Role of dorsal hippocampal orexin-1 receptors in memory restoration induced by morphine sensitization phenomenon

Synergistic antidepressant effects of citalopram and SB-334867 in the REM sleep-deprived mice: Possible role of BDNF

This study was done to evaluate the effect of co-treatment of orexin agents along with citalopram on the modulation of depression-like behavior and the expression of BDNF in the prefrontal cortex (PFC) of sleep-deprived male mice. A sleep deprivation model was performed in which rapid eye movement (REM) sleep was completely prohibited, and non-REM sleep was intensely reduced for 24 h. For drug microinjection, the guide cannula was surgically fixed in the left lateral ventricle of mice. Furthermore, we used the open-field test (OFT), forced swim test (FST), tail suspension test (TST), and splash test for recording depression-like behavior as well as Real-Time PCR amplification for assessing the expression of BDNF in the PFC of REM sleep-deprived mice. Our results revealed that REM sleep deprivation did not change locomotor activity while increased depressive-like behavior in FST, TST, and splash tests. However, the expression of BDNF was decreased in the PFC. Intraperitoneally (i.p.) administration of citalopram induced antidepressant effect in the normal and REM sleep-deprived mice. Moreover, intracerebroventricular (i.c.v.) microinjection of a non-effective dose of SB-334867, an orexin antagonist, potentiated the antidepressant-like effect of citalopram. On the other hand, a non-significant dosage of orexin-1 reversed the antidepressant effect of citalopram in the normal and REM sleep-deprived animals. Furthermore, our results showed that injection of citalopram alone or with SB-334867 increased the mRNA expression level of BDNF in the PFC of REM sleep-deprived mice. These data suggest that REM sleep deprivation interferes with the neural systems underlying the depression-like process and supports a likely interaction of the orexin system with citalopram on the modulation of depression-like behavior in REM sleep-deprived mice.

Hippocampal orexin receptors: Localization and function

Orexin (hypocretin) is secreted from the perifornical/lateral hypothalamus and is well known for sleep regulation. Orexin has two, orexin A and B, transcripts and two receptors, type 1 and 2 (OX1R and OX2R), located in the plasma membrane of neurons in different brain areas, including the hippocampus involved in learning, memory, seizures, and epilepsy, as physiologic and pathologic phenomena. OX1R is expressed in the dentate gyrus and CA1 and the OX2R in the CA3 areas. Orexin enhances learning and memory as well as reward, stress, seizures, and epilepsy, partly through OX1Rs, while either aggravating or alleviating those phenomena via OX2Rs. OX1Rs activation induces long-term changes of synaptic responses in the hippocampus, an age and concentration-dependent manner. Briefly, we will review the localization and functions of hippocampal orexin receptors, their role in learning, memory, stress, reward, seizures, epilepsy, and hippocampal synaptic plasticity.

Curcumin prevents cognitive deficits in the bile duct ligated rats

RATIONALE

Bile duct ligation (BDL) in rodents can cause impaired liver function and cognition deficits. Curcumin has shown a preventive and therapeutic role in memory impairment.

OBJECTIVES

Therefore, this study aimed to explore the effect of curcumin on the performance of male adult Wistar rats that underwent BDL, a model of hepatic encephalopathy (HE) in the Morris water maze (MWM).

METHODS

Four weeks after surgery, sham (manipulation of common bile duct without ligation) and BDL rats underwent the MWM test.

RESULTS

The representative data showed that BDL rats exhibited impairments in spatial learning and reference memory in the MWM compared with the sham rats. Treatment of BDL rats with curcumin (40 mg/kg, i.p., for 4 weeks) prevented these impairments, while it did not affect spatial learning and memory in the sham rats, by itself. Curcumin increased expression levels of the pro-survival B cell lymphoma extra-large (Bcl-xL) gene and two genes involved in mitochondrial function, peroxisome proliferative-activated receptor-γ co-activator 1α (PGC-1α) and mitochondrial transcription factor A (TFAM), in the hippocampus of BDL rats compared with the vehicle-treated sham or BDL rats, while it decreased the pro-apoptotic Bcl-2-associated X protein (Bax) gene expression level. BDL up-regulated Bax and down-regulated TFAM, by itself. Furthermore, curcumin reduced the mRNA level of Bax, while it increased Bcl-2 and TFAM mRNA levels.

CONCLUSIONS

These findings demonstrate the beneficial effect of curcumin on cognitive function in BDL rats of the HE model. The curcumin effect may be related to mitochondrial function improvement in the HE.

Metformin loaded phosphatidylserine nanoliposomes improve memory deficit and reduce neuroinflammation in streptozotocin-induced Alzheimer's disease model

Alzheimer's disease (AD) is closely associated with neuroinflammation development in the brain. Co-delivery of metformin (MET) with phosphatidylserine liposomes neuroprotectant may be beneficial in ameliorating AD-related symptoms like memory impairment and inflammation. Therefore, we aimed to prepare metformin containing phosphatidylserine nanoliposomes formulation (MET-PSL) and to evaluate its effect on rats subjected to AD. Alzheimer's disease model was induced by bilateral intracerebroventricular injection of streptozotocin (3 mg/kg) into rat brains using the stereotactic technique. MET-PSL, MET, and PSL alone were administered intraperitoneally to AD-induced animals and factors including learning and memory storage in addition to cytokine and tissue inflammatory changes were evaluated after a 22-day experiment period. The learning and memory parameters significantly (P < 0.05) improved in AD-rats treated with MET-PSL. Moreover, MET-PSL administration significantly (P < 0.05) decreased cytokine levels of IL1-β, TNF-α, and TGF-β in hippocampal tissues of rats with AD. Histological results indicated a considerable reduction in inflammatory and necrotic neural cells along with significantly (P < 0.05) increased neurogenesis in MET-PSL treated rats. Furthermore, our results showed that MET-PSL formulation could potentially act better than the free form of MET and PSL alone in the recovery process of rats with AD. In general, our data suggest that combination therapy of metformin loaded phosphatidylserine liposomes may enhance the therapeutic performance in AD patients of a clinical study.

Mechanisms of Memory Impairment Induced by Orexin-A via Orexin 1 and Orexin 2 Receptors in Post-traumatic Stress Disorder Rats

Post-traumatic stress disorder (PTSD) patients exhibit abnormal learning and memory. Axons from orexin neurons in the lateral hypothalamus innervate the hippocampus, modulating learning and memory via the orexin 1 and 2 receptors (OX1R and OX2R). However, the role of the orexin system in the learning and memory dysfunction observed in PTSD is unknown. This was investigated in the present study using PTSD animal model-single prolonged stress (SPS) rats. Spatial learning and memory in the rats were evaluated with the Morris water maze (MWM) test; changes in body weight and food intake were recorded to assess changes in appetite; and the expression of orexin-A and its receptors in the hypothalamus and hippocampus was examined and quantified by immunohistochemistry, western blotting and real-time PCR. The results showed that spatial memory was impaired and food intake was decreased in SPS rats; this was accompanied by downregulation of orexin-A in the hypothalamus and upregulation of OX1R and OX2R in the hippocampus and of OX1R in the hypothalamus. Intracerebroventricular administration of orexin-A improved spatial memory and enhanced appetite in SPS rats and partly reversed the increases in OX1R and OX2R levels in the hippocampus and hypothalamus. These results suggest that the orexin system plays a critical role in the memory and appetite dysfunction observed in PTSD.

Potentiation of morphine-induced antinociception by harmaline: involvement of μ-opioid and ventral tegmental area NMDA receptors

RATIONAL

Morphine is one of the most well-known and potent analgesic agents; however, it can also induce various side effects. Thus, finding drugs and mechanisms which can potentiate the analgesic effects of low doses of morphine will be a good strategy for pain management.

OBJECTIVE

The involvement of μ-opioid receptors and ventral tegmental area (VTA) glutamatergic system in harmaline and morphine combination on the nociceptive response were investigated. Also, we examined reward efficacy and tolerance expression following the drugs.

METHODS

Animals were bilaterally cannulated in the VTA by stereotaxic instrument. A tail-flick (TF) apparatus and conditioned place preference (CPP) paradigm were used to measure nociceptive response and rewarding effects in male NMRI mice respectively.

RESULTS

Morphine (2 mg/kg, i.p.) had no effect in TF test. Also, harmaline (1.25 and 5 mg/kg, i.p.) could not change pain threshold. Combination of a non-effective dose of harmaline (5 mg/kg) and morphine (2 mg/kg) produced antinociception and also prevented morphine tolerance but had no effect on the acquisition of CPP. Systemic administration of naloxone (0.5 and 1 mg/kg) and intra-VTA microinjection of NMDA (0.06 and 0.1 μg/mouse) before harmaline (5 mg/kg) plus morphine (2 mg/kg) prevented antinociception induced by the drugs. D-AP5 (0.5 and 1 μg/mouse, intra-VTA) potentiated the effect of low-dose harmaline (1.25 mg/kg) and morphine (2 mg/kg) and induced antinociception. Microinjection of the same doses of NMDA or D-AP5 into the VTA alone had no effect on pain threshold.

CONCLUSION

The findings showed that harmaline potentiated the analgesic effect of morphine and reduced morphine tolerance. Glutamatergic and μ-opioidergic system interactions in the VTA seem to have a modulatory role in harmaline plus morphine-induced analgesia.

The Mechanisms Involved in Morphine Addiction: An Overview

Opioid use disorder is classified as a chronic recurrent disease of the central nervous system (CNS) which leads to personality disorders, co-morbidities and premature death. It develops as a result of long-term administration of various abused substances, along with morphine. The pharmacological action of morphine is associated with its stimulation of opioid receptors. Opioid receptors are a group of G protein-coupled receptors and activation of these receptors by ligands induces significant molecular changes inside the cell, such as an inhibition of adenylate cyclase activity, activation of potassium channels and reductions of calcium conductance. Recent data indicate that other signalling pathways also may be involved in morphine activity. Among these are phospholipase C, mitogen-activated kinases (MAP kinases) or β-arrestin. The present review focuses on major mechanisms which currently are considered as essential in morphine activity and dependence and may be important for further studies.

Effects of Acute and Subchronic Anodal Transcranial Direct Current Stimulation (tDCS) on Morphine-Induced Responses in Hotplate Apparatus

Background:

The endogenous opioid system plays a basic role in pain suppression. The opiate analgesia is the most powerful and useful technique for reducing severe pain in many medical conditions. Transcranial direct current stimulation (tDCS) is a neuromodulator technique by which the cerebral cortex is stimulated with a weak and constant electrical current by the painless and non-invasive method.

Materials and Methods:

In this experimental study, we investigated the effect of tDCS on morphine (1.25, 2.5 and 5 mg/kg)-induced pain responses; as we applied left prefrontal anodal stimulation with 0.2 mA intensity and 20 minutes.

Results:

our results revealed that the acute (One-time electrical stimulation 24 hours after the last administration of morphine three days) and subchronic (three times electrical stimulation; one session/day before each administration of morphine three days) left prefrontal anodal tDCS does not alter pain perception induced by different dose of morphine significantly.

Conclusion:

Finally, our data indicated that there is no potentiated effect between acute tDCS or subchronic tDCS and morphine administration with tested parameters significantly.

Benefit effect of REM-sleep deprivation on memory impairment induced by intensive exercise in male wistar rats: with respect to hippocampal BDNF and TrkB

BACKGROUND

Many factors affect our learning and memory quality, but according to different studies, having a positive or negative impact pertains to their characteristics like intensity or the amount.

PURPOSE

The present study was conducted to investigate the effect of 24-hour REM-sleep deprivation on continuous-high intensity forced exercise-induced memory impairment and its effect on Brain-Derived Neurotrophic Factor (BDNF) and Tyrosine kinase B (TrkB) levels in the hippocampus and Prefrontal Cortex area (PFC).

MATERIAL AND METHODS

Animals were conditioned to run on treadmills for 5 weeks then, were deprived of sleep for 24 h using the modified multiple platforms. The effect of intensive exercise and/or 24-h REM-SD was studied on behavioral performance using Morris Water Maze protocol for 2 days, and BDNF/TrkB levels were assessed in hippocampus and PFC after behavioral probe test using western blotting.

RESULTS

After 5 weeks of intensive exercise and 24-h REM-SD, spatial memory impairment and reduction of BDNF and TrkB levels were found in hippocampus and PFC. 24-h REM-SD improved memory impairment and intensive exercise-induced downregulation of BDNF and TrkB protein levels.

CONCLUSION

The results of the study suggested that sleep deprivation might act as a compensatory factor to reduce memory impairment when the animal is under severe stressful condition.

Brain and Cognition for Addiction Medicine: From Prevention to Recovery Neural Substrates for Treatment of Psychostimulant-Induced Cognitive Deficits

Addiction to psychostimulants like cocaine, methamphetamine, and nicotine poses a continuing medical and social challenge both in the United States and all over the world. Despite a desire to quit drug use, return to drug use after a period of abstinence is a common problem among individuals dependent on psychostimulants. Recovery for psychostimulant drug-dependent individuals is particularly challenging because psychostimulant drugs induce significant changes in brain regions associated with cognitive functions leading to cognitive deficits. These cognitive deficits include impairments in learning/memory, poor decision making, and impaired control of behavioral output. Importantly, these drug-induced cognitive deficits often impact adherence to addiction treatment programs and predispose abstinent addicts to drug use relapse. Additionally, these cognitive deficits impact effective social and professional rehabilitation of abstinent addicts. The goal of this paper is to review neural substrates based on animal studies that could be pharmacologically targeted to reverse psychostimulant-induced cognitive deficits such as impulsivity and impairment in learning and memory. Further, the review will discuss neural substrates that could be used to facilitate extinction learning and thus reduce emotional and behavioral responses to drug-associated cues. Moreover, the review will discuss some non-pharmacological approaches that could be used either alone or in combination with pharmacological compounds to treat the above-mentioned cognitive deficits. Psychostimulant addiction treatment, which includes treatment for cognitive deficits, will help promote abstinence and allow for better rehabilitation and integration of abstinent individuals into society.

The role of calcium-calmodulin-dependent protein kinase II in modulation of spatial memory in morphine sensitized rats

It has been shown that drug addiction and memory system are related but the signaling cascades underlying this interaction is not completely revealed yet. It has been demonstrated that binding of Calcium-calmodulin-dependent protein kinase II (CaMKII) to NMDA receptor is important in the memory process. The main objective of the study was to evaluate the role of CaMKII on the spatial memory of rats which previously were sensitized by morphine. The effect of CaMKII inhibitor (KN-93) on memory changes was investigated by hippocampal microinjection of KN-93 on the morphine-sensitized rats. Also, the role of the NMDA receptor in memory retention by KN-93 on the morphine sensitized rat was investigated with NMDA agonist and antagonist. Sensitization was induced by morphine injection (once daily for 3 days) followed by 5 days free of the drug before the trial phase. For the evaluation of spatial memory, the Morris Water Maze test (MWM) was used. Results showed that pre-trial administration of morphine, induced amnesia in MWM (p < 0.05). Also, three days pretreatment with morphine (20 mg/kg) followed by five days washout period, caused to enhance memory retrieval in confront with a pre-trial challenging dose of morphine (5 mg/kg). In addition, KN-93 administration during induction phase in morphine sensitization phenomena facilitated morphine-induced memory retention. In addition, inhibition of the NMDA receptor and KN-93 during the induction phase did not improve memory. However; intra-CA1 co-administration of KN-93 and NMDA during the induction phase of morphine sensitization resulted in improving spatial memory. It can be concluded that the effect of CaMKII on memory retention in morphine-sensitized rats depends on NMDA receptor.

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: 2016

This paper is the thirty-ninth consecutive installment of the annual review of research concerning the endogenous opioid system. It summarizes papers published during 2016 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.

Orexin/hypocretin treatment restores hippocampal-dependent memory in orexin-deficient mice

Orexin A is produced in neurons of the lateral, perifornical and dorsomedial regions of the lateral hypothalamic area, which then project widely throughout the central nervous system to regulate arousal state, sleep-wake architecture, energy homeostasis and cognitive processes. Disruption of orexin signaling leads to sleep disturbances and increased body mass index, but recent studies also indicate that orexin neuron activation improves learning and memory. We hypothesized that hippocampal orexin receptor activation improves memory. To test this idea, we obtained orexin/ataxin-3 (O/A3) mice, which become deficient in orexin neurons by about 12 weeks of age. We first measured hippocampal orexin receptor 1 (OX1R) gene expression and protein levels, then tested acquisition and consolidation of two-way active avoidance (TWAA) memory, a hippocampal-dependent learning and memory task. Finally, we determined if exogenous intra-hippocampal OXA treatment could reverse cognitive impairment (as determined by TWAA) in OA/3 mice. We showed that OX1R mRNA expression and protein levels were significantly elevated in O/A3 mice, indicating the potential for preserved orexin responsiveness. The O/A3 mice were significantly impaired in TWAA memory vs. control mice, but OXA treatment (both acute and chronic) reversed these memory deficits. These results demonstrate that orexin plays an important role in hippocampal-dependent consolidation of two-way active avoidance memory, and orexin replacement can rescue the cognitive impairment.