Inhibitory Avoidance In Rats Research Articles

Autophagy coupled to translation is required for long-term memory

ABSTRACT An increase in protein synthesis following learning is a fundamental and evolutionarily conserved mechanism of long-term memory. To maintain homeostasis, this protein synthesis must be counterbalanced by mechanisms such as protein degradation. Recent studies reported that macroautophagy/autophagy, a major protein degradation mechanism, is required for long-term memory formation. However, how learning regulates autophagy and recruits it into long-term memory formation remains to be established. Here, we show that inhibitory avoidance in rats significantly increases the levels of autophagy and lysosomal degradation proteins, including BECN1/beclin 1, LC3-II, SQSTM1/p62 and LAMP1, as well as autophagic flux in the hippocampus. Moreover, pharmacological inhibition or targeted molecular disruption of the learning-induced autophagy impairs long-term memory, leaving short-term memory intact. The increase in autophagy proteins results from active translation of their mRNA and not from changes in their total mRNA levels. Additionally, the induction of autophagy requires the immediate early gene Arc/Arg3.1. Finally, in contrast to classical regulation of autophagy in other systems, we found that the increase in autophagy upon learning is dispensable for the increase in protein synthesis. We conclude that coupling between learning-induced translation and autophagy, rather than translation per se, is an essential mechanism of long-term memory. Abbreviations: AAV: adeno-associated virus; ARC/ARG3.1: activity regulated cytoskeletal-associated protein; ATG: autophagy related; DG: dentate gyrus; GFP: green fluorescent protein; IA: inhibitory avoidance; LAMP1: lysosomal-associated membrane protein 1; MAP1LC3B/LC3B: microtubule-associated protein 1 light chain 3 beta; ODN: oligodeoxynucleotide; qPCR: quantitative polymerase chain reaction; SBI: SBI0206965; SQSTM1/p62: sequestosome 1; SUnSET: surface sensing of translation; TRAP: translating ribosome affinity purification; ULK1: unc-51 like kinase 1

On the boundary conditions of avoidance memory reconsolidation: An attractor network perspective

The reconsolidation and extinction of aversive memories and their boundary conditions have been extensively studied. Knowing their network mechanisms may lead to the development of better strategies for the treatment of fear and anxiety-related disorders. In 2011, Osan et al. developed a computational model for exploring such phenomena based on attractor dynamics, Hebbian plasticity and synaptic degradation induced by prediction error. This model was able to explain, in a single formalism, experimental findings regarding the freezing behavior of rodents submitted to contextual fear conditioning. In 2017, through the study of inhibitory avoidance in rats, Radiske et al. showed that the previous knowledge of a context as non-aversive is a boundary condition for the reconsolidation of the shock memory subsequently experienced in that context. In the present work, by adapting the model of Osan et al. (2011) to simulate the experimental protocols of Radiske et al. (2017), we show that such boundary condition is compatible with the dynamics of an attractor network that supports synaptic labilization common to reconsolidation and extinction. Additionally, by varying parameters such as the levels of protein synthesis and degradation, we predict behavioral outcomes, and thus boundary conditions that can be tested experimentally.

Inhibition of acetylcholinesterase activity in brain and behavioral analysis in adult rats after chronic administration of fenproporex

Fenproporex is an amphetamine-based anorectic and it is rapidly converted in vivo into amphetamine. It elevates the levels of extracellular dopamine in the brain. Acetylcholinesterase is a regulatory enzyme which is involved in cholinergic synapses and may indirectly modulate the release of dopamine. Thus, we investigated whether the effects of chronic administration of fenproporex in adult rats alters acquisition and retention of avoidance memory and acetylcholinesterase activity. Adult male Wistar rats received repeated (14days) intraperitoneal injection of vehicle or fenproporex (6.25, 12.5 or 25mg/kgi.p.). For behavioral assessment, animals were submitted to inhibitory avoidance (IA) tasks and continuous multiple trials step-down inhibitory avoidance (CMIA). Acetylcholinesterase activity was measured in the prefrontal cortex, hippocampus, hypothalamus and striatum. The administration of fenproporex (6.25, 12.5 and 25mg/kg) did not induce impairment in short and long-term IA or CMIA retention memory in rats. In addition, longer periods of exposure to fenproporex administration decreased acetylcholinesterase activity in prefrontal cortex and striatum of rats, but no alteration was verified in the hippocampus and hypothalamus. In conclusion, the present study showed that chronic fenproporex administration decreased acetylcholinesterase activity in the rat brain. However, longer periods of exposure to fenproporex did not produce impairment in short and long-term IA or CMIA retention memory in rats.

Regulation of Fear Memory by Glucocorticoid and Cholinergic Receptors within the Dorsal Striatum

GENERAL COMMENTARY article Front. Behav. Neurosci., 19 July 2012Sec. Learning and Memory Volume 6 - 2012 | https://doi.org/10.3389/fnbeh.2012.00042

Participation of hippocampal cholinergic system in memory persistence for inhibitory avoidance in rats

Memory persistence needs a new event of consolidation 12h after the acquisition. We investigated the role of the cholinergic activity on the persistence of memory. For this purpose, we performed the treatments 9 or 12h after acquisition and the memory tested 2 or 7days after inhibitory avoidance (IA) training. Here we report that activity of medial septum, by transitorily inactivating this structure with lidocaine 12h after IA training, is essential for memory persistence at the 7th day, but not for the formation at the 2nd day. We also report that muscarinic and nicotinic cholinergic receptors of CA1 area are engaged on memory persistence. Since scopolamine (mAChRs antagonist) and mecamylamine (nAChRs blocker) infusions, 12h post-training, demonstrated impairment on long term memory (LTM), persistence on the 7th day but no effect on LTM formation was found on the 2nd day in the IA test. The same effects were found with pirenzepine, an M1 antagonist. No effects on the formation and persistence of memory on the 2nd and 7th days were demonstrated after DHβE infusions (nAChRs subtype antagonist α4β2, α3β2). These findings suggest that mAChR and nAChR at the CA1 area, and also MS activation, are required for the persistence of memory.

Histamine reverses a memory deficit induced in rats by early postnatal maternal deprivation

Early partial maternal deprivation causes long-lasting neurochemical, behavioral and brain structural effects. In rats, it causes a deficit in memory consolidation visible in adult life. Some of these deficits can be reversed by donepezil and galantamine, which suggests that they may result from an impairment of brain cholinergic transmission. One such deficit, representative of all others, is an impairment of memory consolidation, clearly observable in a one-trial inhibitory avoidance task. Recent data suggest a role of brain histaminergic systems in the regulation of behavior, particularly inhibitory avoidance learning. Here we investigate whether histamine itself, its analog SKF-91844, or various receptor-selective histamine agonists and antagonists given into the CA1 region of the hippocampus immediately post-training can affect retention of one-trial inhibitory avoidance in rats submitted to early postnatal maternal deprivation. We found that histamine, SKF-91844 and the H2 receptor agonist, dimaprit enhance consolidation on their own and reverse the consolidation deficit induced by maternal deprivation. The enhancing effect of histamine was blocked by the H2 receptor antagonist, ranitidine, but not by the H1 receptor antagonist pyrilamine or by the H3 antagonist thioperamide given into CA1 at doses known to have other behavioral actions, without altering locomotor and exploratory activity or the anxiety state of the animals. The present results suggest that the memory deficit induced by early postnatal maternal deprivation in rats may in part be due to an impairment of histamine mediated mechanisms in the CA1 region of the rat hippocampus.

The anterior cingulate cortex is involved in retrieval of long-term/long-lasting but not short-term memory for step-through inhibitory avoidance in rats

It is known that the anterior cingulate cortex (ACC) is involved in the formation of contextual fear memory. It has been shown that the ACC is important for the retrieval of long-term contextual fear memory. In order to further examine the role of the ACC in fear memory, we investigated the effects of chemical lesion to or reversible inactivation of the ACC on the retrieval of long-term and short-term step-through inhibitory avoidance (IA) memory. Chemical lesion to the ACC by quinolinic acid severely impaired the retrieval of 15-day and 29-day memories for one-trial step-through IA. Pre-retrieval inactivation of the ACC by locally infusing muscimol, a selective GABA A receptor agonist, produced a severe deficit in 7-day, 4-day and 1-day IA memories, with no effect on 2-h and 6-h memories. Thus, the ACC is required for the retrieval of long-term/long-lasting IA memory, but is dispensable for short-term one.

P.8.071 Effects of the metabotropic glutamate receptor subtype5 blockade on inhibitory avoidance in rats

P.8.071 Effects of the metabotropic glutamate receptor subtype5 blockade on inhibitory avoidance in rats

Inhibition of PKC in basolateral amygdala and posterior parietal cortex impairs consolidation of inhibitory avoidance memory

Hippocampal α- and βI/βII protein kinase C (PKC) are crucial for the formation of different types of memory in several species, including that for a one trial inhibitory avoidance (IA) task in rats. Many studies, however, have shown that other brain structures besides the hippocampus, notably the basolateral amygdala (BLA) and posterior parietal cortex (PC) are also necessary for memory consolidation. Here, we examine the role of α- and βI/βII PKC in the BLA and PC on the consolidation of the memory for IA in rats. The selective inhibitor of α- and βI/βII-PKC Gö 6976 and the nonselective PKC inhibitor Gö 7874 were administered into these structures at different times after training at concentrations known to inhibit PKC and to produce retrograde amnesia when given into the hippocampus. Gö 7874 blocked consolidation of IA memory when infused into BLA immediately and 30 min or into PC 180 to 360 min posttraining. Gö 6976 caused amnesia when given into the BLA also immediately or 30 min posttraining but in the PC hindered memory retention only when infused 270 and 360 min after the training session. Our data indicate that α- and βI/βII-PKC are critical for consolidation of IA memory shortly after training in BLA and that, first other isoforms and subsequently the α- and βI/βII PKC are required 3 or more hours after training in the PC. The findings on BLA are similar to those previously reported in the hippocampus, but those on PC suggest an entirely different molecular dynamics for memory formation in that area.

Participation of hippocampal nicotinic receptors in acquisition, consolidation and retrieval of memory for one trial inhibitory avoidance in rats

Participation of hippocampal nicotinic receptors in acquisition, consolidation and retrieval of memory for one trial inhibitory avoidance in rats

Participation of hippocampal nicotinic receptors in acquisition, consolidation and retrieval of memory for one trial inhibitory avoidance in rats

One-trial step-down inhibitory avoidance in rats involves the activation of two separate memory types, a short-term system (STM) that lasts 3–6 h, and a long-term system (LTM) that takes 3–6 h to be formed and lasts for many days or even months. Here we investigate the effect of nicotinic receptor (nAChR) ligands infused bilaterally in the hippocampus on STM and LTM formation and on LTM retrieval of this task. Rats were implanted with chronic cannulae in the CA1 region of the dorsal hippocampus, trained using a 0.5 mA foot shock, and tested twice, first 1.5 h after training to measure STM, and again at 24 h to measure LTM. The drugs used were the nAChR antagonists, mecamylamine (1, 3 and 10 μg/side) and dihydro-β-erythroidine (DHβE; 2, 6 and 18 μg/side) and the agonist, nicotine (0.6, 1 and 3 μg/side). They were given either 15 min before training, immediately after training or 15 min prior to LTM retrieval. Mecamylamine and DHβE impaired and nicotine enhanced STM, LTM and retrieval similarly. The results indicate that nAChRs in CA1 participate in the regulation of both STM and LTM formation, and on the retrieval of LTM.

AMPA/kainate and group-I metabotropic receptor antagonists infused into different brain areas impair memory formation of inhibitory avoidance in rats.

Several lines of evidence suggest that glutamate receptors are involved in memory processing. To examine the role of non-N-methyl-D-aspartate (non-NMDA) glutamate receptors on memory consolidation, rats were bilaterally implanted with cannulae aimed at the CA1 region of the dorsal hippocampus (CA1), entorhinal cortex (ENTO), posterior parietal cortex (PPC) or the basolateral nucleus of the amygdala (BLA), and trained in a one-trial step-down inhibitory avoidance task. At different times after training, the alpha-amino 3-hydroxy-5 methyl 4-isoxazole propionate (AMPA) receptor blocker, 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX) (1.0 microg/side), or the metabotropic type-I receptor antagonist, 2-amino-3-phosphonopropionic acid (AP3) (1.0 microg/side), were infused into the above-mentioned structures. CNQX produced retrograde amnesia when infused into BLA or CA1 0, 30, 90 or 180 min post-training but not at later times. AP3 blocked memory consolidation when administered into CA1 0, 30 or 180 min post-training, while in BLA, it was amnestic only when given 0 or 30 min after the training session. CNQX and AP3 had no effect on memory when administered into ENTO or PPC at any time. Our data suggest that the consolidation of the avoidance memory requires intact non-NMDA receptor function in the hippocampus and the basolateral nucleus of the amygdala, but not necessarily in the entorhinal and parietal cortex, for long periods after training.

Effects of excitotoxic median raphe lesion on working memory deficits produced by the dorsal hippocampal muscarinic receptor blockade in the inhibitory avoidance in rats

The experiments investigated the interactions between median raphe nucleus (MRN) serotonergic and septo-hippocampal muscarinic cholinergic systems in the modulation of forming and storing performances of working memory. Rats with ibotenic acid-induced MRN-lesion bilaterally received scopolamine (2–4 μg/each side) infusion into the dentate gyrus of the dorsal hippocampus and were tested in a single trial step-through inhibitory avoidance. Initial preference to the dark compartment (escape latency) was taken as the measure of non-mnemonic behaviours and response latency to enter the dark compartment immediately after the foot-shock was used to measure working memory. The high-dose scopolamine infusion 10 min before the training decreased escape latencies in the sham-lesioned rats, whereas had no effect in the MRN-lesioned rats. Although MRN lesion per se did not alter response latency, it alleviated pre-training scopolamine-induced decrease, but aggravated post-training scopolamine-induced reduction in this parameter. These results suggest that the antagonistic interactive processes between MRN-serotonergic and hippocampal cholinergic systems modulate non-mnemonic component of working memory formation, whereas the storing performance of working memory is modulated by the synergistic interactions between these systems in the hippocampus, mainly in the dentate gyrus.

Effects of Posttraining Treatments in the Posterior Cingulate Cortex on Short- and Long-Term Memory for Inhibitory Avoidance in Rats

Adult male Wistar rats were bilaterally implanted with indwelling cannulae in the caudal region of the posterior cingulate cortex. After recovery, animals were trained in a step-down inhibitory avoidance task (3.0-s, 0.4-mA foot shock) and received, right after training, a 0.5-μl infusion of vehicle (phosphate-buffered saline, pH 7.4), of the GABAA receptor agonist muscimol (0.1 or 0.5 μg), of the cAMP-dependent protein kinase (PKA) stimulant Sp-cAMPS (0.1 or 0.5 μg), or of the PKA inhibitor Rp-cAMPS (0.1 or 0.5 μg). Animals were tested twice, 1.5 h and, again, 24 h after training, in order to examine the effects of these agents on short- and long-term memory, respectively. Muscimol (0.5 but not 0.1 μg) hindered retention for both short- and long-term memory (p < .05). Rp-cAMPS (0.1 or 0.5 μg) hindered retention for short-term memory (p <.05). In addition, these animals showed lower, but not significantly lower, latencies than controls in the test session for long-term memory (p > .10). A trend toward an amnesic effect on long-term memory was also observed after Sp-cAMPS infusion at 0.1 μg (p < .10). These results show that strong stimulation of GABAergic synapses in the caudal region of the rat posterior cingulate cortex right after training impairs short- and long-term memory (the latter less dramatically). The same occurs by inhibiting PKA activity with regard to STM and possibly to LTM.

Blockade of adenosine A 1 receptors in the posterior cingulate cortex facilitates memory in rats

Male Wistar rats were bilaterally implanted with indwelling cannulae in the caudal region of the posterior cingulate cortex. After recovery, animals were trained in a step-down inhibitory avoidance task (3.0-s, 0.4-mA foot shock) and received, immediately after training, a 0.5-μl infusion of the adenosine A 1 receptor agonist N6-cyclopentyladenosine (CPA; 1, 50 or 100 nM) or of the adenosine A 1 receptor antagonist 8-cyclopentyl-1,3-dipropylxanthine (DPCPX; 1, 25 or 50 nM). Animals were tested twice, 1.5 h and, again, 24 h after training, in order to examine the effects of these agents on short- and long-term memory, respectively. Only 50-nM DPCPX was effective in altering memory, promoting a facilitation. These results suggest that adenosine A 1 receptors in the posterior cingulate cortex inhibit memory consolidation in a way that their blockade facilitates memory for inhibitory avoidance in rats.

LY294002, an inhibitor of phosphoinositide 3-kinase given into rat hippocampus impairs acquisition, consolidation and retrieval of memory for one-trial step-down inhibitory avoidance.

Adult male Wistar rats were bilaterally implanted with indwelling cannulae in the CA1 region of the dorsal hippocampus. Once recovered from surgery, animals were submitted to one session of step-down inhibitory avoidance training (3.0 s, 0.4 mA footshock). Animals received a 0.5-microl infusion of saline, or of LY294002 (5, 50 or 500 microM), an inhibitor of the phosphoinositide 3-kinase (PI 3-K) family. Infusions were given 10 min before training, immediately post-training or 10 min prior to a 24-h retention test. In the pre- and post-training groups, the animals were tested twice: at 1.5 and 24 h after training, for short- (STM) and long-term memory (LTM), respectively. Pre- and post-training infusion of the drug inhibited both STM and LTM. Pre-test infusions impaired LTM retrieval. The effects can not be attributed to influences on locomotor, exploratory, pro- or anti-conflict behaviour, since LY294002 had no influence on elevated plus-maze behaviour. The results suggest that hippocampal PI 3-K is necessary for memory acquisition, consolidation and retrieval of the consolidation of step-down inhibitory avoidance in rats. This could be due to an interaction with the N-methyl-d-aspartate (NMDA) receptor complex or with activity of the extracellularly regulated protein kinase (ERK)-Ras signalling pathway.

Involvement of the serotonergic type 1A (5-HT1A) receptor in the agranular insular cortex in the consolidation of memory for inhibitory avoidance in rats.

Adult male Wistar rats were bilaterally implanted with indwelling cannulae in the agranular insular cortex of the prefrontal cortex. After recovery, animals were trained in a step-down inhibitory avoidance task (3.0-s, 0.4-mA footshock) and received, immediately after training, a 0.5-microl infusion of the serotonergic type 1A (5-HT1A) receptor agonist dipropylamino-8-hydroxy-1,2,3,4-tetrahydronaphthalene hydrobromide (8-OH-DPAT) or of the 5- HT1A receptor antagonist 1-(2-methoxyphenyl)-4-[4-(2-phthalimido)butyl] piperazine hydrobromide (NAN-190), or of vehicle alone (20% DMSO). Retention testing was carried out 24 h after training. 8-OH-DPAT (1.25 and 6.25 microg but not 0.0125 or 0.125 microg) was amnesic. NAN-190 was not effective at 0.125 or 1.25 microg any dose but reversed amnesia when given at 1.250 microg simultaneously with both effective doses of 8-OH-DPAT. These results show that an overactivation of 5-HT1A receptors in the agranular insular cortex impairs memory consolidation of inhibitory avoidance, in rats, immediately after training. This suggests that these receptors of the insular cortex may modulate memory consolidation.

Guanosine impairs inhibitory avoidance performance in rats.

The nucleoside guanosine, previously found to exert trophic and neuroprotective effects, was found to impair retention of inhibitory avoidance responses, with a complete effect at 7.5 mg/kg i.p. pretraining. Treated animals, when retrained 1 week later, showed normal learning ability. Guanosine injected immediately after training or pretest did not alter retention latency. Combined pretraining and pretest treatments with guanosine failed to reverse its amnestic effect, excluding the contribution of state dependency. Open field parameters and shock sensitivity were mostly unaltered by guanosine. These results suggest an amnestic effect of guanosine on inhibitory avoidance in rats, in a pattern compatible with inhibition of glutamatergic activity. However, the mechanism for the amnestic effect of guanosine is yet to be elucidated.

Infusions of AP5 into the basolateral amygdala impair the formation, but not the expression, of step-down inhibitory avoidance.

We evaluated the effects of infusions of the NMDA receptor antagonist D,L-2-amino-5-phosphonopentanoic acid (AP5) into the basolateral nucleus of the amygdala (BLA) on the formation and expression of memory for inhibitory avoidance. Adult male Wistar rats (215-300 g) were implanted under thionembutal anesthesia (30 mg/kg, ip) with 9.0-mm guide cannulae aimed 1.0 mm above the BLA. Bilateral infusions of AP5 (5.0 microg) were given 10 min prior to training, immediately after training, or 10 min prior to testing in a step-down inhibitory avoidance task (0.3 mA footshock, 24-h interval between training and the retention test session). Both pre- and post-training infusions of AP5 blocked retention test performance. When given prior to the test, AP5 did not affect retention. AP5 did not affect training performance, and a control experiment showed that the impairing effects were not due to alterations in footshock sensitivity. The results suggest that NMDA receptor activation in the BLA is involved in the formation, but not the expression, of memory for inhibitory avoidance in rats. However, the results do not necessarily imply that the role of NMDA receptors in the BLA is to mediate long-term storage of fear-motivated memory within the amygdala.

Chronic Corticosterone Impairs Inhibitory Avoidance in Rats: Possible Link With Atrophy of Hippocampal CA3 Neurons

V. BISAGNO, M. FERRINI, H. RIOS, L. M. ZIEHER AND S. I. WIKINSKI. Chronic corticosterone impairs inhibitory avoidance in rats: Possible link with atrophy of hippocampal CA3 neurons. PHARMACOL BIOCHEM BEHAV 66(2) 235–240, 2000.—The aim of our work was to evaluate the effect of a chronic (22 days) administration of corticosterone, which induces supraphysiological serum levels of the hormone, on an inhibitory avoidance learning in rats (one-trial step-through learning task, footshock: 0.5 mA, 2 s). We also studied hippocampal markers of neuroanatomical CA3 pyramidal neuron atrophy by using the Golgi staining method. Chronic exposure to high CORT serum levels induced a significant impairment of inhibitory avoidance learning. The CORT group also showed hippocampal glucocorticoid receptor (GR) downregulation and the decrease of hippocampal CA3 branch points and total dendritic length in the apical tree that would be causally related with the learning impairment.