exp II, 36 Ss received SIA with a tail-flick apparatus. In Exp III, 40 Ss received inescapable tailshocks or confinement only. In Exp IV, 24 Ss received 2 sessions of footshock before tail-flick was assessed. Both of the opioids SIA procedures produced a learned helplessness effect as assessed by shuttlebox escape acquisition and an analgesia that was reinstatable 24 hrs later. The nonopioid procedures produced neither a learned helplessness effect nor a reinstatable analgesia. These data implicate the learning of uncontrollability in the activation of opioid systems. (33 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Differential effects of a reminder cue on amnesia induced by stimulation of amygdala and hippocampus.

Examined the effects of a footshock reminder (FSR) in restoring memory after discrete electrical brain stimulation in 119 male Long-Evans rats. Ss received low-level bilateral electrical stimulation of either the amygdala or the hippocampus after training in a 1-trial passive avoidance task. Ss receiving stimulation showed amnesia when tested 24 hrs after training. One hour after the retention test, Ss received an FSR. 23 hrs later in a 2nd retention test, hippocampus-stimulated Ss showed recovery of memory, while amygdala-stimulated Ss did not. Stimulated Ss that did not receive an FSR remained amnesic. In addition, the effects of amygdala and hippocampal stimulation applied after the FSR were examined. On the 2nd retention test, amygdala stimulation disrupted the FSR effect, while hippocampal stimulation had no deleterious effects. Data are interpreted from a memory-attribute point of view that suggests that the amygdala and hippocampus may be differentially involved in the processing of particular attributes of the learning task. (39 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Interaction between memories in the rat: Effect of degree of prior conflicting learning on forgetting after short intervals.

Gave 132 female Sprague-Dawley albino rats 0, 1, criterion, or criterion + 10 trials of passive-avoidance training. Ss were then given active-avoidance training and were tested for retention 3 min., 60 min., or 24 hr. later. Forgetting of active-avoidance learning after 1 or 24 hr. was increased among Ss given prior training on passive avoidance. The magnitude of this lapse in retention was greater among Ss given more prior opportunities to practice passive avoidance. However, retention after 3 min. was unaffected by prior training. Characteristics of memory retrieval may account for these results. (21 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Reversible inactivation of the median raphe nucleus enhances consolidation and retrieval but not acquisition of passive avoidance learning in rats

Involvement of median raphe nucleus (MRN) in acquisition, consolidation and retrieval of passive avoidance (PA) was investigated with functional suppression of this area by lidocaine. Rats carrying a chronically implanted cannula aimed at the MRN were trained on a step-through passive avoidance task and received intra-MRN injection of lidocaine or saline 5 min before training or 5, 90 and 360 min after acquisition trial or 5 min before the retrieval test. Lidocaine MRN inactivation had no effect on PA learning. Lidocaine injected 5 and 90 min after the acquisition trial significantly enhanced avoidance of the dark compartment in comparison with the control group injected with saline. But PA retention was not affected by lidocaine injected 360 min after acquisition or 5 min before training. Retention latency significantly increased, when lidocaine injected 5 min before retrieval test. Step-through latency of naive rats was not affected by MRN blockade. Furthermore, reversible inactivation of MRN did not have a significant effect on locomotor activity. Our results indicate that the MRN contributes to PA consolidation at least until 90 min after acquisition and involves in PA retrieval. It is concluded that functional ablation of the MRN may disrupt the inhibitory actions of MRN projections to sub-cortical circuits participating in PA memorization and retrieval.     

Effects on avoidance performance of vagal stimulation during previous fear conditioning in rats.

Attempted to determine, from experiments on 5 groups of 10 male albino rats each, whether parasympathetic stimulation given coincidentally with electric shock in a fear-conditioning situation would alter later performance on an avoidance conditioning task. 10 Ss were implanted with a small chronic electrode around the cervical vagus. During preconditioning, consisting of 8 trials of tone followed by inescapable shock, 1 group of Ss received stimulation of the vagus at the time foot shock was delivered. During subsequent avoidance conditioning, these Ss performed the avoidance task significantly better than Ss that received the same preconditioning without vagal stimulation and as well as Ss that had received no preconditioning shock trials. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Inhibition of cerebral protein synthesis does not prolong short-term memory.

In 4 experiments, male Swiss-Webster CD-1 mice were given a single sc injection of a cerebral protein synthesis inhibitor, anisomycin (ANI, 1 mg/S), 20 min prior to a single trial of passive avoidance training. Ss demonstrated impaired retention at test given 3 hrs, 6 hrs, 1 day, and 7 days after training. Retention was not significantly different from that of saline controls when tests were given .5 or 1.5 hrs after training. Prolonging inhibition of brain protein synthesis by giving either 1 or 2 additional injections of ANI at 2 hrs or at 2 and 4 hrs after training did not prolong good retention performance. The temporal development of impaired retention in ANI-treated Ss could not be accounted for by drug dosage, duration of protein synthesis inhibition, or nonspecific sickness at test. In contrast to the suggestion that protein synthesis inhibition prolongs short-term memory, these results indicate that short-term memory is not prolonged by antibiotic drugs that inhibit cerebral protein synthesis. All evidence seems consistent with the hypothesis that short-term memory is independent of protein synthesis and that the establishment of long-term memory depends on protein synthesis during or shortly after training. (33 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Subamnesic cycloheximide treatment delays consolidation in mice.

In Exp I, groups of C57 BL/6J mice were given passive avoidance training and then administered different doses of cycloheximide (CYC) immediately, 30 min, or 1 hr after training. Only the highest dose (150 mg/kg) administered immediately or 30 min after training impaired memory when the mice were tested 72 hrs after training. In Exp II, Ss were given a nonamnesic administration of CYC (30 mg/kg) or saline immediately after training and another injection of CYC (15, 30, or 75 mg/kg) or saline 1 hr after training. The combinations of 30 mg/kg?+?30 mg/kg and 30 mg/kg?+?75 mg/kg impaired memory. Exp III demonstrated that brief carbon dioxide anesthetization initiated immediately after training impaired memory. In Exp IV, mice were given either saline or 30 mg/kg CYC immediately after training and then subjected to either air or CO? anesthetization 30 min after training. Only the group given 30 mg/kg CYC?+?CO? was amnesic when tested 72 hrs after training. Results indicate that the administration of a nonamnesic dose of CYC immediately after training renders the memory susceptible to disruption by additional doses of CYC or other amnesic treatments for a longer period of time than normal. It is suggested that CYC delays consolidation and prolongs the labile period of memory formation. (11 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of d-amphetamine and strychnine on cycloheximide- and diethyldithiocarbamate-induced amnesia in mice.

Administered cycloheximide (CXM) sc to groups of C57BL/6J mice 30 min before or immediately after training on a passive avoidance task and tested them 72 hrs later. Some CXM-pretreated groups were given strychnine or dextroamphetamine immediately after training and others were given amphetamine 1 hr after training. Other groups were given diethyldithiocarbamate (DDC) at various times before or after training. Some DDC-pretreated groups were given amphetamine or strychnine as described above for CXM groups. Immediate posttraining administration of 5 mg/kg amphetamine, but not strychnine, prevented amnesia in CXM-pretreated Ss. DDC induced an apparent amnesia when administered from 30 min before training to 3 hrs after training. Posttraining administration of amphetamine or strychnine did not prevent DDC-induced amnesia. Results are discussed in relation to previous suggestions that CXM and DDC-induced amnesia may be the result of a functional impairment of catecholamine neurotransmitter systems by these drugs. (22 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Extinction and retention of a classically conditioned flexor nerve response in acute spinal cat.

Conditioned adult male and female cats by pairing a mild electrical stimulus to the superficial peroneal sensory nerve (CS) with a stronger electrical stimulus to the ankle skin (UCS) of the same leg. Subsequent extinction was produced by presenting CS-alone trials. In Exp I (42 Ss), Ss given massed extinction trials showed response decrements to base levels, but Ss that received distributed extinction trials showed no decrements. In Exp II, .5-, 1-, 2-, 3-, or 4-hr intervals between acquisition and extinction produced no significant differences in the extinction data. In Exp III (20 Ss), Ss received extinction trials immediately or 30 min after acquisition trials, followed by 20 additional extinction trials 30 min later. Data indicated significant acquisition and extinction in the 10- and 20-acquisition trial groups. As in Exp II (35 Ss), varying the interval between acquisition and extinction did not produce any group differences in the extinction data. These results demonstrate that response increases produced by paired trials in the spinal preparation do not decay spontaneously over time and are not caused by sensitization effects. (23 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Unconditioned stress-induced analgesia following exposure to brief footshock.

Four experiments, with 136 male Sprague-Dawley rats, examined the properties of unconditioned analgesia elicited by electric footshock stimuli using UCS parameters typical of aversive conditioning paradigms. In all experiments, analgesia was inferred from the latency to paw lick in response to painful thermal stimulation in the hot-plate assay. In Exp I, Ss exposed to a 1-sec, 2-mA shock UCS showed significantly longer latencies to respond to painful thermal stimulation than nonshocked controls, whereas nonsignificant increases in response latencies were observed with 1-sec shock UCS of either 0.5 or 1.25 mA. In Exp II, Ss exposed to a 2-mA electric shock UCS showed systematic increases in latencies to respond to painful thermal stimulation as the duration of the shock was varied between 0.5 and 2 sec. Exp III showed that this form of shock-induced analgesia was of short temporal duration. Specifically, significant increases in latencies to respond to painful thermal stimulation occurred 30 but not 90 or 300 sec following exposure to shock. Exp IV demonstrated that this form of analgesia was unaffected by pretreatment with the opiate receptor antagonist naloxone HCl in ip dosages of 1, 5, 10, or 20 mg/kg. Finally, there was no evidence showing that environmental stimuli paired with shock presentations acquired the capacity to evoke analgesia as a conditioned response. Implications of shock-induced analgesia for the study of aversive conditioning and behavior are discussed. (26 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

One-trial associative memory in black-capped chickadees.

Black-capped chickadees (Parus atricapillus), birds that store food, inspected feeders in an aviary (1 of which was baited) and returned after a 5-min retention interval to consume the then-hidden food. In Exp 1, Ss quickly learned this task but only if different feeders were used on each trial. In Exp 2, memory for the baited feeder decayed substantially after 24 hrs but not after 30 min. In Exps 3 and 4, there were 4 alternatives to the baited feeder. Ss performed better than chance from the beginning of these experiments. When Ss made errors on their 1st choice, Ss performed better than chance on their 2nd choice. Exp 4 tested the notion that increasing the cost of inspecting the feeders would reduce errors; however, this did not improve performance. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of variations in stimulus similarity and response requirement during pre-shock upon subsequent one-way active avoidance learning.

Describes 2 experiments with 48 adult male Holtzman albino rats, which examine further the stimulus and response conditions under which prior fear conditioning facilitates 1-way active avoidance acquisition. Fear in both experiments was established during passive avoidance training by administering a single 2-sec shock following a cross-through response from a white to a black compartment. Subsequent active avoidance acquisition was facilitated in Exp. I even though the response requirements of the 2 tasks were incompatible. In Exp. II reversed stimulus-shock arrangements existed in the 2 learning tasks. Facilitation of avoidance acquisition as a function of the prior task was again obtained. (French summary) (15 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effect of adrenocorticotropic hormone on conditioned avoidance in rats interpreted as state-dependent learning.

140 male Charles River CD rats were given 1 training trial that was followed 2 days later by 1 test trial in a "step-out" passive avoidance task. Each S was injected with either ACTH or placebo before training and before testing. 4 groups of Ss were used, representing the 4 possible training-testing injection combinations: placebo-placebo, placebo-ACTH, ACTH-placebo, and ACTH-ACTH. ACTH given in testing increased avoidance for subjects that had received ACTH in training and decreased avoidance for those that had received placebo in training. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Mind over matter: Perceived success at psychokinesis.

Four experiments with 212 undergraduates showed that Ss' estimates of success on a psychokinetic (PK) task were independent of actual performance. In Exp I, Ss given a positive introductory set or no set about PK evidenced more illusory control than Ss given a negative set. In Exp II, both degree of general belief in psychic phenomena and the number of practice trials that Ss received influenced performance estimates, with high believers who received 10 practice trials providing the highest estimates and low believers who received 1 practice trial the lowest. In Exp III, Ss actively involved with the PK task judged their performance more positively than passively involved Ss. Exp IV showed that when they were actively involved in the task, Ss with an internal locus of control (Rotter's Internal–External Locus of Control Scale) gave higher estimates of their success than Ss with an external locus of control. When passively involved, internals and externals did not reliably differ in their estimates, but their estimates were lower in those of active/internals. Results support E. J. Langer's illusion-of-control theory and highlight the importance of general psychic belief and locus-of-control orientation in affecting perceived success at a psychic task. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Incubation and Kamin effects in the rat: Changes in activity and reactivity after footshock.

Tested the activity of 40 male hooded rats 2 min, 1 hr, 4 hrs, or 24 hrs after a series of 10 footshocks (FSs). Activity decreased monotonically over time, whereas when FSs were administered during the test, reactivity to these additional FSs was a -shaped function of the interval between the original FSs and the test. It is hypothesized that these activity and reactivity functions were the basis for incubation and Kamin effects, repectively, the determining factor being the presence or absence of FS during testing. In Exp II, an additional 54 Ss received 10 FSs in the start compartment of a 2-compartment box and were returned either 2 min, 1 hr, 4 hrs, or 24 hrs later for 10 1-way active-avoidance trials. The resulting -shaped relearning function paralleled the -shaped reactivity function produced in Exp I by the same regimen of FS, thus confirming the view that time-related changes in reactivity after FS are the basis for the Kamin effect in rats. (17 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Manipulating subjective expectancy through feedback: A laboratory study of the expectancy–performance relationship.

Investigated the form of the expectancy–performance relationship in a laboratory study of the performance of 132 undergraduates on a simple clerical task. As feedback after each of 8 trials, Ss were told that their performance was better, worse, or borderline. Ss recorded their subjective expectancies before each trial. Over all Ss, feedback condition had no impact on performance; but when 39 Ss whose reported expectancy did not match their assigned feedback were eliminated, a strong expectancy–performance relationship emerged. Ss having intermediate expectancy outperformed those whose expectancy was low or high. Examination of the nonbelievers supported the mediating role of cognitive variables in deciding how hard to work at this task. (8 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)