Single-trial Passive Avoidance Task Research Articles

The effect of CA1 dopaminergic system in harmaline-induced amnesia

In the present study, the effects of bilateral injections of dopaminergic drugs into the hippocampal CA1 regions (intra-CA1) on harmaline-induced amnesia were examined in male mice. A one-trial step-down passive avoidance task was used for the assessment of memory retention in adult male mice. Pre-training intra-peritoneal (i.p.) administration of harmaline (1mg/kg) induced impairment of memory retention. Moreover, intra-CA1 administration of dopamine D1 receptor antagonist, SCH23390 (0.02μg/mouse), dopamine D1 receptor agonist, SKF38393 (0.5μg/mouse), dopamine D2 receptor antagonist, sulpiride (1μg/mouse) and dopamine D2 receptor agonist, quinpirole (0.25 and 0.5μg/mouse) suppressed the learning of a single-trial passive avoidance task. Also, pre-training intra-CA1 injection of subthreshold doses of SCH23390 (0.001μg/mouse) or sulpiride (0.25μg/mouse) with the administration of harmaline (1mg/kg, i.p.) reversed impairment of memory formation. However, pre-training intra-CA1 injection of SKF38393 (0.1μg/mouse) or quinpirole (0.1μg/mouse) increased pre-training harmaline (0.25 and 0.5mg/kg, i.p.)-induced retrieval impairment. Moreover, SKF Ca blocker (SKF) (0.01μg/mouse) decrease the amnesia induced by harmaline (1mg/kg), while co-administration of SKF (0.01μg/mouse)/sulpiride (0.25μg/mouse) or SCH23390 (0.001μg/mouse)/sulpiride (0.25μg/mouse) potentiate amnesia caused by harmaline. These findings implicate the involvement of CA1 dopaminergic mechanism in harmaline-induced impairment of memory acquisition.

The roles of RNA synthesis and protein translation during reconsolidation of passive-avoidance learning in the day-old chick

This series of experiments investigated the role of protein translation and RNA synthesis on consolidation and reconsolidation of passive avoidance learning (PAL) in day-old chicks. Although it is well established that protein translation is required after a reminder, there are conflicting reports in the literature concerning the requirement for RNA synthesis at this time. Day-old male New Hampshire × White Leghorn chicks were trained on a single trial passive avoidance task. The results confirmed the requirement for protein translation during reconsolidation with memory deficits induced by anisomycin (ANI) (10 mg/kg) detected at 60 min post-reminder. It was also established that RNA synthesis was required for consolidation of PAL through inhibition by 5,6-Dichloro-1-β-D-ribofuranosylbenzimidazole (DRB) (0.075 µg/kg), administered at or after training. The same dose of DRB was also found to inhibit memory post-reactivation. However injections were required before the reminder trial and memory deficits were evident by 60 min, consistent with that found for ANI post-reminder. As with ANI, the DRB-induced memory deficit post-reminder was also transient, and resolved by 24 h post-reminder. For both reconsolidation drug studies, the memory deficit was wholly dependent on the memory being reactivated by a reminder-trial. The study highlights an important role for RNA synthesis following memory reactivation.

Ouabain does not impair reconsolidation following a reminder of passive avoidance learning in the day-old chick

This study investigated the effect of ouabain, an inhibitor of NA(+) and K(+) ATPase, on consolidation and reconsolidation of a passive avoidance learning task in the day-old chick. In the consolidating trace, ouabain is thought to inhibit an intermediate-term memory phase, some aspects of which acts as a "trigger" for long-term stabilisation of the trace by new protein synthesis. It was hypothesised that a similar process may initiate the protein synthesis observed following reminder-activated reconsolidation in the young chick. Chicks were trained on a single trial passive avoidance task. A dose of 0.2 ug/kg ouabain was administered intracranially either 5 min post-training (consolidation processes) or 5 min post-reminder (reconsolidation processes). Consistent with previous research, ouabain administration induced a memory deficit following the initial learning trial. However, contrary to expectation, ouabain did not disrupt memory processing post-reactivation. This finding provides further evidence for the notion that consolidation and reconsolidation are associated with similar, but distinct, stages of processing.

Polyinosinic:polycytidylic acid induces memory processing deficits in the day-old chick

Anecdotal and experimental evidence has demonstrated that humans and animals exhibit physiological and cognitive alterations in response to sickness and injury. It is now clear that these changes are due to the actions of proinflammatory cytokines. The current study examined the effects of peripheral administration of polyinosinic:polycytidylic acid, a synthetic double-stranded viral RNA, on the memory processes of day-old chicks trained on a single trial passive avoidance task. Polyinosinic:polycytidylic acid impaired performance on the passive avoidance task in a dose-dependent manner. Maximal deficits were observed when 5 g/kg polyinosinic:polycytidylic acid was administered 120 min before training. Tests for retention revealed that interference in memory consolidation appeared between 30 and 40 min after training. These results indicate an inhibitory effect of polyinosinic:polycytidylic acid on the processes of memory formation at the transition from intermediate-term memory phase (A) to intermediate-term memory phase (B) of the Gibbs and Ng model of memory formation. The study also investigated the pyrogenic actions of polyinosinic:polycytidylic acid, and examined the effect of pretreatment with ketoprofen, a cyclooxygenase inhibitor. Significant rises in body temperature were observed 30 min after injection of polyinosinic:polycytidylic acid. Inhibition of cyclooxygenase by ketoprofen ameliorated the polyinosinic:polycytidylic acid-induced deficits in retention and attenuated the increase in body temperature. These results demonstrate that polyinosinic:polycytidylic acid induces memory processing deficits and is pyrogenic in the day-old chick and that these effects are cyclooxygenase-dependent.

Dorsal hippocampal dopamine receptors are involved in mediating ethanol state-dependent memory

In the present study, the effects of bilateral injections of dopaminergic agents into the hippocampal CA1 regions (intra-CA1) on ethanol (EtOH) state-dependent memory were examined in mice. A single-trial step-down passive avoidance task was used for the assessment of memory retention in adult male NMRI mice. Pre-training intra-peritoneal (i.p.) administration of EtOH (0.25, 0.5 and 1 g/kg) dose dependently induced impairment of memory retention. Pre-test administration of EtOH (0.5 g/kg)-induced state-dependent retrieval of the memory acquired under pre-training EtOH (0.5 g/kg) influence. Intra-CA1 administration of the dopamine D 1 receptor agonist, SKF 38393 (0.5, 1 and 2 g/mouse) or the dopamine D 2 receptor agonist, quinpirole (0.25, 0.5 and 1 μg/mouse) alone cannot affect memory retention. While, pre-test intra-CA1 injection of SKF 38393 (2 μg/mouse, intra-CA1) or quinpirole (0.25, 0.5 and 1 μg/mouse, intra-CA1) improved pre-training EtOH (0.5 g/kg)-induced retrieval impairment. Moreover, pre-test administration of SKF 38393 (0.5, 1 and 2 μg/mouse, intra-CA1) or quinpirole (0.5 and 1 μg/mouse, intra-CA1) with an ineffective dose of EtOH (0.25 g/kg) significantly restored the retrieval and induced EtOH state-dependent memory. Furthermore, pre-training injection of the dopamine D 1 receptor antagonist, SCH 23390 (4 μg/mouse), but not the dopamine D 2 receptor antagonist, sulpiride, into the CA1 regions suppressed the learning of a single-trial passive avoidance task. Pre-test intra-CA1 injection of SCH 23390 (2 and 4 μg/mouse, intra-CA1) or sulpiride (2.5 and 5 μg/mouse, intra-CA1) 5 min before the administration of EtOH (0.5 g/kg, i.p.) dose dependently inhibited EtOH state-dependent memory. These findings implicate the involvement of a dorsal hippocampal dopaminergic mechanism in EtOH state-dependent memory and also it can be concluded that there may be a cross-state dependency between EtOH and dopamine.

HIV-1 protein gp120 rapidly impairs memory in chicks by interrupting the glutamate–glutamine cycle

Learning and memory impairments are frequently observed in patients suffering from AIDS Dementia Complex (ADC). These effects have been linked to the presence of gp120, an HIV viral coat glycoprotein. The present study investigated the possibility that gp120 prevents the uptake of extracellular glutamate by astrocytes, leading to an interruption of the glutamate–glutamine cycle and a subsequent impairment of memory. Ten microliters of 10 nM gp120 was bilaterally injected into the region of the intermediate medial mesopallium of day-old chicks at various times before, or after, training using a single-trial passive avoidance task. Gp120 was found to significantly impair memory retention when injected 10–40 min after training. Memory impairments were evident within 5 min of gp120 administration and remained evident 24 h later. Further, the amnestic effect of gp120 could be overcome with glutamine or with precursors of glutamate synthesis, but only weakly by glutamate. These results support the conclusion that the amnestic effect of gp120 is due to an impaired uptake of glutamate by astrocytes and a subsequent interruption of glutamine supply to neurones. The data indicate that the glutamate–glutamine cycle may be a useful therapeutic target in the treatment of ADC.

Pharmaco-behavioural evidence indicating a complex role for ryanodine receptor calcium release channels in memory processing for a passive avoidance task

Calcium signalling is an important process underlying neuronal function and consequently behaviour. The release of calcium from intracellular stores via the ryanodine receptor calcium release (RyR) channel has been implicated in both synaptic plasticity and to a limited extent in memory processing. While past investigations have suggested a role for RyR channels in long-term memory, the present study suggests their action is more complex. Using a single trial passive avoidance task developed for the day-old chick, it is proposed that RyR channels are necessary both prior to the expression of long-term memory and also in retrieval processes. Specifically, 5 mM dantrolene (a specific RyR channel blocker) resulted in a persistent retention loss from 40 min post-training while 10 nM dantrolene produced a transient retention loss centred at 40 min post-training. We speculate that in the context of memory formation, RyR channels may be activated by nitric oxide and in the context of memory retrieval may lead to the activation of large conductance calcium-activated potassium BK Ca channels which, when blocked by 50 nM iberiotoxin, also demonstrated a transient retention loss centred at 40 min post-training.

Zaprinast consolidates long-term memory when administered to neonate chicks trained using a weakly reinforced single trial passive avoidance task

A weakly reinforced variant of the single trial passive avoidance task developed for the day-old chick typically fails to consolidate long-term memory. However, administration of zaprinast, a phosphodiesterase (PDE) type 5 inhibitor, (ic; 10 μl/side) immediately post-training resulted in a dose-dependent increase in retention at test 180 min post-training. Further, 100 μM zaprinast resulted in high levels of retention at test 180 min post-training when administered from 10 min before training to 10 min after training. Finally, 100 μM zaprinast, when administered immediately post-training, resulted in the consolidation of long-term memory at a number of times of test extending as late as 24 h post-training. Inhibition of PDE type 5 is known to increase cellular cGMP levels. Previous investigations using a strongly reinforced variant of this task have suggested a role for cGMP in memory retrieval, we now postulate that cGMP is also necessary for memory formation in chicks trained using passive avoidance.

Inhibition of endogenous carbon monoxide production induces transient retention losses in the day-old chick when trained using a single trial passive avoidance learning task

Carbon monoxide (CO) is most often thought of as an exogenous toxin rather than as a possible endogenous nootrope. However, a limited number of studies have suggested that CO is necessary in memory processing for at least some tasks. While nitric oxide (NO) and CO are known activators of guanylyl cyclase (GC), only the effect of NO on GC has been extensively investigated as a mechanism underlying memory processing. The aim of the present study was to determine if inhibition of CO production would have an effect on memory processing. Using chicks trained on a single trial passive avoidance task, inhibition of CO production using zinc (II) deuteroporphyrin IX 2,4-bis ethylene glycol (ZnBG; 5 μM) resulted in two transient retention losses occurring at around 40 and 130 min post-training. The timing of these transient retention losses was similar to those observed following inhibition of GC, using the same species and task in a previous study. This supports the notion that CO is necessary in memory processing for this task and may act through a GC-dependent mechanism. As ZnBG also directly inhibits GC or nitric oxide synthase (NOS) at high concentrations, a second experiment was carried-out to confirm the specificity of ZnBG for heme oxygenase (HO) at the concentration used. The action of ZnBG was challenged with the HO agonist hemin (100 μM) and the transient deficits were abolished. This confirmed that the action of ZnBG on memory was through a CO-related mechanism rather than directly on GC or NOS. In this way the specificity of ZnBG (5 μM) for HO could be confirmed. The results support a role for endogenous CO in memory processing, possibly through activation of GC. In addition, the transient retention losses observed following administration of ZnBG suggest that CO may be necessary for memory retrieval and not formation as previously thought.

The effects of the dopamine D1 receptor antagonist SCH23390 on memory reconsolidation following reminder-activated retrieval in day-old chicks

This series of experiments examined the involvement of the dopamine D1 receptor antagonist, SCH23390, on memory reconsolidation following reminder-activated retrieval. Day-old male New Hampshire × White Leghorn chicks were trained on a single trial passive avoidance task. A dose of 0.5 mg/kg of SCH23390 was administered subcutaneously 5 min before reminder trials, which were presented at 30, 60, and 90 min following training. Memory deficits were observed when reminder trials were presented at 30 and 60 min following training, but not when a reminder was presented at 90 min. No effect on memory retention was observed when reminder trials were not presented, suggesting that reconsolidation mechanisms were both contingent on the presentation of the reminder and independent of the consolidation process. Following a reminder presented at 60 min post-training, deficits in memory retention emerged between 45 and 60 min. The deficit was prolonged, lasting for up until 48 h after reminder presentation. The results indicate an important role for the D1 receptor in reconsolidation processes.

Noradrenaline involvement in the memory-enhancing effects of exposure to a complex rhythm stimulus following discriminated passive avoidance training in the young chick

Previous research in our laboratory has demonstrated a significant memory-enhancing effect of exposure to a complex rhythm stimulus following weakly-reinforced passive avoidance learning in chicks. The aim of this study was to explore whether noradrenaline mediates this process. Chicks were trained on a strongly-reinforced single-trial passive avoidance task involving discrimination between two coloured beads. Intracerebral administration of the protein synthesis blocker, anisomycin, revealed that a phase of memory formation sensitive to arousal levels was extended by approximately 35 min following exposure to the complex rhythm stimulus. Administration of 2,4-dinitrophenol showed that this extension occurred during phase B of intermediate-term memory. Finally, a higher dose of the β-adrenergic receptor antagonist, propranolol, was required to inhibit long-term memory in the presence of the auditory stimulus than in its absence. These findings suggest that the memory-enhancing effects of the complex rhythm stimulus may be mediated by noradrenaline, possibly via an increase in physiological arousal.

A scavenger of peroxynitrite prevents long-term memory formation using a single trial passive avoidance task for the day-old chick

The important role of nitric oxide (NO) in memory processing has been recognised for some time. However, the mechanisms through which NO may act are only partially understood. One highly reactive radical brought about by the reaction of NO and superoxide ions is peroxynitrite. The current study investigated the effect of peroxynitrite scavenging on retention for a single trial passive avoidance task developed for the day-old chick. Administration of a range of concentrations of the peroxynitrite scavenger Trolox (0.1 μM–1.2 mM) yielded a bimodal retention curve. This dose–response curve had nadirs at 300 and 800 μM. A time of administration study was conducted for each optimal concentration of Trolox and in both studies, the effective range of administration times extended from at least 10 min before training to 20 min post-training. Finally, a retention function was conducted for each optimum concentration of Trolox and in both studies a persistent retention loss was observed from 40 min post-training until the conclusion of the experiment 24 h post-training. The findings suggest that physiological levels of peroxynitrite may be required for the consolidation of long-term memory in this model of memory formation. Interestingly, the effective times of administration and time of retention loss onset are consistent with previous studies which blocked NO synthesis. Therefore it may be suggested that NO acts to facilitate long-term memory formation through the production of peroxynitrite.

Carryover Effects Associated with the Single-Trial Passive Avoidance Learning Task in the Young Chick

The single-trial passive avoidance task is a useful procedure for examining learning and memory in the young chick. However, it has recently been suggested that discrepant results reported by different laboratories are due to differences in training procedure. The present study investigated a number of parameters surrounding the passive avoidance task, using day-old White Leghorn, Black Australorp cockerels. The results suggested that presentation of a water-dipped bead immediately after the aversive bead significantly altered retention levels. In addition, when the water-dipped bead was presented after the aversive bead, chicks failed to discriminate between beads for a period of 10 min following exposure to the aversant experience. A novel variant of the passive avoidance procedure, involving pretraining with a water-dipped red bead, training with an aversant-coated red bead, and testing with a dry red bead, was evaluated. A measure of avoidance was calculated using all three trials. It is suggested that the use of a single bead, measured both before and after the training experience and using both aversant- and water-trained controls, results in the most concise characterization of memory-related phenomena in the chick which is not contaminated by a carryover effect from the aversive training experience to the nonaversive bead.

Inhibition of monoADP-Ribosylation Prevents Long-Term Memory Consolidation of a Single-Trial Passive Avoidance Task in the Day-Old Chick

The cytosolic posttranslational protein-modifying mechanism of monoADP-ribosylation has been implicated in long-term potentiation, a synaptic model of memory formation. The current study investigated the effect of inhibiting mono(ADP-ribosyl) transferase on memory for the passive avoidance task in day-old chicks (white Leghorn-black Australorp). Various doses of novobiocin or menadione sodium bisulfite were administered intracranially at different times before or after training. Control chicks were administered saline at matched times. Novobiocin (650 μM) or menadione sodium bisulfite (250 μM) administered between 5.0 min pretraining and 2.5 min posttraining was found to cause a persistent loss of retention from 120 min posttraining. These data provide the first demonstration that monoADP-ribosylation is required for the maintenance of long-term memory. Furthermore, the temporal characteristics of the memory loss caused by monoADP-ribosylation inhibition appears to exclude this mechanism as a downstream effect of the well-established nitric oxide activity previously shown to occur within 40 min of passive avoidance training.

Effects of adenosine receptor agonists and antagonists on pentylenetetrazole-induced amnesia

The effect of adenosine agents on amnesia induced by pentylenetetrazole was examined in mice. Post-training administration of pentylenetetrazole (50 and 60 mg/kg) disrupted 24-h retention of a single-trial passive avoidance task. The adenosine receptor antagonists, theophylline (2.5–25 mg/kg) and 8-phenyltheophylline (0.5–2 mg/kg), administered 30 min before and just after training at doses which did not affect retention, reduced the amnestic effect of pentylenetetrazole in a dose-dependent manner. Post-training administration of the adenosine A 1 receptor agonists, N 6-cyclohexyladenosine (CHA, 0.1 and 0.5 mg/kg) and N 6-phenylisopropyladenosine (R-PIA, 0.03 and 0.1 mg/kg), but not the adenosine A 2 receptor agonist, 5′- N-ethylcarboxamidoadenosine (NECA, 0.01 and 0.001 mg/kg), impaired retention. Nonamnestic doses of CHA and R-PIA potentiated the disruption induced by a lower dose of pentylenetetrazole (40 mg/kg). NECA did not induce any response in this respect. It is suggested that an adenosine A 1 receptor mechanism is involved in amnesia induced by pentylenetetrazole.

Lipopolysaccharide induces memory-processing deficits in day-old chicks

Recent evidence has demonstrated that immune activation can result in cognitive deficits due to the actions of the proinflammatory cytokines. These series of studies examined the effects of peripheral administration of lipopolysaccharide (LPS) on the memory processes of day-old chicks trained on a single-trial passive-avoidance task. LPS impaired performance in a dose- and time-dependent manner. Maximal impairment was produced by a dose of 2.5-mg/kg LPS administered 60 min prior to training. Retention tests revealed that deficits in memory processing appeared between 10 and 20 min posttraining. These results demonstrate an inhibitory effect of LPS on memory processing at the transition point from short-term memory to intermediate-term memory.

Changes in phosphorylation of Ca2+/calmodulin-dependent protein kinase II (CaMKII) in processing of short-term and long-term memories after passive avoidance learning.

Characteristic autophosphorylation of calcium/ calmodulin-dependent protein kinase II (CaMKII) and its consequences have made this kinase an interesting target in studying the molecular pathway for important neuronal functions including learning and memory formation. In this article, we use immunoprecipitation and immunoblotting methods to detect changes in phosphorylation of CaMKII during memory formation in 1-day-old chicks trained in a single trial passive avoidance task. A 60-kDa protein has been immunoprecipitated from the chick brain with an anti-rabbit CaMKII antibody. This protein shows strong and specific immunoactivities with antibodies against the calmodulin binding site of CaMKII, and the N and C terminals of beta-CaMKII. Commercially available anti-phosphoserine and anti-phosphothreonine antibodies are shown to sensitively detect phosphorylation of purified CaMKII. The basal phosphorylation of CaMKII from the intermediate medial hyperstriatum ventrale (IMHV) and lobus parolfactorius (LPO) regions of the chick brain is shown to be largely right hemisphere-lateralized. When chicks are subjected to a passive avoidance training experience, a specific increase in CaMKII phosphorylation is induced in the IMHV and LPO of the left hemisphere from those chicks whose memory for the training experience is successfully retrieved. While this specific increase in CaMKII phosphorylation is seen in both the left IMHV and left LPO in short-term memory, it is detectable only in the left LPO associated with long-term memory retrieval. The present results provide evidence that in vivo changes in phosphorylation of CaMKII are associated specifically with processing of distinct memory stages, which take place in specific brain regions.

Tyrosine kinase inhibitors impair long-term memory formation in day-old chicks

The involvement of protein kinases in numerous neuronal cellular processes, including learning and memory, has been well established, particularly regarding serine/threonine kinases. In the present study, the role of protein kinases in learning was further examined through an investigation of the effects of inhibitors of tyrosine kinase activity on memory formation. The present findings reveal that the intracranial administration of the tyrosine kinase inhibitors genistein and lavendustin A produced retention deficits in day-old chicks trained on a single-trial passive avoidance task. These deficits were not apparent until 90 min after the training episode and were not observed at all in chicks administered control substances. The possibility that the tyrosine phosphorylation disrupted by the presence of the inhibitors is related to NMDA glutamate receptor activation is considered.

Brief Retention Deficits Associated with Cyclically Recurring Left Hemisphere Events

In the chick, brief episodes of enhanced recall (“retrieval events”) recur approximately every 25 min in recall via the right hemisphere, and every 16 min in recall via the left. These events coincide with, and probably cause, the numerous transitions between memory phases described in the chick.; The most important of these is the transition to long-term memory, which is sometimes held to occur in chicks at about 50 min after learning, a transition picked out as unique by a variety of effects of amnesia-inducing agents, and by a brief impairment (“dip”) in recall at 55 min. We used a single trial passive avoidance task, involving bead pecking, to show that in chicks using only one eye, such dips occur not only at 55 min (in right-eyed chicks only) but also after each of the subsequent series of left hemisphere events (in left-eyed chicks only). Dips in recall appear to result when processes that are initiated by left hemisphere retrieval events result in hemispheric interaction, with one hemisphere (which can be either left or right) holding an inadequate trace (e.g., as a result of monocular training). Recall tests under such conditions may involve both the adequate and the inadequate trace, so that performance is impaired.

Inhibitors of cAMP-Dependent Protein Kinase Impair Long-Term Memory Formation in Day-Old Chicks

There is substantial evidence that protein kinases, through the phosphorylation of substrate proteins, play a significant role in information processing in the brain, including processes underlying memory formation. Inhibition of the activity of the cyclic-adenosine monophosphate-dependent protein kinase A by the highly specific inhibitor, halofantrine, resulted in impairment of memory formation in day-old chicks trained on a single-trial passive avoidance task. A dose of 9.6 ng/chick halofantrine induced amnesia at the beginning of a protein synthesis-dependent long-term memory stage, the last of three stages of memory postulated to underly memory formation in the chick following passive avoidance learning. The concentration of halofantrine required for 50% inhibition of chick brain protein kinase A was found to be similar to that observed for bovine heart and rat liver. The amnestic effect of halofantrine is tentatively attributed to interference with de novo protein synthesis necessary for long-term memory consolidation. Neither anthraquinone nor the anthraquinone derivative anthraflavic acid, which have little effect on protein kinase A activity, affected memory retention. On the other hand, two other anthraquinone derivatives, chrysophanic acid and purpurin, which inhibit PKA activity, at doses of 0.25 and 0.5 ng/chick also yielded retention deficits. In these cases, however, retention losses occurred earlier than observed with halofantrine, at about 30 min post-training. The earlier effects of these inhibitors may be due to the additional inhibitory action of these compounds on protein kinase C activity, which has been demonstrated in previous studies to be implicated, possibly through phosphorylation of the GAP43 phosphoprotein, in memory processing in the stage of memory immediately preceding the protein synthesis-dependent long-term stage.