Involvement of dorsal hippocampal nicotinic receptors in the effect of morphine on memory retrieval in passive avoidance task

Khajehpour, Lotfollah; Rezayof, Ameneh; Zarrindast, Mohammad‐Reza

doi:10.1016/j.ejphar.2008.02.030

Cited by 31 publications

(9 citation statements)

References 63 publications

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“…As described in our previous experiments, nimodipine prevented memory labilization and consequently the endogenous updating. In addition, we reproduced the state-dependent phenomenon and the amnestic pre-test morphine administration reported in other studies (Khajehpour et al 2008). These results confirm that endogenous updating with morphine is dependent on memory reconsolidation.…”

Section: Cfcsupporting

confidence: 67%

Reconsolidation may incorporate state-dependency into previously consolidated memories

et al. 2013

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Some memories enter into a labile state after retrieval, requiring reconsolidation in order to persist. One functional role of memory reconsolidation is the updating of existing memories. There are reports suggesting that reconsolidation can be modulated by a particular endogenous process taking place concomitantly to its natural course, such as water or sleep deprivation. Here, we investigated whether an endogenous process activated during a natural/physiological experience, or a pharmacological intervention, can also contribute to memory content updating. Using the contextual fear conditioning paradigm in rats, we found that the endogenous content of an aversive memory can be updated during its reconsolidation incorporating consequences of natural events such as water deprivation, transforming a previously stored memory into a state-dependent one. This updating seems to be mediated by the activation of angiotensin AT1 receptors in the dorsal hippocampus and local infusion of human angiotensin II (ANGII) was shown to mimic the water deprivation effects on memory reconsolidation. Systemic morphine injection was also able to turn a previously acquired experience into a state-dependent memory, reproducing the very same effects obtained by water deprivation or local angiotensin II infusion, and suggesting that other state-dependent-inducing protocols would also be able to contribute to memory updating. These findings trigger new insights about the influence of ordinary daily life events upon memory in its continuing reconstruction, adding the realm of reconsolidation to the classical view of endogenous modulation of consolidation.

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Section: Cfcsupporting

confidence: 67%

Reconsolidation may incorporate state-dependency into previously consolidated memories

et al. 2013

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“…However, it has been reported that morphine at 5.6mg/kg did not impair performance in a nose-poke repeated performance test (Pitts et al, 2006), and pre-test subcutaneous administration of 5 mg/kg morphine had no effect on memory retrieval in a step-down avoidance test (Lu et al, 2010). Further, post-training administration of 2.5 mg/kg morphine did not significantly reduce step-through latency in a step-through passive avoidance study (Khajehpour et al, 2008). These data suggest that the morphine used in the present study did not interfere with the rats’ associational memory.…”

Section: Discussionmentioning

confidence: 97%

DAMGO in the central amygdala alleviates the affective dimension of pain in a rat model of inflammatory hyperalgesia

Zhang

et al. 2013

Neuroscience

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Pain has sensory-discriminative and emotional-affective dimensions. Recent studies show that the affective component can be assessed with a conditioned place avoidance (CPA) test. We hypothesized that systemic morphine before a post-conditioning test would more potently attenuate the affective aspect compared to the sensory component and that DAMGO, a μ-selective opioid receptor agonist, injected into the central nucleus of the amygdala (CeA) would reduce established CPA. A rat model of inflammatory pain, produced by a complete Freund adjuvant (CFA) injection into the hind paw, was combined with a CPA test. Three experiments were performed on adult male Sprague-Dawley rats. Systemic morphine (0.5 or 1.0 mg/kg) in Experiment 1, intrathecal (i.t.) morphine (2.5 μg/rat) in Experiment 2, and intra-CeA DAMGO (7.7-15.4 ng/0.4μl) in Experiment 3 were given to CFA-injected rats (n=6-8/group) prior to a post-conditioning test. Saline-injected rats were used as control. Time spent in a pain-paired compartment was recorded twice, before conditioning and after a post-conditioning test. Paw withdrawal latency (PWL) to a noxious thermal stimulus was measured before experiment at day −1 and after the post-conditioning test; hyperalgesia was defined as a decrease in PWL. The data showed that CFA-injected rats had significantly negative CPA compared to those of saline-injected rats (P<0.05). Low dosage systemic morphine significantly (P<0.05) reduced CFA-induced CPA but had no effect on PWL. I.t. morphine did not inhibit the display of CPA but significantly increased PWL, suppressing hyperalgesia (P<0.05). Intra-CeA DAMGO significantly inhibited the display of CPA compared to saline (P<0.05) but had no effect on PWL. The data demonstrates that morphine attenuates the affective component more powerfully than it does the sensory and suggests that the sensory and the emotional-affective dimensions are underpinned by different mechanisms.

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“…There appears to be a pharmacological dissociation between lever responding in the initial self-administration phase of the study and responding during the post-6 week drug seeking phase, perhaps suggesting that treatment with BTMPS blunts the effects of contextual cues on drug seeking. Although it has been shown that nAChRs in the VTA as well as the hippocampus are involved in morphine-state-dependent learning and memory retrieval (Khajehpour, et al, 2008; Rezayof, et al, 2008), any effects BTMPS may have on the learning process or encoding of contextual cues will require further investigation.…”

Section: Discussionmentioning

confidence: 99%

The use-dependent, nicotinic antagonist BTMPS reduces the adverse consequences of morphine self-administration in rats in an abstinence model of drug seeking

et al. 2011

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In this study, the use-dependent, nicotinic receptor antagonist bis (2, 2, 6, 6-tetramethyl-4-piperidinyl) sebacate (BTMPS) was evaluated for its ability to attenuate the adverse consequences associated with morphine in rats in all three phases of an abstinence model of drug seeking: self-administration, acute withdrawal, and delayed test of drug seeking. Rats were allowed to self-administer morphine (FR1 schedule) with an active response lever, on a 24hr basis inside operant chambers, for 14 days. Each rat was subsequently evaluated for stereotypical behaviors associated with spontaneous morphine withdrawal. Rats were then placed in standard housing cages for a six week period of protracted abstinence from morphine. After this period, each rat was placed back into its respective operant chamber for a 14 day assessment of unrewarded drug seeking responses. BTMPS was administered to the animals in all three clinically relevant phases in three separate sets of experiments. BTMPS treatment during the self-administration phase resulted in up to a 34% reduction of lever responses to morphine when compared to vehicle treated control animals, as well as a 32% reduction in the dose of morphine self-administered. When given during self-administration and acute withdrawal, BTMPS treatment decreased acute withdrawal symptoms (up to 64%) of morphine use and reduced (up to 45%) drug seeking responses after six weeks of protracted withdrawal compared to control animals. BTMPS treatment after six weeks of abstinence from morphine had no effect. These results offer insight into the role of central cholinergic receptors in the onset and maintenance of drug addiction.

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Involvement of dorsal hippocampal nicotinic receptors in the effect of morphine on memory retrieval in passive avoidance task

Cited by 31 publications

References 63 publications

Reconsolidation may incorporate state-dependency into previously consolidated memories

Reconsolidation may incorporate state-dependency into previously consolidated memories

DAMGO in the central amygdala alleviates the affective dimension of pain in a rat model of inflammatory hyperalgesia

The use-dependent, nicotinic antagonist BTMPS reduces the adverse consequences of morphine self-administration in rats in an abstinence model of drug seeking

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