Active Avoidance Retention Research Articles

Associative learning deficit in two experimental models of hepatic encephalopathy

People with hepatic insufficiency can develop hepatic encephalopathy (HE), a complex neuropsychological syndrome covering a wide range of neurological and cognitive and motor alterations. The cognitive deficits include disturbances in intellectual functions such as memory and learning. In spite of its high prevalence in western societies, the causes of HE have not yet been clearly established. For this reason, experimental models of HE are used to study this condition. In this work, two experimental models were used, one Type B HE (portacaval shunt) and the other Type C HE (cirrhosis by intoxication with thioacetamide), to evaluate its effect on two tasks of associative learning: two-way active avoidance and step-through passive avoidance. The results show an impediment both in acquisition and retention of active avoidance in both models of HE. However, in passive avoidance, only the rats with portacaval shunt presented a memory deficit for the aversive event. In our opinion, these results can be explained by alterations in the neurotransmission system presented by animals with hepatic insufficiency, which are mainly caused by a rise in cerebral histamine and a dysfunction of the glutamatergic system.

Parafascicular electrical stimulation attenuates nucleus basalis magnocellularis lesion-induced active avoidance retention deficit

Previous experiments from our laboratory showed that retention of two-way active avoidance learning is improved by post-training intracranial electrical stimulation (ICS) of the parafascicular nucleus (PF) and impaired by pre-training electrolytic lesions of the nucleus basalis magnocellularis (NBM). The question investigated here was whether post-training PF ICS is able to attenuate the active avoidance retention deficit observed in rats lesioned pre-training in the NBM. To this goal, the following experimental design was used: rats bilaterally lesioned in the NBM and stimulated in the PF, rats lesioned in the NBM, rats stimulated in the PF, control rats implanted in the PF, and sham-operated rats were first trained in a shuttle-box for a single 30-trial session and tested again following two successive retention intervals (24 h and 11 days). The results showed that: (1) NBM lesions impaired the 11-day performance without affecting either the acquisition or the 24-h retention of the avoidance learning; (2) PF ICS treatment in unlesioned rats improved performance in both retention sessions only when the stimulation was applied in the posterior region of the nucleus; and (3) stimulation of the posterior PF compensated the 11-day retention impairment induced by NBM lesions. These results are discussed in relation to the interaction of arousal systems in the modulation of cognitive processes.

Nucleus basalis magnocellularis electrical stimulation facilitates two-way active avoidance retention, in rats

We studied the effects of post-training intracranial electrical stimulation of the nucleus basalis magnocellularis on two-way active avoidance retention. After the acquisition, rats were stimulated for 20 min, and they were tested again after 24 h or 11 days. The treatment improved memory consolidation, especially in animals with a low initial learning ability. These facilitative effects could be attributed to an enhancement of cortical and/or amygdala activation, leading to an improvement in associative processes and/or cortical plasticity.

Effect of Indian Hypericum perforatum Linn on animal models of cognitive dysfunction

The effect of a standardised 50% ethanolic extract of Indian Hypericum perforatum (IHp) was investigated for its putative nootropic activity on various experimental paradigms of learning and memory, viz. transfer latency (TL) on elevated plus-maze, passive avoidance (PA), active avoidance (AA), scopolamine and sodium nitrite induced amnesia (SIA & NIA) in albino rats. Pilot studies indicated that single dose administration of IHp had little or no acute behavioural effects, hence the extract of IHp was administered orally at two dose levels (100 and 200 mg/kg, p.o.), once in daily for three consecutive days, while piracetam (500/kg, i.p.), a clinically used nootropic agent, was administered acutely to rats as the standard drug. Control rats were treated with equal volume of vehicle (0.3% carboxymethyl cellulose (CMC)). IHp and piracetam when given alone shortened the TL on day 1, 2, 9 and also antagonised the amnesic effects of scopolamine and sodium nitrite on the TL significantly. IHp had no significant per se effect on the retention of the PA in rats. Only the higher dose (200 mg/kg, p.o.) produced a significant reversal of scopolamine induced PA retention deficit but no significant reversal was observed with sodium nitrite. Piracetam showed significant per se facilitatory effect on PA retention and also reversed the scopolamine and sodium nitrite induced impaired PA retention. In the AA test, IHp in both the doses, and piracetam, facilitated the acquisition and retention of AA in rats and the IHp effects were found to be dose dependent. Both the doses of IHp and piracetam significantly attenuated the scopolamine and sodium nitrite induced impaired retention of AA. These results indicate a possible nootropic action of IHp, which was qualitatively comparable with that induced by piracetam.

Tuberomammillary nucleus lesion facilitates two-way active avoidance retention in rats

To evaluate whether the tuberomammillary nucleus might be involved in the acquisition and/or retention of a two-way active avoidance conditioning, rats were given a unilateral lesion of the tuberomammillary nucleus (E2 region) 24 h prior to the first conditioning session. Four learning sessions were performed: one acquisition and 3 retention sessions (short-term, 24 h; and longterm, 8 and 18 days). Results showed that the lesion facilitated the long-term retention of conditioning, but no effects were observed on acquisition and short-term retention. Since rewarding intracranial electrical stimulation seems to be a consistent way to facilitate learning and memory processes, and tuberomammillary lesion has been shown to improve intracranial self-stimulation behavior (ICSS), we suggest that lesions in the present experiment could have facilitated two-way active avoidance retention by enhancing the function of brain reward mechanisms.

Leu]enkephalin and its metabolite, Tyr-Gly-Gly, impair active avoidance retention

The current study examined the effects of [leu]enkephalin and its metabolite, Tyr-Gly-Gly, given immediately posttraining on active avoidance performance measured 24 h later. Initial experiments revealed that, in comparison to zero or one training trials, providing mice with two training trials significantly increased active avoidance performance measured 24 h later; this enabled us to examine the effects on retention of peptides administered immediately after the two training trials. It was found that Tyr-Gly-Gly (16 and 53 μg/kg) and [leu]enkephalin (30 and 100 μg/kg) administered in this fashion both significantly impaired retention; the dose-response functions for both peptides were U-shaped. Since the effects of enkephalins are most likely mediated by opioid δ-receptors, and Tyr-Gly-Gly has little or no activity at opioid receptors, the effects of the parent peptide(s) and metabolite are presumably pharmacologically distinct.

Impairment of active avoidance by the noradrenergic neurotoxin, DSP4: attenuation by post-training epinephrine

Male Sprague-Dawley rats were treated with the selective noradrenergic neurotoxin, DSP4 prior to behavioral assessment. They were trained in an inhibitory avoidance and a one-way active avoidance task and given post-training treatment with epinephrine (EPI, 0.1 mg/kg, SC) or physiological saline. Performance on these tests was assessed at time points after treatment with DSP4 when (1) both central NE and sympathetic catecholamines were depleted and when (2) sympathetic catecholamines had returned to control levels and central NE remained depleted. Activity was also assessed at two time points after DSP4 treatment. DSP4 treatment had no effect upon inhibitory avoidance retention but impaired one-way active avoidance shuttle performance at both time points following DSP4 treatment. There was a transient depression of spontaneous activity which may indicate a deficit of behavioral initiation during the early phase after DSP4 treatment when the sympathetic catecholamine levels were depleted. This finding suggests that the peripheral sympathetic system may support some aspect of behavioral initiation. Epinephrine (0.1 mg/kg SC) administered after active avoidance training ameliorated the active avoidance retention performance deficit seen 4 days after DSP4 treatment. Post-training EPI did not significantly affect active avoidance retention performance when animals were trained and tested after peripheral sympathetic recovery (approximately 2 weeks after DSP4 treatment).(ABSTRACT TRUNCATED AT 250 WORDS)

Behavioral activity and active avoidance learning and retention in rats neonatally exposed to painful stimuli

Twice daily for the first 15 days after birth, rats from the same litters were either placed for 5 sec on a hot plate (55°C) (treated group), or on a plate maintained at body temperature (38°C) (manipulated group). Controls were left undisturbed. When 90 days old, they were studied for pain threshold, open-field behavior, and two-day active avoidance learning and retention. Weight gain, pain threshold, open-field behavior, and active avoidance retention were not significantly different in the three groups. On the other hand, the rate of two-way active avoidance learning was significantly greater in treated rats. These results suggest that repeated neonatal exposure to painful stimuli, in rats raised under otherwise normal conditions, improves later active avoidance performance. The most likely mechanisms are discussed.

Memory facilitation and impairment with supraseizure electrical brain stimulation: attenuation with pretrial propranolol injections

Post-training supraseizure stimulation of frontal cortex enhances retention of active avoidance in rats trained using a low footshock but impairs retention when high footshock is used in training. Pretreatment with the adrenergic antagonist propranolol results in attenuation of both memory facilitation and amnesia. These results are consistent with previous evidence indicating that adrenergic antagonists attenuate amnesia and facilitation produced by a variety of agents and suggest that memory modulatory treatments may enhance or impair memory by actions which include effects on adrenergic systems.

Serotonin neurons and aversive conditioning in the rat.

The acute and long‐term effects of p‐chloroamphetamine (PCA) on one‐way and two‐way active avoidance (AA), passive avoidance (PA) learning, fear retention (FR) and on central monoamine concentrations were examined in the male rat. Acute PCA administration (0.63–5 mg/kg i.p.), which releases presynaptic 5‐HT, produced a dose‐related impairment of both one‐and two‐way AA acquisition, AA retention, PA and fear retention. The selective serotonin (5‐HT) uptake inhibitor zimelidine, but not the noradrenaline (NA) uptake inhibitor desipramine, blocked the avoidance deficit induced by acute PCA. Degeneration of brain 5‐HT neurons by a high neurotoxic dose of PCA (2 × 10 mg/kg i.p.) failed to change AA and PA learning but blocked the avoidance deficit induced by acute PCA. Degeneration of locus coeruleus NA neurones with DSP4 (1 × 50 mg/kg), a selective NA neurotoxin, failed to block the acute PCA action. Thus, the acute avoidance learning impairment appears to be specifically related to the acute release of endogenous 5‐HT. Both acute and long‐term PCA treatment affected 5‐HT neurones preferentially in the forebrain while marginal effects were observed in the midbrain and spinal cord. A marked impairment in the retention and retrieval of fear conditioning in the rat was also observed following acute PCA administration. The serotoninergic mechanisms underlying the retrieval deficit were found to be similar but not identical to those involved in AA acquisition. These results suggest an important role for central 5‐HT neurones in aversive learning processes. The possible involvement of 5‐HT neurones in learning, memorial and/or retrieval processes is discussed.

Age-dependent contextual effects on short-term active avoidance retention in rats

Two experiments examined age-related differences in short-term retention of active avoidance in rats through manipulation of context. While adult and preweanling rats showed equally good immediate retention of the avoidance task when an odor contextual cue was held constant between training and testing, the performance of preweanlings was significantly disrupted compared to that of adults when the testing-context odor differed from that of training. The same results were obtained whether the animals had no prior experience with the odors (Experiment I) or had previously been exposed to the contextual cues (Experiment II). Results are considered in terms of their implications for the ontogeny of memory storage and retention.

Reactivation-Induced Proactive Interference in Rats

Reactivation of passive avoidance information just prior to active avoidance learning resulted in significant decrements in retention of active avoidance by rats. Furthermore, the amount of retention decrement increased as the retention interval following active avoidance training was lengthened. Contrary to previous findings, these data suggest that for proactive interference to occur, an animal need not acquire two, conflicting responses within a short temporal interval.

The effects of dorsal bundle injections of 6-hydroxydopamine on avoidance responding in rats.

1 The effect of injection of 6-hydroxydopamine (6-OHDA) into the fibres of the dorsal noradrenergic bundle on acquisition, retention and extinction of active avoidance in rats were examined. 2 6-OHDA injections severely depleted noradrenaline in all forebrain areas assayed, with the interesting exception of the septum. No significant effect on dopamine concentrations in various forebrain regions was found. 3 Acquisition and retention of active avoidance was not altered by the lesion. Marked resistance to extinction was seen when the unconditioned stimulus (shock) was removed. 4 A comparison with work by other authors in which both forebrain noradrenaline and dopamine were depleted suggest that the alteration in extinction seen in both studies is a noradrenergic effect, whereas the deficits in acquisition and retention found previously are dopaminergic in origin.

Acquisition and retention of active avoidance in Xenopus laevis

Adult male South African clawed frogs, Xenopus laevis, were trained in an aquatic shuttlebox on one-way active avoidance of electric shock. Acquisition was observed within daily sessions (30 trials) and between days (4 days). Control groups indicated that learning, rather than pseudoconditioning or sensitization to the CS, was responsible for the observed change in behavior. A retraining measure yielded appreciable savings after a 28-day retention period. Some of the advantages of this species for behavioral research are discussed.

Age effects in the acquisition and retention of active and passive avoidance learning by rats

AbstractThree groups of 8 male albino rats within each of the age ranges 24, 50, and 100 days were trained on an active avoidance task to a criterion of 10 successive avoidances. The number of trials to criterion was found to be a monotonic function of age. One group at each age was tested immediately thereafter for passive avoidance of the conditioning chamber, another group was tested for passive avoidance after 25 days, and the third was tested for retention of active avoidance after 25 days. Groups at 50, 75, and 125 days were used as controls for the active avoidance retention groups. All animals took significantly fewer trials to relearn the active avoidance after 25 days than did controls on the acquisition of the original learning task. On passive avoidance 24‐day olds performed less efficiently than the older groups and failed to show any retention after 25 days.