NMDA receptor adjusted co-administration of ecstasy and cannabinoid receptor-1 agonist in the amygdala via stimulation of BDNF/Trk-B/CREB pathway in adult male rats

The interaction between cannabinoids and long-term synaptic plasticity: A survey on memory formation and underlying mechanisms

Synaptic plasticity, including long-term potentiation (LTP) and long-term depression (LTD), is an essential phenomenon in memory formation as well as maintenance along with many other cognitive functions, such as those needed for coping with external stimuli. Synaptic plasticity consists of gradual changes in the biochemistry and morphology of pre- and postsynaptic neurons, particularly in the hippocampus. Consuming marijuana as a primary source of exocannabinoids immediately impairs attention and working memory-related tasks. Evidence regarding the effects of cannabinoids on LTP and memory is contradictory. While cannabinoids can affect a variety of specific cannabinoid receptors (CBRs) and nonspecific receptors throughout the body and brain, they exert miscellaneous systemic and local cerebral effects. Given the increasing use of cannabis, mainly among the young population, plus its potential adverse long-term effects on learning and memory processes, it could be a future global health challenge. Indeed, the impact of cannabinoids on memory is multifactorial and depends on the dosage, timing, formula, and route of consumption, plus the background complex interaction of the endocannabinoids system with other cerebral networks. Herein, we review how exogenously administrated organic cannabinoids, CBRs agonists or antagonists, and endocannabinoids can affect LTP and synaptic plasticity through various receptors in interaction with other cerebral pathways and primary neurotransmitters.

Dose-dependent manner of luteolin in the modulation of spatial memory with respect to the hippocampal level of HSP70 and HSP90 in sleep-deprived rats

Sleep deprivation (SD) induces a variety of deleterious effects on different cognitive functions such as memory. Elevated neuroinflammation, oxidative stress, and apoptosis, and decreased synaptic plasticity and antioxidant capacity are involved in the deleterious effects of SD on memory. On the other hand, luteolin (a flavonoid compound) has antioxidant, neuroprotective, and anti-inflammatory properties. Also, Heat shock protein 70 (HSP70) and Heat shock protein 90 (HSP90) can be involved in modulating memory. In this study, we aimed to assess the effects of SD and luteolin on spatial learning and memory using Morris Water Maze apparatus in rats, with respect to the level of HSP70 and HSP90 in the hippocampus. Luteolin was injected intracerebroventricular (i.c.v.) at the doses of 0.5, 1, and 2 µg/rat. The results showed that SD impaired spatial memory, while luteolin dose-dependently restored SD-induced spatial memory impairment. SD increased the expression level of HSP90 in the hippocampus, whereas luteolin dose-dependently reversed the effect of SD. Furthermore, SD decreased the expression level of HSP70 protein in the hippocampus, while luteolin dose-dependently reversed the effect of SD. In conclusion, HSP70 and HSP90 may be involved in the deleterious effect of SD on memory, and in the improvement effect of luteolin on memory. This is a novel study reporting novel data and we suggest further detailed studies to better understand the interactions between SD, luteolin, and Heat shock proteins.

Effect of neurotropin on Alzheimer's disease-like changes and cognitive function in rats with chronic cerebral hypoperfusion

Chronic cerebral hypoperfusion (CCH) is a main mechanism of cerebrovascular disease and is associated with various cerebrovascular and neurodegenerative diseases, including Alzheimer's disease. However, treatment of CCH in clinical practice is not ideal, but neurotropin (NTP) has been shown to have a neuroprotective effect. Therefore, this study examined the effect and possible mechanism of NTP in nerve injury caused by CCH. A rat CCH model was established by bilateral common carotid artery occlusion (2VO), and rats were treated with intragastric administration of NTP (200 nu/kg/day) for 28 consecutive days. After treatment, rats were subjected to the Morris water maze and novel object recognition test. Subsequently, an ELISA was applied to detect amyloid-β (Aβ) 1-40 and Aβ1-42 levels in rat hippocampal tissues, quantitative reverse transcription PCR assays were used to detect the mRNA expression levels of brain-derived neurotrophic factor (BDNF) and Trk B, and Western blots were used to detect the protein expression levels of BACE1, tau, p-tau, and protein kinase B (Akt)/glycogen synthase kinase 3β (GSK3β) pathway-related proteins. The rat model of CCH was successfully established by 2VO. Behavioral tests indicated that the cognitive ability of 2VO rats was severely impaired. NTP treatment greatly ameliorated the cognitive disability, reduced Aβ1-40 and Aβ1-42 levels and tau phosphorylation, and upregulated BACE1, Trk B, and BDNF expression in the hippocampus of 2VO rats. Finally, we found that NTP markedly activated Akt/GSK3β pathway activity. NTP can ameliorate cognitive disability in CCH rats possibly by reducing Aβ accumulation and tau phosphorylation in the hippocampus. These effects of NTP may be related to the Akt/GSK3β pathway activation. NTP may be a promising new drug candidate for CCH patients.

Differential roles of NMDAR subunits 2A and 2B in mediating peripheral and central sensitization contributing to orofacial neuropathic pain

The spinal N-methyl-d-aspartate receptor (NMDAR), particularly their subtypes NR2A and NR2B, plays pivotal roles in neuropathic and inflammatory pain. However, the roles of NR2A and NR2B in orofacial pain and the exact molecular and cellular mechanisms mediating nervous system sensitization are still poorly understood. Here, we exhaustively assessed the regulatory effect of NMDAR in mediating peripheral and central sensitization in orofacial neuropathic pain. Von-Frey filament tests showed that the inferior alveolar nerve transection (IANX) induced ectopic allodynia behavior in the whisker pad of mice. Interestingly, mechanical allodynia was reversed in mice lacking NR2A and NR2B. IANX also promoted the production of peripheral sensitization-related molecules, such as interleukin (IL)-1β, tumor necrosis factor (TNF)-α, brain-derived neurotrophic factor (BDNF), and chemokine upregulation (CC motif) ligand 2 (CCL2), and decreased the inward potassium channel (Kir) 4.1 on glial cells in the trigeminal ganglion, but NR2A conditional knockout (CKO) mice prevented these alterations. In contrast, NR2B CKO only blocked the changes of Kir4.1, IL-1β, and TNF-α and further promoted the production of CCL2. Central sensitization-related c-fos, glial fibrillary acidic protein (GFAP), and ionized calcium-binding adaptor molecule 1 (Iba-1) were promoted and Kir4.1 was reduced in the spinal trigeminal caudate nucleus by IANX. Differential actions of NR2A and NR2B in mediating central sensitization were also observed. Silencing of NR2B was effective in reducing c-fos, GFAP, and Iba-1 but did not affect Kir4.1. In contrast, NR2A CKO only altered Iba-1 and Kir4.1 and further increased c-fos and GFAP. Gain-of-function and loss-of-function approaches provided insight into the differential roles of NR2A and NR2B in mediating peripheral and central nociceptive sensitization induced by IANX, which may be a fundamental basis for advancing knowledge of the neural mechanisms' reaction to nerve injury.

Effects of Treadmill Exercise on Social Behavior in Rats Exposed to Thimerosal with Respect to the Hippocampal Level of GluN1, GluN2A, and GluN2B

Thimerosal (THIM) kills brain neurons via induction of apoptosis and necrosis and induces the pathological features of autism spectrum disorder (ASD) in rats. THIM also affects the function of glutamatergic receptors. On the other hand, exercise induces both improvement and impairment effects on memory, depending on intensity, type, and duration. Treadmill exercise can also alter the expression of glutamatergic receptors. In this study, we aimed to investigate the effect of THIM and three protocols of treadmill exercise on social interaction memory and hippocampal expression of GluN1, GluN2A, and GluN2B in rats. THIM was injected intramuscularly at the dose of 300 µg/kg. The three-chamber apparatus was used to evaluate social interaction memory, and western blotting was used to assess protein expression. The results showed that THIM impaired social memory. Exercise 1 impaired social affiliation in controls. Social memory was impaired in all exercise groups of controls. Exercise 1 + 2 impaired social affiliation in THIM rats. Social memory was impaired in all groups of THIM rats. Exercises 2 and 1 + 2 decreased the expression of GluN1, and exercise 1 increased the expression of GluN2A and GluN2B in controls. THIM increased the expression of GluN2B, while exercise 1 reversed this effect. All exercise protocols increased the expression of GluN2A, and exercises 2 and 1 + 2 increased the expression of GluN1 in THIM rats. In conclusion, both THIM and exercise impaired social memory. Of note, the results did not show a separate and influential role for glutamatergic subunits in modulating memory processes following THIM injection or exercise.

Investigating the effect of crocin on memory deficits induced by total sleep deprivation (TSD) with respect to the BDNF, TrkB and ERK levels in the hippocampus of male Wistar rats

BACKGROUND

Sleep deprivation (SD) induces cognitive impairments such as memory deficit. Brain-derived neurotrophic factor (BDNF) is considered as the most critical neurotrophin in the central nervous system that is involved in sleep and memory. The main receptor of BDNF, tropomyosin receptor kinase B (TrkB), is dramatically expressed in the hippocampus. Also, extracellular signal-regulated kinase (ERK) has a significant role in memory function. Crocin is a carotenoid chemical compound and the active component of the flower Crocus sativus L. (saffron) that improves memory function and increases the level of BDNF, TrkB and ERK.

AIMS

In this research, we aimed to investigate the effect of total SD (TSD, 24 h) and crocin on memory performance, and BDNF, TrkB and ERK hippocampal levels.

METHODS

Passive avoidance memory was assessed using step-through, and working memory was measured using Y-maze tasks. The level of proteins in both hemispheres of the hippocampus was evaluated using Western blotting. Crocin was injected intraperitoneally at doses of 1, 5 and 15 mg/kg.

RESULTS

Twenty-four-hour TSD impaired both types of memories and decreased the level of all proteins in both hemispheres of the hippocampus. Crocin at all doses restored TSD-induced memory deficits. Crocin (15 mg/kg) reversed the effect of TSD on levels of all proteins.

CONCLUSIONS

The adverse effect of TSD on the level of proteins in the hippocampus may disrupt synaptic plasticity and transmission, which induces memory impairment. Additionally, the restoration effect of crocin on the decrease in protein levels may be involved in its improvement effect on memory performance.

How do stupendous cannabinoids modulate memory processing via affecting neurotransmitter systems?

In the present study, we wanted to review the role of cannabinoids in learning and memory in animal models, with respect to their interaction effects with six principal neurotransmitters involved in learning and memory including dopamine, glutamate, GABA (γ-aminobutyric acid), serotonin, acetylcholine, and noradrenaline. Cannabinoids induce a wide-range of unpredictable effects on cognitive functions, while their mechanisms are not fully understood. Cannabinoids in different brain regions and in interaction with different neurotransmitters, show diverse responses. Previous findings have shown that cannabinoids agonists and antagonists induce various unpredictable effects such as similar effect, paradoxical effect, or dualistic effect. It should not be forgotten that brain neurotransmitter systems can also play unpredictable roles in mediating cognitive functions. Thus, we aimed to review and discuss the effect of cannabinoids in interaction with neurotransmitters on learning and memory. In addition, we mentioned to the type of interactions between cannabinoids and neurotransmitter systems. We suggested that investigating the type of interactions is a critical neuropharmacological issue that should be considered in future studies.

MeBib Suppressed Methamphetamine Self-Administration Response via Inhibition of BDNF/ERK/CREB Signal Pathway in the Hippocampus

Methamphetamine (MA) is one of the most commonly abused drugs in the world by illegal drug users. Addiction to MA is a serious public health problem and effective therapies do not exist to date. It has also been reported that behavior induced by psychostimulants such as MA is related to histone deacetylase (HDAC). MeBib is an HDAC6 inhibitor derived from a benzimidazole scaffold. Many benzimidazole-containing compounds exhibit a wide range of pharmacological activity. In this study, we investigated whether HDAC6 inhibitor MeBib modulates the behavioral response in MA self-administered rats. Our results demonstrated that the number of active lever presses in MA self-administered rats was reduced by pretreatment with MeBib. In the hippocampus of rats, we also found MA administration promotes GluN2B, an NMDA receptor subunit, expression, which results in sequential activation of ERK/CREB/BDNF pathway, however, MeBib abrogated it. Collectively, we suggest that MeBib prevents the MA seeking response induced by MA administration and therefore, represents a potent candidate as an MA addiction inhibitor.

The fluctuations of metabotropic glutamate receptor subtype 5 (mGluR5) in the amygdala in fear conditioning model of male Wistar rats following sleep deprivation, reverse circadian and napping

Sleep is involved in metabolic system, mental health and cognitive functions. Evidence shows that sleep deprivation (SD) negatively affects mental health and impairs cognitive functions, including learning and memory. Furthermore, the metabotropic glutamate receptor subtype 5 (mGluR5) is a metabolic biomarker, which is affected by various conditions, including stress, sleep deprivation, and cognitive and psychiatric disorders. In this research, we investigated the effect of SD and reverse circadian (RC), and two models of napping (continuous and non-continuous) combined with SD or RC on fear-conditioning memory, anxiety-like behavior and mGluR5 fluctuations in the amygdala. 64 male Wistar rats were used in this study. The water box apparatus was used to induce SD/RC for 48 h, and fear-conditioning memory apparatus was used to assess fear memory. The results showed, fear-conditioning memory was impaired following SD and RC, especially in contextual stage. However, anxiety-like behavior was increased. Furthermore, mGluR5 was increased in the left amygdala more than the right amygdala. Additionally, continuous napping significantly improved fear-conditioning memory, especially freezing behavior. In conclusion, following SD and RC, fear-conditioning memory in contextual stage is more vulnerable than in auditory stage. Furthermore, increase in anxiety-like behavior is related to increase in the activity of left amygdala and mGluR5 receptors.

Oxidative stress enzymes are changed in opioid abusers and multidrug abusers

The current study was designed to measure malondialdehyde level (MDA), super oxide dismutase (SOD) activity and COX-2 protein level in the prefrontal cortex (PFC) of drug-abusers. A total of 101 male drug abusers and 13 control subjects were gathered from the Iranian Legal Medicine center, Kahrizak, Tehran. Kind of death was determined by forensic pathologists, and the kind of drugs of abuse was detected using hair analysis. The medial prefrontal cortex (mPFC), lateral prefrontal cortex (lPFC), and orbitofrontal cortex (OFC) were dissected and were kept at -80 °C, until starting the assays. Our results indicated that the level of MDA was increased in the mPFC, lPFC and OFC of pure-opioid and multi-drug abusers compared with the control group. The SOD activity was reduced in the mPFC, lPFC and OFC of abusers in comparison to the control group. The protein level of COX-2 was decreased in the mPFC and lPFC of multi-drug abusers compared with the control group. This elevation in oxidative stress might be due to the increase of dopamine (as a consequence of drug abuse) or the direct effect of opioids and other drugs of abuse on oxidative agents. Antioxidant agents may be useful in preventing the damaging effect of oxidative agents in the brain of drug-addicted persons.

NMDA receptor subunits change in the prefrontal cortex of pure-opioid and multi-drug abusers: a post-mortem study

Addiction is a chronic relapsing disorder and is one of the most important issues in the world. Changing the level of neurotransmitters and the activities of their receptors, play a major role in the pathophysiology of substance abuse disorders. It is well-established that N-methyl-D-aspartate receptors (NMDARs) play a significant role in the molecular basis of addiction. NMDAR has two obligatory GluN1 and two regionally localized GluN2 subunits. This study investigated changes in the protein level of GluN1, GluN2A, and GluN2B in the prefrontal cortex of drug abusers. The medial prefrontal cortex (mPFC), lateral prefrontal cortex (lPFC), and orbitofrontal cortex (OFC) were dissected from the brain of 101 drug addicts brains and were compared with the brains of non-addicts (N = 13). Western blotting technique was used to show the alteration in NMDAR subunits level. Data obtained using Western blotting technique showed a significant increase in the level of GluN1 and GluN2B, but not in GluN2A subunits in all the three regions (mPFC, lPFC, and OFC) of men whom suffered from addiction as compared to the appropriate controls. These findings showed a novel role for GluN1, GluN2B subunits, rather than the GluN2A subunit of NMDARs, in the pathophysiology of addiction and suggested their role in the drug-induced plasticity of NMDARs.

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.

Morphine exposure before conception affects anxiety-like behavior and CRF level (in the CSF and plasma) in the adult male offspring

It has been proven that exposure to some drugs even before gestation had transgenerational effects. To investigate the changes which induced by parental morphine exposure before gestation; mainly the anxiety-like behavior, Corticotropin Releasing Factor (CRF) level in the CSF and plasma, CRF Receptor 1 (CRFR1), and the level of protein kinase C (PKC-α) were evaluated in the male offspring. Male and female Wistar rats were exposed to morphine for 21 following days. Ten days after last drug exposure, animals were prepared for mating in 4 distinct groups as follow: drug-naïve female and male (used as control), drug-naïve female and morphine-abstinent male, drug-naïve male and morphine-abstinent female, and morphine abstinent male and female. Offspring were subjected to assess anxiety-like behavior (using elevated plus maze test). CSF and plasma were gathered, and the CRF level was evaluated by ELISA. Using real-time PCR, the CRFR1 level in the brain was evaluated. Results showed that anxiety-like behavior increased in the offspring of morphine-abstinent parent(s) compared with the control group. CRF level in the plasma and CSF also increased in the litter of morphine-abstinent parent(s). CRFR1 mRNA level was upregulated in the brain of offspring with one and/or two morphine-abstinent parent(s). Furthermore, the level of PKC-α was decreased in the brain of offspring which had one and/or two morphine-abstinent parent(s). Taken together, our findings indicated that morphine exposure even before gestation induced transgenerational effects via dysregulation of HPA axis which results in anxiety in the adult male offspring.

Acupuncture modulates stress response by the mTOR signaling pathway in a rat post-traumatic stress disorder model

Post-traumatic stress disorder (PTSD) is a psychiatric disease that can form following exposure to a traumatic event. Acupuncture has been proposed as a beneficial treatment for PTSD, but the underlying mechanisms remain unclear. The present study investigated whether acupuncture improves depression- and anxiety-like behaviors induced using a single prolonged stress (SPS) as a PTSD rat model. In addition, we investigated whether the effects were mediated by increased mTOR activity and its downstream signaling components, which contribute to protein synthesis required for synaptic plasticity in the hippocampus. We found that acupuncture at HT8 significantly alleviated both depression- and anxiety-like behaviors induced by SPS in rats, as assessed by the forced swimming, elevated plus maze, and open field tests; this alleviation was blocked by rapamycin. The effects of acupuncture were equivalent to those exerted by fluoxetine. Acupuncture regulated protein translation in the mTOR signaling pathway and enhanced the activation of synaptic proteins, PSD95, Syn1, and GluR1 in the hippocampus. These results suggest that acupuncture exerts antidepressant and anxiolytic effects on PTSD-related symptoms by increasing protein synthesis required for synaptic plasticity via the mTOR pathway in the hippocampus. Acupuncture may be a promising treatment for patients with PTSD and play a role as an alternative PTSD treatment.