Central amygdala nicotinic and 5-HT1A receptors mediate the reversal effect of nicotine and MDMA on morphine-induced amnesia

A novel cholinergic projection from the lateral parabrachial nucleus and its role in methamphetamine-primed conditioned place preference

Drug relapse is a big clinical challenge in the treatment of addiction, but its neural circuit mechanism is far from being fully understood. Here, we identified a novel cholinergic pathway from choline acetyltransferase-positive neurons in the external lateral parabrachial nucleus (eLPB^ChAT) to the GABAergic neurons in the central nucleus of the amygdala (CeA^GABA) and explored its role in methamphetamine priming-induced reinstatement of conditioned place preference. The anatomical structure and functional innervation of the eLPB^ChAT–CeA^GABA pathway were investigated by various methods such as fluorescent micro-optical sectioning tomography, virus-based neural tracing, fibre photometry, patch-clamp and designer receptor exclusively activated by a designer drug. The role of the eLPB^ChAT–CeA^GABA pathway in methamphetamine relapse was assessed using methamphetamine priming-induced reinstatement of conditioned place preference behaviours in male mice. We found that the eLPB^ChAT neurons mainly projected to the central nucleus of the amygdala. A chemogenetic activation of the eLPB^ChAT neurons in vitro or in vivo triggered the excitabilities of the CeA^GABA neurons, which is at least in part mediated via the cholinergic receptor system. Most importantly, the chemogenetic activation of either the eLPB^ChAT neurons or the eLPB^ChAT neurons that project onto the central nucleus of the amygdala decreased the methamphetamine priming-induced reinstatement of conditioned place preference in mice. Our findings revealed a previously undiscovered cholinergic pathway of the eLPB^ChAT–CeA^GABA and showed that the activation of this pathway decreased the methamphetamine priming-induced reinstatement of conditioned place preference.

State-dependent memory and its modulation by different brain areas and neurotransmitters

The state-dependent memory defines as a state that the retrieval of recently obtained information may be potential if the subject exists in a similar physiological situation as for the period of the encoding stage. Studies revealed that exogenous and endogenous compounds could induce state-dependent memory. The state-dependent memory made it probable to differentiate the effects of drugs per se on learning from the effects due to alterations in drug state during the task. Studies proposed the role of regions beyond the limbic formation and illustrated that state-dependent memory produced by various neurotransmitter systems and pharmacological compounds. Our review of the literature revealed that: (a) re-administration of drugs on the same state induce state-dependent memory; (b) many neurotransmitters induce endogenous state-dependent memory; (c) there are cross state-dependent learning and memory between some drugs; (d) some sites of the brain including the CA1 areas of the hippocampus, central nucleus of the amygdala (CeA), septum, ventral tegmental area (VTA), and nucleus accumbens (NAC) are involved in state-dependent memory. See also Figure 1(Fig. 1).

Interactive effects of morphine and nicotine on memory function depend on the central amygdala cannabinoid CB1 receptor function in rats

The present study investigated the possible involvement of the central amygdala (CeA) cannabinoid receptors type-1 (CB1Rs) in the interactive effects of morphine and nicotine on memory formation in a passive avoidance learning task. Our results showed that systemic administration of morphine (3 and 6mg/kg, s.c.) immediately after training phase impaired memory consolidation and induced amnesia. Administration of nicotine (0.3 and 0.6mg/kg, s.c.) before testing phase significantly restored morphine-induced amnesia, suggesting a cross state-dependent learning between morphine and nicotine. The results showed that while the administration of the lower dose of nicotine (0.1mg/kg, s.c.) per se did not induce a significant effect on morphine-induced amnesia, intra-CeA injection of arachidonylcyclopropylamide (ACPA), a cannabinoid CB1 receptor agonist (3 and 4ng/rat), significantly potentiated the nicotine response. Furthermore, the blockade of the CeA cannabinoid CB1 receptors by the injection of AM251 (0.75 and 1ng/rat) reversed the potentiative effect of nicotine (0.6mg/kg, s.c.) on morphine-induced amnesia. It should be considered that bilateral injection of the same doses of ACPA or AM251 (0.5-1ng/rat) into the CeA by itself had no effect on morphine response in a passive avoidance learning task. Confirmed by the cubic interpolation planes, the dose-response data revealed a cross-state-dependent learning between morphine and nicotine which may be mediated by the CeA endocannabinoid system via CB1 receptors.

Endogenous Opiates and Behavior: 2015

This paper is the thirty-eighth consecutive installment of the annual review of research concerning the endogenous opioid system. It summarizes papers published during 2015 that studied the behavioral effects of molecular, pharmacological and genetic manipulation of opioid peptides, opioid receptors, opioid agonists and opioid antagonists. The particular topics that continue to be covered include the molecular-biochemical effects and neurochemical localization studies of endogenous opioids and their receptors related to behavior, and the roles of these opioid peptides and receptors in pain and analgesia, stress and social status, tolerance and dependence, learning and memory, eating and drinking, drug abuse and alcohol, sexual activity and hormones, pregnancy, development and endocrinology, mental illness and mood, seizures and neurologic disorders, electrical-related activity and neurophysiology, general activity and locomotion, gastrointestinal, renal and hepatic functions, cardiovascular responses, respiration and thermoregulation, and immunological responses.

Intra-amygdala microinjections of chlorpheniramine impair memory formation or memory retrieval in anxiety- and fear-mediated models

H1 receptor histaminergic antagonist, chlorpheniramine (CPA) participates in cognitive performance in various animal models. However, little is known regarding the effects of CPA microinjection into the amygdala on emotional behavior. The purpose of this study was to investigate whether CPA microinjection into the amygdala has the same effect on two models, one anxiety- and the other fear-mediated, in various memory stages using the elevated plus maze (EPM) and the inhibitory avoidance task (IAT) tests. Two experiments were performed with seventy-two adult male Swiss mice. Behavioral testing was performed on two consecutive days, and in both experiments, before each trial, the animals received bilateral microinjections of saline (SAL) or CPA (0.16 nmol). The animals were re-exposed to the EPM or IAT 24h after the first trial. Four experimental groups were tested: SAL-SAL, SAL-CPA, CPA-SAL and CPA-CPA. In experiment 1, a decreased open arm exploration (% open arm entries, %OAE and% open arms time, %OAT) for SAL-SAL and SAL-CPA was showed, while these measures did not decrease for the CPA-SAL and CPA-CPA groups in Trial 2. In experiment 2, an increase of retention latency in relation to training 2 for the groups SAL-SAL and CPA-SAL and a significant decrease in latency for the group SAL-CPA was revealed. These results indicate that chlorpheniramine microinjection into the amygdala impairs emotional memory acquisition and/or consolidation in the EPM and retrieval of IAT.

Dorsal hippocampal NMDA receptors mediate the interactive effects of arachidonylcyclopropylamide and MDMA/ecstasy on memory retrieval in rats

A combination of cannabis and ecstasy may change the cognitive functions more than either drug alone. The present study was designed to investigate the possible involvement of dorsal hippocampal NMDA receptors in the interactive effects of arachidonylcyclopropylamide (ACPA) and ecstasy/MDMA on memory retrieval. Adult male Wistar rats were cannulated into the CA1 regions of the dorsal hippocampus (intra-CA1) and memory retrieval was examined using the step-through type of passive avoidance task. Intra-CA1 microinjection of a selective CB1 receptor agonist, ACPA (0.5-4ng/rat) immediately before the testing phase (pre-test), but not after the training phase (post-training), impaired memory retrieval. In addition, pre-test intra-CA1 microinjection of MDMA (0.5-1μg/rat) dose-dependently decreased step-through latency, indicating an amnesic effect of the drug by itself. Interestingly, pre-test microinjection of a higher dose of MDMA into the CA1 regions significantly improved ACPA-induced memory impairment. Moreover, pre-test intra-CA1 microinjection of a selective NMDA receptor antagonist, D-AP5 (1 and 2μg/rat) inhibited the reversal effect of MDMA on the impairment of memory retrieval induced by ACPA. Pre-test intra-CA1 microinjection of the same doses of D-AP5 had no effect on memory retrieval alone. These findings suggest that ACPA or MDMA consumption can induce memory retrieval impairment, while their co-administration improves this amnesic effect through interacting with hippocampal glutamatergic-NMDA receptor mechanism. Thus, it seems that the tendency to abuse cannabis with ecstasy may be for avoiding cognitive dysfunction.

Effects of treatment with estrogen and progesterone on the methamphetamine-induced cognitive impairment in ovariectomized rats

Methamphetamine (METH) is one of the most powerful psychostimulant that leads to long lasting cognitive impairment. Earlier researches demonstrated that ovarian hormones including estrogen and progesterone ameliorate cognitive function against various central nervous system disorders. Moreover, recent studies demonstrate a neuroprotective role against methamphetamine toxicity. In current study the effects of estrogen and progesterone alone or in combination, on spatial learning and memory in METH-exposed ovariectomized (OVX) rats are investigated. Three weeks after ovariectomy, the animals were treated by estrogen (1mg/kg, i.p.) and progesterone (8mg/kg, i.p.) alone and in combination or vehicle during 14 consecutive days. On the 28th day, rats were exposed to a single-day METH regimens (four injections of 6mg/kg, s.c, at 2h intervals) 30min after the hormones treatment. Finally, spatial learning and memory were examined using the Morris water maze 2days after the last treatment. The findings showed that estrogen and progesterone did not have significant effect on spatial learning and memory in non METH-exposed OVX rats. The treatment with estrogen and progesterone alone in METH-exposed rats, significantly improved spatial learning and memory impairment. On the other hand, the cognitive performance of animals that received combination of estrogen plus progesterone in METH-exposed rats did not significantly differ from that of METH-exposed animals that received vehicle injections. Taken together, the present findings suggest that treatment with ovarian hormones can partially improve spatial learning and memory deficits induced by methamphetamine in OVX rats.