Protective role of Eugenol against the destructive effects of lead on conditioned fear memory in male rats with post-traumatic stress disorder-related behavioral traits

Introduction

Post-traumatic stress disorder (PTSD) is a consequence of living in today's stressful society. Patients have difficulty forgetting traumatic events. lead pollution has many effects on the nervous system, one of which is memory and learning disorders. The herbal medicine Eugenol has a beneficial effect on memory.

Aim

This study aims to investigate the protective effect of Eugenol on lead-induced memory impairments in stressed rats.

Methods

In the first experiment, the animals were divided into three groups: SPS+Saline, SPS+Pb, and naïve. The SPS+Saline, SPS+Pb groups received normal saline and lead through gavage for 21 days, while the sham group remained untreated. Rats were subjected to the modified single prolonged stress model. Memory tests were conducted one week later, evaluating freezing levels in three consecutive tests over three days. In the second experiment, rats were divided into a SPS+Pb+Saline and three treatment groups. The SPS+Pb+Saline group received daily saline injections, while the other groups received different doses of Eugenol (25, 50, and 100 mg/kg). Memory tests similar to the first experiment were conducted.

Results

The results showed significantly higher immobility levels in the SPS+Saline and SPS+Pb groups compared to the sham. Additionally, the SPS+Pb group had a significant higher immobility compared to the SPS+Saline group. In the second experiment, the SPS+Pb+EU 25 group showed a significant lower freezing compared to the SPS+Pb+Saline group. Additionally, freezing in the SPS+Pb+EU 50 and SPS+Pb+EU 100 groups was significantly higher than in the SPS+Pb+EU 25 group. The SPS+Pb+EU 50 group showed a significant higher freezing compared to the SPS+Pb+Saline group.

Conclusion

lead acetate exacerbated memory impairments in stressed rats and Eugenol, particularly at a dose of 25 mg/kg, improved these impairments. Therefore, Eugenol has the potential to partially reduce the negative effects of lead on memory in individuals with PTSD.

Intravenous Transplantation of Adipose-Derived Mesenchymal Stem Cells Promoted The Production of Dopaminergic Neurons and Improved Spatial Memory in A Rat Model of Parkinson's Disease

OBJECTIVE

Parkinson's disease (PD) is a neurodegenerative disorder described by the dynamic decline of dopaminergic neurons in the substantia nigra pars compacta (SNpc). Stem cell transplantation is a new therapeutic strategy in the treatment of PD. The objective of the study was to assess the impact of intravenous infusion of adipose-derived mesenchymal stem cells (AD-MSCs) on memory disorder in Parkinsonian rats.

MATERIALS AND METHODS

In this experimental study, male Wistar rats were randomly divided to four groups containing sham, cell treatment, control, and lesion. The cell treatment group received intravenous injection of AD-MSCs 12 days after PD induction by bilateral injection of 6-hydroxydopamine. Four weeks after lesion formation, spatial memory was examined using the Morris water maze (MWM) assessment. The rats' brains were removed and assessed by bromodeoxyuridine (BrdU), tyrosine hydroxylase (TH), and glial fibrillary acidic protein (Gfap) immunostaining.

RESULTS

Statistical analyses revealed a significant addition and reduction in time spent and escape latency in the target quadrant, respectively, in the cell group as compared to the lesion group. Also, BrdU-labeled cells were present in the substantia nigra (SN). The density of TH-positive cells was significantly increased in the AD-MSCs transplantation group as compared to the lesion group, and the density of astrocytes significantly diminished in the AD-MSCs transplantation group as compared to the lesion group.

CONCLUSION

It appears that AD-MSCs treatment for Parkinson's could decrease the density of astrocytes and promote the density of TH-positive neurons. It appears that AD-MSCs could improve spatial memory impairment in PD.

Folic acid attenuated learning and memory impairment via inhibition of oxidative damage and acetylcholinesterase activity in hypothyroid rats

Hypothyroidism has been reported to be associated with cognitive decline. Considering the role of folic acid (FA) in cognitive performance, the present study was designed to investigate the effects of FA on hypothyroidism-induced cognitive impairment, oxidative damage, and alterations in acetylcholinesterase (AChE) activity in rat model of propylthiouracil (PTU)-induced hypothyroidism. In this study, PTU (0.05% in drinking water) and FA (5, 10, and 15 mg/kg, oral gavage) were administered for the rats during 7 weeks. Then, behavioral performance was tested using Morris water maze (MWM) and passive avoidance (PA) tasks. Finally, oxidative stress indicators and AChE activity were assayed in the brain tissues. The impairing effect of hypothyroidism on cognitive performance was markedly alleviated by FA especially at higher doses. In the MWM test, FA reduced escape latency and travelled distance, compared to the non-treated hypothyroid group. In the PA test, latency to enter dark chamber was significantly enhanced by FA compared to the non-treated hypothyroid group (p < 0.05-p < 0.001). Besides, FA attenuated AChE activity and malondialdehyde level but it increased activity of superoxide dismutase enzyme and total thiol content (p < 0.05-p < 0.001). In conclusion, our findings revealed that FA could improve learning and memory ability in hypothyroid rats. The observed protective effects may have been mediated through regulation of oxidative stress and AChE activity.

Quercetin fail to protect against the neurotoxic effects of chronic homocysteine administration on motor behavior and oxidative stress in the adult rat's cerebellum

Homocysteine (Hcy) is an excitatory amino acid that contains thiol group and derives from the methionine metabolism. It increases vulnerability of the neuronal cells to excitotoxic and oxidative damage. This study aimed to investigate the hyperhomocysteinemia (hHcy) effects on rat cerebellum and the possible protective role of quercetin administration in Hcy-treated rats, using behavioral and biochemical analyzes. To this end, the adult male rats were divided randomly into the control group that received vehicle, Hcy group received Hcy (400 μg/kg), Hcy + Que group received Hcy + quercetin (50 mg/kg), quercetin group received quercetin for 14 days. On Day 14 after the final treatment, lipid peroxidation level, the superoxide dismutase (SOD), and glutathione peroxidase (GPx) activities were evaluated in the cerebellum. After completion of treatment, the rat's performance on rotarod and locomotor activity was evaluated. The results showed that Hcy treatment elicited cerebellar lipid peroxidation, impaired locomotor activity and increased latency to fall on the rotarod. Quercetin failed to attenuate significantly motoric impairment, increased significantly the cerebellar lipid peroxidation and GPx activity in the Hcy + Que group. Our results suggest that Hcy induced cerebellar toxicity and quercetin had no significant protective effects against Hcy toxicity in the cerebellum of adult rats.

Effect of WIN55-212-2 and Consequences of Extinction Training on Conditioned Fear Memory in PTSD Male Rats

Introduction

This study investigates the effects of cannabinoid agonist WIN55-212-2 on acquisition and consolidation phases of the fear memory extinction and also on anxiety and motor activity.

Methods

In this study, we used SPS & S model to induce post-traumatic stress disorder. One week after SPS, to establish a conditioned fear memory, rats received an electric foot shock within shock chamber. After 24 h, for extinction training, the rats were placed back to the chamber for 9 min, without receiving any shock. In 3 consecutive days and on days 17, 24 and 37, extinction tests were carried out and the freezing behavior was evaluated. Thirty minutes before the first three extinction tests, animals received IP injections of WIN or vehicle. Anxiety-like behavior examined with elevated plus-maze and motor activity with open field, 32 days after conditioning.

Results

Exaggerated and continued conditioned fear memory observed in SPS & S group compared with shock group. IP injection of a 0.25 mg/kg dose of WIN before extinction training led to reducing fear responses in animals.

Conclusion

IP injection of WIN increased acquisition or consolidation of fear memory extinction. SPS & S caused anxiety and this effect improved by the agonist (0.25 mg/kg).

Maternal administration of melatonin prevents spatial learning and memory deficits induced by developmental ethanol and lead co-exposure

Melatonin is a radical scavenger with the ability to remove reactive oxidant species. There is report that co-exposure to lead and ethanol during developmental stages induces learning and memory deficits and oxidative stress. Here, we studied the effect of melatonin, with strong antioxidant properties, on memory deficits induced by lead and ethanol co-exposure and oxidative stress in hippocampus. Pregnant rats in lead and ethanol co-exposure group received lead acetate of 0.2% in distilled drinking water and ethanol (4g/kg) by oral gavages once daily from the 5th day of gestation until weaning. Rats received 10mg/kg melatonin by oral gavages. On postnatal days (PD) 30, rats trained with six trials per day for 6 consecutive days in the water maze. On day 37, a probe test was done and oxidative stress markers in the hippocampus were evaluated. Results demonstrated lead and ethanol co-exposed rats exhibited higher escape latency during training trials and reduced time spent in target quadrant, higher escape location latency in probe trial test and had significantly higher malondialdehyde (MDA) levels, significantly lower superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx) activities in the hippocampus. Melatonin treatment could improve memory deficits, antioxidants activity and reduced MDA levels in the hippocampus. We conclude, co-exposure to lead and ethanol impair memory and melatonin can prevent from it by oxidative stress modulation.

The combined effects of developmental lead and ethanol exposure on hippocampus dependent spatial learning and memory in rats: Role of oxidative stress

Either developmental lead or ethanol exposure can impair learning and memory via induction of oxidative stress, which results in neuronal damage. we examined the effect of combined exposure with lead and ethanol on spatial learning and memory in offspring and oxidative stress in hippocampus. Rats were exposed to lead (0.2% in drinking water) or ethanol (4 g/kg) either individually or in combination in 5th day gestation through weaning. On postnatal days (PD) 30, rats were trained with six trials per day for 6 consecutive days in the water maze. On day 37, a probe test was done. Also, oxidative stress markers in the hippocampus were also evaluated. Results demonstrated that lead + ethanol co-exposed rats exhibited higher escape latency during training trials and reduced time spent in target quadrant, higher escape location latency and average proximity in probe trial test. There was significant decrease in superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx) activities and increase of malondialdehyde (MDA) levels in hippocampus of animals co-exposed to lead and ethanol compared with their individual exposures. We suggest that maternal consumption of ethanol during lead exposure has pronounced detrimental effects on memory, which may be mediated by oxidative stress.

Unilateral Hypothalamus Inactivation Prevents PTZ Kindling Development through Hippocampal Orexin Receptor 1 Modulation

INTRODUCTION

Epilepsy is a neural disorder in which abnormal plastic changes during short and long term periods lead to increased excitability of brain tissue. Kindling is an animal model of epileptogenesis which results in changes of synaptic plasticity due to repetitive electrical or chemical sub-convulsive stimulations of the brain. Lateral hypothalamus, as the main niche of orexin neurons with extensive projections, is involved in sleep and wakefulness and so it affects the excitability of the brain. Therefore, we investigated whether lateral hypothalamic area (LHA) inactivation or orexin-A receptor blocking could change convulsive behavior of acute and kindled PTZ treated animals and if glutamate has a role in this regard.

METHODS

Kindling was induced by 40 mg/kg PTZ, every 48 hours up to 13 injections to each rat. Three consecutive stages 4 or 5 of convulsive behavior were used to ensure kindling. Lidocaine was injected stereotaxically to inactivate LHA, unilaterally. SB334867 used for orexin receptor 1 (OX1R) blocking administered in CSF.

RESULTS

We demonstrated that LHA inactivation prevented PTZ kindling and hence, excitability evolution. Hippocampal glutamate content was decreased due to LHA inactivation, OX1R antagonist infusion, lidocaine injection and kindled groups. In accordance, OX1R antagonist (SB334867) and lidocaine injection decreased PTZ single dose induced convulsive behavior. While orexin-A i.c.v. infusion increased hippocampal glutamate content, it did not change PTZ induced convulsive intensity.

DISCUSSION

It is concluded that LHA inactivation prevented kindling development probably through orexin receptor antagonism. CSF orexin probably acts as an inhibitory step on convulsive intensity through another unknown process.

Riluzole Ameliorates Harmaline-induced Tremor in Rat

INTRODUCTION

Excessive olivo-cerebellar burst-firing occurs during harmaline-induced tremor. We hypothesized that antiglutamatergic agents would suppress harmaline tremor. From this point of view, the aim of the present study was to investigate the effects of riluzole on harmaline-induced tremor in rat.

METHODS

Four groups of Wistar rats weighing 80-100 g were injected with harmaline (30 mg/ kg i.p.) for inducing experimental tremors. The rats in group 1 served as control, whereas the animals in groups 2, 3 and 4 were also given riluzole intraperitonealy at doses of 2, 4 and 8 mg/ kg 30 min before and 90 min after harmaline administration. The onset latency, intensity and duration of tremor were recorded.

RESULTS

The results of this study demonstrated that riluzole could significantly increase latency period, and reduce duration and intensity of tremor.

DISCUSSION

It is concluded that pretreatment of riluzole can ameliorate harmaline-induced tremor in rats.

Stress during first pregnancy increases seizure threshold in adult male offspring

OBJECTIVE(S)

Stress induces many homeostatic aberrations which are followed by lifelong allostatic responses. Epilepsy is developed or influenced by different environmental factors, i.e. prenatal stress which makes many contradictory developmental changes in seizure threshold and intensity. We investigated the potential seizure response of the rat offspring to prenatal stress; the stress which was applied to their mothers.

MATERIALS AND METHODS

Nine day heterogeneous sequential stress (HSS) model was used before and during the first and before the second pregnancy. The kindling was induced using 13 IP injections of pentylenetetrazol (PTZ) every 48 hr to adult male Wistar rat's offspring.

RESULTS

The results of the present study demonstrated that, before pregnancy stress decreased the rate of kindling (P<0.05) in the offspring, while stress which was applied during pregnancy completely prevented kindling (P <0.001). Further, their convulsive latency was increased and tonic clonic seizure duration was decreased. In contrast, previous pregnancy and between pregnancies stress could not change kindling process. Although maternal separation stress did not change kindling development, it could increase convulsive intensities by elongating the duration of seizures (P<0.05) and reducing convulsion latency (P <0.05).

CONCLUSION

It is concluded that stress detrimental effects could be prevented by stress which was applied around first pregnancy; however this beneficial effect is weakened by before second pregnancy stress.

Systemic administrations of β-estradiol alleviate both conditioned and sensitized fear responses in an ovariectomized rat model of post-traumatic stress disorder

Although no single widely accepted animal model of PTSD has been established to date, the single prolonged stress (SPS) animal model has been partially validated as a model for PTSD. SPS rats mimic the pathophysiological abnormalities and behavioral characteristics of PTSD, such as enhanced fear response to the traumatic cue (conditioned fear response) and hyper arousal (the sensitized fear response). In the present study we are looking at PTSD-like symptoms in rats. We examined whether Systemic administrations of β-estradiol could alleviate PTSD-like symptoms that are induced by SPS model. In this study, electric foot shocks (two 4s, 1mA with an interval of 30s) were given to Adult ovariectomized rats 1day after SPS procedures. Additionally, β-estradiol (45, 90, and 180μg/kg) or sesame oil (vehicle) were injected immediately after foot shock and before Tests 2 and 3. After different incubation times, one (Test 1), two (Test 2), and three (Test 3) weeks later, the conditioned or sensitized fear responses were measured (Percent of freezing during test) by re-exposing the stressed rats to the shock chamber or a neutral tone in a novel environment. Three other groups were shock, control and sham groups. Ovariectomized rats of Shock group received shocks conducted through the procedure described below on. Animals in control (Ovariectomized rats) and Sham groups (Only submitted to surgery without removal of the ovaries), neither were exposed to the SPS procedure nor received an electrical shock. Also, these three groups were tested for fear responses three times. Findings indicated that rats who received electric shock the day after SPS exhibited both enhanced conditioned and sensitized fear responses in comparison to the control group. β-estradiol in 45μg/kg dose could reduce both types of fear responses. β-estradiol exert an inhibitory influence on contextual fear conditioning (hippocampal-dependent) and on sensitized fear conditioning (amygdala-dependent). Single injection of this dose is enough for CFR alleviation but at least twice injections are necessary to reduce sensitized fear response. Overall our data demonstrate that multiple injections of β-estradiol, dose dependently, could alleviate both SPS induced conditioned and sensitized fear responses, as signs of PTSD.

Role of Oxidative Stress in Ethanol-induced Neurotoxicity in the Developing Cerebellum

OBJECTIVE(S)

The purpose of this study was to investigate the role of oxidative stress in Purkinje cell neurotoxicity of ethanol-treated rat.

MATERIALS AND METHODS

Male rat pups 4-day-old was used in this study. Ethanol was administered to rat pups at a dose of 6 g/kg from postnatal days (PDs) 4 to 5. Pups were killed 90 min after the second alcohol treatment on PD 5 by decapitation and the brain was immediately removed. The cerebellum was dissected for analyzing the oxidative stress parameters and histological study. The activities of several antioxidant enzymes including superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPx) in vermis of cerebellum were assayed. Thiobarbituric acid reactive substances (TBARS) levels were also measured as a marker of lipid peroxidation.

RESULTS

Administration of ethanol significantly increased TBARS levels in the cerebellum compared to control pups (P< 0.01). The treated pups with ethanol exhibited a marked decrease in the GPx activity (P< 0.01) whereas, in spite of decrease in the activities of SOD and CAT, when compared to control, there were not significant differences. The spherical cell bodies of Purkinje cells in control rats are aligned nicely between the granular and molecular layers. In ethanol treated pups, Purkinje cells scattered within the Purkinje cell layer and shrinkage of the cell somata is seen.

CONCLUSION

The results of the present work demonstrated that ethanol exposure during the vulnerable window could increase TBARS levels (lipid peroxidation) and decrease GPx levels in pup's cerebellum. Also, the results confirmed ethanol-induced microencephaly, cerebellar Purkinje cell loss. These findings suggest that Purkinje cell loss is, in part through decrease in the activity of GPx and increase of lipid peroxidation in the rat cerebellum.

Ethanol disrupts reactivated contextual conditioned fear memory: behavioral and histological perspectives

OBJECTIVE

This research study is an attempt to examine whether the administration of ethanol after memory reactivation would modulate subsequent expression of memory in rats. Additionally, we examined whether this administration alters the density of Cornu Ammonis (CA)1 and CA3 pyramidal and dentate gyrus (DG) granule cells.

MATERIALS AND METHODS

In this experimental study, adult male Wistar rats (200-300 g) were trained in a fear conditioning system using two 1 second, 0.6 mA shocks with an interval of 180 seconds. Twenty four hours later rats were returned to the chamber for 120 seconds. Immediately after reactivation they were injected with ethanol (0.5, 1, 1.5 mg/ kg) or saline. 1, 7 and 14 days after reactivation, rats were returned to the context for 5 minutes. Seconds of freezing (absence of all movement except respiration) were scored. In the second experiment (described in the previous paragraph), after test 1, animals were anesthetized with sodium pentobarbital and perfused transcardially with phosphate buffer (10 minutes) and 4% paraformaldehyde (15 minutes). The brains were postfixed in phosphate-buffered 4% paraformaldehyde (24 hours) and 30% sucrose. 10-µm sections were stained with cresyl violet. Data were analyzed by 1-and 2-way ANOVA for repeated measurements by means of SPSS 16.0. Tukey's post hoc test was performed to determine the source of detected significant differences. P <0 .05 were considered significant. Data are presented as mean ± SEM.

RESULTS

Findings from the first experiment indicated that ethanol at a dose of 1.5 mg/kg significantly impaired recall of memory only in the first test. The density of CA1 and CA3 pyramidal and DG granule cells in the ethanol group was decreased (p< 0.01) compared with control group respectively 43.7%, 35.8%, and 37.8.

CONCLUSION

The data demonstrate that ethanol exposure impairs post retrieval processes. Moreover, ethanol decreases the density of CA1, CA3 and DG cells. Presumably it would be a correlation between our behavioral and histological results.

Neuroprotective effects of the 17β-estradiol against ethanol-induced neurotoxicity and oxidative stress in the developing male rat cerebellum: biochemical, histological and behavioral changes

During particular periods of central nervous system (CNS) development, exposure to ethanol can decrease regional brain growth and can result in selective loss of neurons. Unfortunately, there are few effective means of attenuating damage in the immature brain. In this study, the possible antioxidant and neuroprotective properties of 17β-estradiol against ethanol-induced neurotoxicity was investigated. 17β-estradiol (600 μg/kg) was injected subcutaneously in postnatal day (PD) 4 and 5, 30 min prior to intraperitoneal injection of ethanol (6g/kg) in rat pups. Ninety minutes after injection of ethanol, the activities of several antioxidant enzymes including superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (Gpx) in vermis of cerebellum were assayed. Thiobarbituric acid reactive substance (TBARS) levels were also measured as a marker of lipid peroxidation. Behavioral studies, including rotarod and locomotor activity tests were performed in PD 21-23 and histological study was performed after completion of behavioral measurements in postnatal day 23. The results of the present work demonstrated that ethanol could induce lipid peroxidation, increase TBARS levels and decrease glutathione peroxidase levels in pup cerebellum. We also observed that ethanol impaired performance on the rotarod and locomotor activities of rat pups. However, treatment with 17β-estradiol significantly attenuated motoric impairment, the lipid peroxidation process and restored the levels of antioxidants. Histological analysis also indicated that ethanol could decrease vermis Purkinje cell count and 17β-estradiol prevented this toxic effect. These results suggest that ethanol may induce lipid peroxidation in the rat pups cerebellum while treatment with 17β-estradiol improves motor deficits by protecting the cerebellum against ethanol toxicity.

Pulsed electromagnetic fields accelerate wound healing in the skin of diabetic rats

Delayed wound healing is a common complication in diabetes mellitus. From this point of view, the main purpose of the present study is to investigate the effect of extremely low frequency pulsed electromagnetic fields (ELF PEMFs) on skin wound healing in diabetic rats. In this study, diabetes was induced in male Wistar rats via a single subcutaneous injection of 65 mg/kg streptozocin (freshly dissolved in sterile saline, 0.9%). One month after the induction of diabetes, a full-thickness dermal incision (35 mm length) was made on the right side of the paravertebral region. The wound was exposed to ELF PEMF (20 Hz, 4 ms, 8 mT) for 1 h per day. Wound healing was evaluated by measuring surface area, percentage of healing, duration of healing, and wound tensile strength. Obtained results showed that the duration of wound healing in diabetic rats in comparison with the control group was significantly increased. In contrast, the rate of healing in diabetic rats receiving PEMF was significantly greater than in the diabetic control group. The wound tensile strength also was significantly greater than the control animals. In addition, the duration of wound healing in the control group receiving PEMF was less than the sham group. Based on the above-mentioned results we concluded that this study provides some evidence to support the use of ELF PEMFs to accelerate diabetic wound healing. Further research is needed to determine the PEMF mechanisms in acceleration of wound healing in diabetic rats.

Administration of corticosterone after memory reactivation disrupts subsequent retrieval of a contextual conditioned fear memory: dependence upon training intensity

Reactivation of stabilized memories returns them to a labile state and causes them to undergo extinction or reconsolidation processes. Although it is well established that administration of glucocorticoids after training enhance consolidation of contextual fear memories, but their effects on post-retrieval processes are not known. In this study, we first asked whether administration of corticosterone after memory reactivation would modulate subsequent expression of memory in rats. Additionally, we examined whether this modulatory action would depend upon the strength of the memory. We also tested the effect of propranolol after memory reactivation. Adult male Wistar rats were trained in a fear conditioning system using moderate (0.4 mA) or high shock (1.5 mA) intensities. For reactivation, rats were returned to the chamber for 90 s 24h later. Immediately after reactivation, rats were injected with corticosterone (1, 3 or 10mg/kg) or vehicle. One, 7 and 14 days after memory reactivation, rats were returned to the context for 5 min, and freezing behavior was scored. The findings indicated that corticosterone when injected after memory reactivation had no significant effect on recall of a moderate memory, but it impaired recall of a strong memory at a dose of 3mg/kg. Propranolol (5mg/kg) given after the reactivation treatment produced a modest impairment that persisted over three test sessions. Further, the results showed that corticosterone, but not propranolol deficit was reversed by a reminder shock. These findings provide evidence that administration of glucocorticoids following memory reactivation reduces subsequent retrieval of strong, but not moderate, contextual conditioned fear memory likely via acceleration of memory extinction. On the other hand, propranolol-induced amnesia may result from blockade of reconsolidation process. Further studies are needed to determine the underlying mechanisms.