The beneficial effects of olibanum on memory deficit induced by hypothyroidism in adult rats tested in Morris water maze

The effects of olibanum on male reproductive system damage in a lipopolysaccharide induced systemic inflammation model in rat

Background

Lipopolysaccharide (LPS) as a particle of Gram-negative bacteria is a main contributer in the pathogenesis of the male reproductive system infectious. Male infertility due to LPS is reported to be related to overproduction reactive oxygen species. This study aimed to investigate the effects of olibanum on oxidative stress and apoptosis in testes and sperm dysfunction induced by LPS.

Methods

The male (n = 28) rats were allocated in four groups: control, LPS (1 mg/kg, i.p., 14 days), LPS + Olibanum 100 (100 mg/kg, i.p., 14 days), and LPS + Olibanum 200 (200 mg/kg, i.p., 14 days). Germ cell apoptosis was determined by TUNEL assays and computed using the stereological method. Additionally, semen samples of the animals were analyzed for sperm count and morphology. Oxidative stress indicators were also determined.

Results

The count of TUNEL-positive germ cells in LPS-treated rats was more than that in the controls. Treatment of the animals with olibanum significantly attenuated the number of apoptotic cells compared to the LPS group. The sperm count and those with a normal morphology in LPS-treated rats was lower than that in the controls. Administration of olibanum significantly improved the sperms with normal morphology and sperm count. Olibanum treatment also improved superoxide dismutase, catalase, and total thiol in testicular tissue and decreased malondialdehyde.

Conclusion

Administering both doses of olibanum in LPS-treated rats had potentially a therapeutic value in reducing germ cell apoptosis, as well as improving sperm parameters.

Synaptic Plasticity and Cognitive Ability in Experimental Adult-Onset Hypothyroidism

Adult-onset hypothyroidism impairs normal brain function. Research on animal models of hypothyroidism has revealed critical information on how deficiency of thyroid hormones impacts the electrophysiological and molecular functions of the brain, which leads to the well known cognitive impairment in untreated hypothyroid patients. Currently, such information can only be obtained from experiments on animal models of hypothyroidism. This review summarizes important research findings that pertain to understanding the clinical cognitive consequences of hypothyroidism, which will provide a better guiding path for therapy of hypothyroidism. SIGNIFICANCE STATEMENT: Cognitive impairment occurs during adult-onset hypothyroidism in both humans and animal models. Findings from animal studies validate clinical findings showing impaired long-term potentiation, decreased CaMKII, and increased calcineurin. Such findings can only be gleaned from animal experiments to show how hypothyroidism produces clinical symptoms.

The clinical efficacy of Olibanum gum chewing in patients with Mild-to-Moderate Alzheimer disease: A randomized Parallel-Design controlled trial

BACKGROUND

Alzheimer's disease is a common neurodegenerative disorder in elderly with progressive decline in cognitive functions. This study aimed to investigate the possible memory-improving effects of Olibanum on patients with Alzheimer's disease.

RESEARCH DESIGN AND METHOD

This double-blind, randomized clinical trial was carried out on 72 participants aged 50-75 years. The intervention group (n = 36) received 1.6 g/day of olibanum chewing gum for 18 weeks. The placebo group (n = 36) received chewing gum without olibanum. Neuropsychological assessments were performed at baseline, every 4 weeks, and after 18 weeks of the intervention.

RESULTS

There was no significant difference between (MD: 0.84, 95%CI: -1.10 to 2.78, p = 0.392) at baseline. Both groups had linear improvements over time. There was no significant difference between two groups regarding the improvements after the intervention (F = 0.157, p = 0.693). There were no significant differences between the groups for MMSE score (Mini-Mental State Examination) after the intervention (F = 0.141, p = 0.708).

CONCLUSIONS

This study revealed that 18 weeks of gum chewing with Olibanum did not change the neuropsychological status. More clinical studies are needed to confirm these findings.

Effect of Combined Levothyroxine (L-T4) and 3-Iodothyronamine (T1AM) Supplementation on Memory and Adult Hippocampal Neurogenesis in a Mouse Model of Hypothyroidism

Mood alterations, anxiety, and cognitive impairments associated with adult-onset hypothyroidism often persist despite replacement treatment. In rodent models of hypothyroidism, replacement does not bring 3-iodothyronamine (T1AM) brain levels back to normal. T1AM is a thyroid hormone derivative with cognitive effects. Using a pharmacological hypothyroid mouse model, we investigated whether augmenting levothyroxine (L-T4) with T1AM improves behavioural correlates of depression, anxiety, and memory and has an effect on hippocampal neurogenesis. Hypothyroid mice showed impaired performance in the novel object recognition test as compared to euthyroid mice (discrimination index (DI): 0.02 ± 0.09 vs. 0.29 ± 0.06; t = 2.515, p = 0.02). L-T4 and L-T4+T1AM rescued memory (DI: 0.27 ± 0.08 and 0.34 ± 0.08, respectively), while T1AM had no effect (DI: -0.01 ± 0.10). Hypothyroidism reduced the number of neuroprogenitors in hippocampal neurogenic niches by 20%. L-T4 rescued the number of neuroprogenitors (mean diff = 106.9 ± 21.40, t = 4.99, pcorr = 0.003), while L-T4+T1AM produced a 30.61% rebound relative to euthyroid state (mean diff = 141.6 ± 31.91, t = 4.44, pcorr = 0.004). We performed qPCR analysis of 88 genes involved in neurotrophic signalling pathways and found an effect of treatment on the expression of Ngf, Kdr, Kit, L1cam, Ntf3, Mapk3, and Neurog2. Our data confirm that L-T4 is necessary and sufficient for recovering memory and hippocampal neurogenesis deficits associated with hypothyroidism, while we found no evidence to support the role of non-canonical TH signalling.

The effects of curcumin in learning and memory impairment associated with hypothyroidism in juvenile rats: the role of nitric oxide, oxidative stress, and brain-derived neurotrophic factor

The effect of curcumin (Cur) on cognitive impairment and the possible role of brain tissue oxidative stress, nitric oxide (NO) levels, and brain-derived neurotrophic factor (BDNF) were investigated in juvenile hypothyroid rats. The juvenile rats (21 days old) were allocated into the following groups: (1) control; (2) hypothyroid (0.05% propylthiouracil (PTU) in drinking water); (3-5) hypothyroid-Cur 50, 100, and 150, which in these groups 50, 100, or 150 mg/kg, Cur was orally administered by gavage during 6 weeks. In the hypothyroid rats, the time elapsed and the traveled distance to locate the hidden platform in the learning trials of Morris water maze (MWM) increased, and on the probe day, the amount of time spent in the target quadrant and the distance traveled in there was decreased. Hypothyroidism also decreased the latency and increased the time spent in the darkroom of the passive avoidance (PA) test. Compared with the hypothyroid group, Cur enhanced the performance of the rats in both MWM and PA tests. In addition, Cur reduced malondialdehyde concentration and NO metabolites; however, it increased thiol content as well as the activity of catalase (CAT) and superoxide dismutase enzymes in both the cortex and hippocampus. Cur also increased hippocampal synthesis of BDNF in hypothyroid rats. The beneficial effects of Cur cognitive function in juvenile hypothyroid rats might be attributed to its protective effect against oxidative stress and potentiation of BDNF production.

Boswellic acids ameliorate neurodegeneration induced by AlCl3: the implication of Wnt/β-catenin pathway

Alzheimer's disease (AD) is a neurodegenerative disease (ND) that represents the principal cause of dementia. Effective treatment is still lacking. Without prevention, Alzheimer's disease (AD) incidence is expected to triple within 30 years. The risk increases in highly polluted areas and is positively linked to chronic aluminum (Al) exposure. Canonical Wingless-Int (Wnt)/β-catenin pathway has been found to play a considerable role in ND pathogenesis. Resins of Boswellia serrata (frankincense) have been used traditionally for their psychoactive activity, in addition to their memory-boosting effects. Boswellic acids (BA) are pentacyclic triterpenes. They have antioxidant, anti-inflammatory, antinociceptive, and immunomodulatory activities. This study aimed to elucidate the role of the Wnt/β-catenin pathway in BA protective activity against aluminum-induced Alzheimer's disease. For 6 weeks, rats were treated daily with AlCl3 (100 mg/kg/i.p.) either alone or with BA (125 or 250 mg/kg PO). Results indicated that BA significantly improved learning and memory impairments induced by AlCl3 treatment. Moreover, BA treatment significantly decreased acetylcholinesterase levels and reduced amyloid-beta (Aβ) expression. In addition, BA ameliorated the increased expression of tumor necrosis factor-alpha (TNF-α) and interleukin-1 beta (IL-1β), inhibited lipid peroxidation, and increased total antioxidants in the brain. Indeed, BA significantly suppressed AlCl3-induced decrease of brain-derived neurotrophic factor, pGSK-3β (Ser 9), and β-catenin. BA (250 mg/kg) showed a significant protective effect compared to a lower dose. The results conclude that BA administration modulated the expression of Wnt/β-catenin pathway-related parameters, contributing to BA's role against Al-induced Alzheimer's disease. Effect of Boswellic acids on AlCl3-induced neurodegenerative changes. ChE cholinesterase, Ach acetylcholine, BDNF brain-derived neurotrophic factor, IL-1β interleukin-1β, TNF-α tumor necrosis factor-α.

The Biological Activity of 3-O-Acetyl-11-keto-β-Boswellic Acid in Nervous System Diseases

Frankincense is a hard gelatinous resin exuded by Boswellia serrata. It contains a complex array of components, of which acetyl-11-keto-beta-boswellic acid (AKBA), a pentacyclic triterpenoid of the resin class, is the main active component. AKBA has a variety of physiological actions, including anti-infection, anti-tumor, and antioxidant effects. The use of AKBA for the treatment of mental diseases has been documented as early as ancient Greece. Recent studies have found that AKBA has anti-aging and other neurological effects, suggesting its potential for the treatment of neurological diseases. This review focuses on nervous system-related diseases, summarizes the functions and mechanisms of AKBA in promoting nerve repair and regeneration after injury, protecting against ischemic brain injury and aging, inhibiting neuroinflammation, ameliorating memory deficits, and alleviating neurotoxicity, as well as having anti-glioma effects and relieving brain edema. The mechanisms by which AKBA functions in different diseases and the relationships between dosage and biological effects are discussed in depth with the aim of increasing understanding of AKBA and guiding its use for the treatment of nervous system diseases.

Frankincense diterpenes as a bio-source for drug discovery

INTRODUCTION

Frankincense (Boswellia sp.) gum resins have been employed as an incense in cultural and religious ceremonies for many years. Frankincense resin has over the years been employed to treat depression, inflammation, and cancer in traditional medicines.

AREAS COVERED

This inclusive review focuses on the significance of frankincense diterpenoids, and in particular, incensole derivatives for establishment future treatments of depression, neurological disorders, and cancer. The authors survey the available literature and furnish an overview of future perspectives of these intriguing molecules.

EXPERT OPINION

Numerous diterpenoids including cembrane, prenylaromadendrane, and the verticillane-type have been isolated from various Boswellia resins. Cembrane-type diterpenoids occupy a crucial position in pharmaceutical chemistry and related industries because of their intriguing biological and encouraging pharmacological potentials. Several cembranes have been reported to possess anti-Alzheimer, anti-inflammatory, hepatoprotective, and antimalarial effects along with a good possibility to treat anxiety and depression. Although some slight drawbacks of these compounds have been noted, including the selectivity of these diterpenoids, there is a great need to address these in future research endeavors. Moreover, it is vitally important for medicinal chemists to prepare libraries of incensole-heterocyclic analogs as well as hybrid compounds between incensole or its acetate and anti-depressant or anti-inflammatory drugs.

Molecular evidences on anti-inflammatory, anticancer, and memory-boosting effects of frankincense

Chemical diversity of natural products with drug-like features has attracted much attention from medicine to develop more safe and effective drugs. Their anti-inflammatory, antitumor, analgesic, and other therapeutic properties are sometimes more successful than chemical drugs in controlling disease due to fewer drug resistance and side effects and being more tolerable in a long time. Frankincense, the oleo gum resin extracted from the Boswellia species, contains some of these chemicals. The anti-inflammatory effect of its main ingredient, boswellic acid, has been traditionally used to treat many diseases, mainly those target memory functions. In this review, we have accumulated research evidence from the beneficial effect of Frankincense consumption in memory improvement and the prevention of inflammation and cancer. Besides, we have discussed the molecular pathways mediating the therapeutic effects of this natural supplement.

The Effects of Incensole Acetate on Neuro-inflammation, Brain-Derived Neurotrophic Factor and Memory Impairment Induced by Lipopolysaccharide in Rats

Incensole acetate (IA) is a major component of Boswellia serrata resin that has been shown to have anti-inflammatory, anti-oxidant and neuroprotective properties. The present study determined the effect of IA on lipopolysaccharide (LPS)-induced memory impairment, and hippocampal cytokines and oxidative stress indicators level. We used 32 Wistar rats (220-250 g weight) randomly divided into four groups. The control group, which only received the saline-diluted DMSO (vehicle); LPS group which received LPS and was treated with the vehicle; and two IA-treated groups which received 2.5 or 5 mg/ kg IA before LPS injection. Morris water maze (MWM) and passive avoidance (PA) tests were performed. Finally, the brains were removed and were used to assess cytokines levels and oxidative stress status. Compared to the LPS group, IA administration reduced the time spent and path traveled to reach the hidden platform during 5 days of learning in MWM while increased the time spent in the target quadrant in the probe test. Moreover, IA increased latency while decreased entry number and time spent in the dark chamber of PA test compared to the LPS group. Additionally, pre-treatment with IA attenuated interleukin(IL)-6, tumor necrosis alpha (TNF-α), glial fibrillary acidic protein (GFAP), malondialdehyde (MDA) and nitric oxide (NO) metabolites levels while increased those of IL-10, total thiol, superoxide dismutase (SOD), catalase (CAT) and brain-derived neurotrophic factor (BDNF). Our results indicated that IA improved LPS-induced learning and memory impairments. The observed effects seem to be mediated via a protective activity against neuro-inflammation and brain tissue oxidative damage and through improving BDNF.

Inducible nitric oxide synthase inhibitor, aminoguanidine improved Ki67 as a marker of neurogenesis and learning and memory in juvenile hypothyroid rats

INTRODUCTION

In the present study, the effect of inducible nitric oxide (NO) synthase inhibitor, aminoguanidine (AG) on neurogenesis indicators, learning and memory, and oxidative stress status in juvenile hypothyroid (Hypo) rats was evaluated.

METHOD

The studied groups were including: (a) Control, (b) Hypo, (c-e) Hypo-AG 10, Hypo-AG 20, and Hypo-AG 30. Hypothyroidism was induced in the groups 2-5 by adding propylthiouracil in drinking water (0.05%). AG (10, 20, or 30 mg/kg) was daily injected intraperitoneally in the groups 3-5. The rats of the groups 1 and 2 were injected by saline instead of AG. After 6 weeks treatment, Morris water maze (MMW) and passive avoidance (PA) tests were done. Deep anesthesia was then induced and the brain tissue was excised for biochemical parameters measuring.

RESULTS

Ki67 as a maker of neurogenesis and thiol, superoxide dismutase (SOD), and catalase (CAT) as oxidative stress indicators were decreased in the brain of Hypo group, whereas malondialdehyde (MDA) and NO metabolites were enhanced. AG improved Ki67, thiol, CAT, and SOD while decreased MDA and NO metabolites. The escape latency in the MWM test increased in the Hypo group. The spending time in the target quadrant in the probe test of MWM and step-through latency in the PA test in the Hypo group was lower than Control group. AG reversed all the negative behavioral effects of hypothyroidism.

CONCLUSION

These results revealed that AG improved neurogenesis, learning and memory impairments, and oxidative imbalance in the brain juvenile Hypo rats.

The effects of the combination of Cyperus rotundus, Crocus sativus, Piper nigrum, and Boswellia serrata on learning and memory deficit and oxidative damage in brain tissue of hypothyroid rats

In the present study, the impact of a combination of four memory-enhancer herbs on cognitive impairment and brain tissue oxidative damage due to hypothyroidism was evaluated. Propylthiouracil (PTU; 0.05%) was administrated in drinking water. Rats were treated with a combination of four herbal products (Cyperus rotundus, Crocus sativus, Piper nigrum, and Boswellia serrata) mixed with honey at two doses (640 and 1,280 mg/kg) or donepezil (0.5 mg/kg), for 6 weeks. Memory performance on the Morris water maze (MWM) and avoidance behavior in passive avoidance was impaired by hypothyroidism, and brain tissue oxidative damage occurred. Herbal combination and donepezil significantly improved memory impairment, reduced malondialdehyde concentration, and nitric oxide metabolites while increased the thiol contents and catalase and superoxide dismutase enzymes activity in the brain. Our findings suggest that the mixture of herbal products improves learning and memory deficits caused by hypothyroidism, probably by reducing the brain tissue oxidative damage. PRACTICAL APPLICATIONS: Learning and memory impairment is a common feature of thyroid hormones deficiency. Several studies are showing that hypothyroidism in juvenile and mature rats induces significant cognitive impairment. Likewise, in humans, a close relationship between thyroid hormone deficiency and cognitive impairment has been reported. We used a mixture of herbal products, including Cyperus rotundus, Crocus sativus, Piper nigrum, and Boswellia serrata, to treat hypothyroidism-induced memory impairment. All these herbs are widely used as a food additive across the world. In Iranian traditional medicine, this herbal combination traditionally used to treat cognitive impairments. Numerous studies have indicated that these herbs show neuroprotective and memory-enhancing properties. Our finding indicated that a traditionally used herbal combination could potentially use as a treatment of cognitive impairment induced by thyroid hormone deficiency.

Neuroprotective Effect of Ashwagandha Extract against the Neurochemical Changes Induced in Rat Model of Hypothyroidism

The current aim is to evaluate the effect of ashwagandha root extract (AE) on the neurochemical changes induced in the cortex and hippocampus as a consequence of thyroid dysfunction induced by propylthiouracil (PTU). Male Wistar rats were divided into; control, AE treated rats, rat model of hypothyroidism and rat model of hypothyroidism treated with either AE or L-thyroxine (T4) for 1 month. Rat model of hypothyroidism showed a significant decrease in serum levels of tri-iodothyronine (T3) and T4 and a significant increase in cortical and hippocampal lipid peroxidation (MDA), nitric oxide (NO), superoxide dismutase (SOD) and catalase (CAT). However, reduced glutathione (GSH) decreased significantly. This was associated with a significant increase in hippocampal tumor necrosis factor-α (TNF-α) and cortical dopamine levels. Both L-thyroxine and AE restored T3 and T4 levels. In the hippocampus L-Thyroxine prevented the increase in MDA and restored GSH but failed to restore the increased NO and TNF-α. In the cortex L-thyroxine didn't change the increased MDA and NO and the decreased GSH induced by PTU. L-thyroxine increased cortical and hippocampal SOD and CAT. AE prevented the increased hippocampal MDA, NO and TNF-α and the decreased GSH level induced by PTU. In the cortex AE failed to restore MDA and NO but prevented the decrease in GSH. The increase in cortical dopamine level induced by PTU was ameliorated by L-thyroxine and improved by AE. The present data indicate that AE could prevent thyroid dysfunction and reduce its complications on the nervous system including oxidative stress and neuroinflammation.

Seeing the Unseen of the Combination of Two Natural Resins, Frankincense and Myrrh: Changes in Chemical Constituents and Pharmacological Activities

For the treatment of diseases, especially chronic diseases, traditional natural drugs have more effective therapeutic advantages because of their multi-target and multi-channel characteristics. Among many traditional natural medicines, resins frankincense and myrrh have been proven to be effective in the treatment of inflammation and cancer. In the West, frankincense and myrrh have been used as incense in religious and cultural ceremonies since ancient times; in traditional Chinese and Ayurvedic medicine, they are used mainly for the treatment of chronic diseases. The main chemical constituents of frankincense and myrrh are terpenoids and essential oils. Their common pharmacological effects are anti-inflammatory and anticancer. More interestingly, in traditional Chinese medicine, frankincense and myrrh have been combined as drug pairs in the same prescription for thousands of years, and their combination has a better therapeutic effect on diseases than a single drug. After the combination of frankincense and myrrh forms a blend, a series of changes take place in their chemical composition, such as the increase or decrease of the main active ingredients, the disappearance of native chemical components, and the emergence of new chemical components. At the same time, the pharmacological effects of the combination seem magically powerful, such as synergistic anti-inflammation, synergistic anticancer, synergistic analgesic, synergistic antibacterial, synergistic blood-activation, and so on. In this review, we summarize the latest research on the main chemical constituents and pharmacological activities of these two natural resins, along with chemical and pharmacological studies on the combination of the two.

Effect of 4 weeks of frankincense consumption on explicit motor memory and serum BDNF in elderly men

Background/aim

Memory is a mechanism for coding, storing, and recalling information. Weak memory and learning disability are common psychological problems in the elderly. The aim of this study was to investigate the effect of 4 weeks of frankincense consumption on explicit motor memory and serum BDNF in the elderly.

Materials and methods

Twenty elderly men (mean age of 60.2 ± 1.7 years) were randomly divided into two groups: experimental (n = 12) and placebo (n = 8). The first blood samples were collected 24 h before the pretest. Then both groups participated in a 4-week exercise program based on the protocol of exercising motor memory. During this period, the experimental group received 500-mg frankincense pills two times a day. The second blood sample collection and acquisition test were conducted following the last session of the exercise program. A retention test and a third blood sampling were performed 2 weeks after the last training session. Mixed analysis of variance (2 × 3) for repeated measures was used to analyze the data.

Results

Intergroup comparisons showed that frankincense had a significant effect on the acquisition and retention of explicit motor memory. No difference was observed in serum BDNF between the experimental and placebo groups.

Conclusion

This study revealed that 4 weeks of frankincense consumption facilitates the acquisition and retention of motor memory in older men with moderate mental status.

Adult-Onset Hypothyroidism Alters the Metaplastic Properties of Dentate Granule Cells by Decreasing Akt Phosphorylation

The expression of homosynaptic long-term depression (LTD) governs the subsequent induction of long-term potentiation (LTP) at hippocampal synapses. This process, called metaplasticity, is associated with a transient increase in the levels of several kinases, such as extracellular signal-regulated protein kinases 1/2 (ERK1/2), c-Jun N-terminal kinase (JNK), and Akt kinase. It has been increasingly realized that the chemical changes in the hippocampus caused by hypothyroidism may be the key underlying causes of the learning deficits, memory loss, and impaired LTP associated with this disease. However, the functional role of thyroid hormones in the "plasticity of synaptic plasticity" has only begun to be elucidated. To address this issue, we sought to determine whether the administration of 6-n-propyl-2-thiouracil (PTU) alters the relationship between priming and the induction of subsequent LTP and related signaling molecules. The activation of ERK1/2, JNK, and Akt was measured in the hippocampus at least 95 min after priming onset. We found that priming stimulation at 5 Hz for 3 s negatively impacted the induction of LTP by subsequent tetanic stimulation in hypothyroid animals, as manifested by a more rapid decrease in the fEPSP slope and population spike amplitude. This phenomenon was accompanied by lower levels of phosphorylated Akt in the surgically removed hippocampus of the hypothyroid rats compared to the euthyroid rats. The metaplastic response and the expression of these proteins in the 1-Hz-primed hippocampus were not different between the two groups. These observations suggest that decreased PI3K/Akt signaling may be involved in the compromised metaplastic regulation of LTP observed in hypothyroidism, which may account for the learning difficulties/cognitive impairments associated with this condition.

Adult-onset hypothyroidism increases ethanol consumption

RATIONALE

Only in Europe it can be estimated that more than 20 million of people would be affected by hypothyroidism in some moment of their life. Given that ethanol consumption is so frequent, it would be reasonable to ask what the consequences of ethanol consumption in those individuals affected by hypothyroidism are.

OBJECTIVES

To study the interaction between hypothyroidism and ethanol consumption.

METHODS

We study ethanol consumption in a rat model of methyl-mercaptoimidazole-induced-adult-onset hypothyroidism and thyroid T4/T3 hormone supplementation. Also, we studied the effects of ethanol on motor activity, memory, and anxiety.

RESULTS

We found that hypothyroidism increased the voluntary ethanol consumption and that this was enhanced by thyroid hormone supplementation. Hypothyroidism was associated with motor hyperactivity which was prevented either by T4/T3 supplementation or ethanol. The relationship between hypothyroidism, ethanol, and anxiety was more complex. In an anxiogenic context, hypothyroidism and T4/T3 supplementation would increase immobility, an anxiety-like behavior, while in a less anxiogenic context would decrease rearing, a behavior related to anxiety. Regarding memory, acute ethanol administration did not alter episodic-like memory in hypothyroid rats. Gene expression of enzymes involved in the metabolism of ethanol, i.e., Adh1 and Aldh2, were altered by hypothyroidism and T4/T3 supplementation.

CONCLUSIONS

Our results suggest that hypothyroid patients would need personalized attention in terms of ethanol consumption. In addition, they point that it would be useful to embrace the thyroid axis in the study of ethanol addiction, including as a possible therapeutic target for the treatment of alcoholism and its comorbid disorders.

Feeding Vitamin C during Neonatal and Juvenile Growth Improves Learning and Memory of Rats

We investigated the effects of feeding vitamin C (Vit C) during neonatal and juvenile growth on learning and memory of rats. Rats after delivery were randomly divided into four groups and treated. Group 1, control group, received normal drinking water. Groups 2-4 received Vit C 10, 100, and 500 mg/kg, respectively, from the first day. After 8 weeks, 10 male offspring of each group were randomly selected and tested in the Morris water maze (MWM) and passive avoidance (PA) tests. Finally, the brains were removed for biochemical measurement. In MWM, 10-500 mg/kg Vit C reduced the latency and traveled distance and increased time spent in the target quadrant. In PA, 10 and 100 mg/kg of Vit C increased the latency; 10-500 mg/kg of Vit C decreased the malondialdehyde (MDA) in the brain tissues and increased thiol and catalase (CAT) activity compared to the control group. We showed that feeding rats Vit C during neonatal and juvenile growth has positive effects on learning and memory.

The effects of vitamin E on brain derived neurotrophic factor, tissues oxidative damage and learning and memory of juvenile hypothyroid rats

The effects of vitamin E (Vit E) on brain derived neurotrophic factor (BDNF) and brain tissues oxidative damage as well as on learning and memory impairments in juvenile hypothyroid rats were examined. The rats were grouped as: (1) Control; (2) Propylthiouracil (PTU); (3) PTU-Vit E and (4) Vit E. PTU was added to their drinking water (0.05%) during 6 weeks. Vit E (20 mg/kg) was daily injected (IP). Morris water maze (MWM) and passive avoidance (PA) were carried out. The animals were deeply anesthetized and the brain tissues were removed for biochemical measurements. PTU increased the escape latency and traveled path in MWM (P < 0.001). It also shortened the latency to enter the dark compartment of PA as well as the time spent in the target quadrant in probe trial of MWM (P < 0.01-P < 0.001). All the effects of PTU were reversed by Vit E (P < 0.01-P < 0.001). PTU administration attenuated thiol and BDNF content as well as the activities of superoxide dismutase (SOD) and catalase (CAT) in the brain tissues while increased molondialdehyde (MDA). Moreover, Vit E improved BDNF, thiol, SOD and CAT while diminished MDA. The results of the present study showed that Vit E improved BDNF and prevented from brain tissues oxidative damage as well as learning and memory impairments in juvenile hypothyroid rats.

Comprehensive 2D gas chromatography-time-of-flight mass spectrometry with 2D retention indices for analysis of volatile compounds in frankincense (Boswellia papyrifera)

Frankincense gum resin secreted from Boswellia papyrifera was analysed by comprehensive 2D gas chromatography hyphenated with accurate mass time-of-flight mass spectrometry (GC×GC-accTOFMS). Direct multiple injection experiments with stepwise isothermal temperature programming were then performed to construct isovolatility curves for reference alkane series in GC×GC. This provides access to calculation of second dimensional retention indices (²I). More than 500 peaks were detected and 220 compounds mainly comprising monoterpenes, sesquiterpenes, diterpenes and oxygenated forms of these compounds were identified according to their ¹I, ²I and accurate mass data. The study demonstrates the capability of GC×GC-accTOFMS with retention data on two separate column phases, as an approach for improved component identification. A greater number of identified and/or tentatively identified terpenoids in this traditional Chinese medicine allow for a more comprehensive coverage of the volatile composition of frankincense.

The effect of tablet containing Boswellia serrata and Melisa officinalis extract on older adults' memory: A randomized controlled trial

BACKGROUND

Memory deficits and age-related memory loss are currently two significant concerns in older adults. In Iranian herbal medicine, there are some prescriptions for memory improvement.

OBJECTIVE

This study was designed to investigate the effect of tablet containing Boswellia serrata (BS) extract and Mellisa officinalis (MO) extract on memory of the older adults.

METHOD

This is a randomized, parallel, double-blind, placebo-controlled clinical trial that performed among 70 older adults who referred to healthcare centers of Kashan University of Medical Sciences, Iran. Subjects were randomly assigned to receive either tablets (n = 35) or placebo (n = 35) for a month (n = 30). Data were collected using a demographic questionnaire and the Wechsler Memory Scale-Revised (WMS-R). Data were analyzed using Chi-square, independent-samples t-tests, paired t-test, repeated measure ANOVA, and ANCOVA using SPSS v13.

RESULT

Participants' baseline characteristics were similar in the two groups. The study was completed by 53 participants. However, as the analysis was based on an intention-to treat approach, all 70 older adults were included in the final analysis. Comparison of the two groups with showed that the total scores of the WMS-R and the subscales, including auditory immediate, immediate memory, visual immediate and working memory, were increased after consumption of the containing BS and MO tablets (p < 0.0001).

CONCLUSION

The BS and MO tablet in older adults can be beneficial on improvement of memory. This is still necessary to investigate effects and durability of the tablets on older adults with memory impairments in future studies.

Th e eff ects of Nigella Sativa extract on renal tissue oxidative damage during neonatal and juvenile growth in propylthiouracil-induced hypothyroid rats

OBJECTIVE

We investigated the effects of hydroalcoholic extract of Nigella sativa (NS) on renal tissue oxidative damage associated with propylthiouracil (PTU)-induced hypothyroidism during neonatal and juvenile growth in rats.

METHODS

Pregnant rats were divided into five groups designated as: 1) control; 2) propylthiouracil (PTU); 3) PTU-NS100; 4) PTU-NS200, and 5) PTU-NS400. All mothers except the control group received 0.005% PTU in their drinking water during lactation. Besides PTU, mothers in groups 3-5 received 100, 200, and 400 mg/kg of NS extract. After lactation period, the off spring continued to receive the same experimental treatment for the first 8 weeks of their life. Ten male off springs of each group were randomly selected, blood samples collected, and the kidney tissues removed.

RESULTS

The serum thyroxin concentration in PTU group was lower than control group and improved by extract. PTU increased the renal malondialdehyde (MDA), while reduced the total thiols concentrations and catalase (CAT) and superoxide dismutase (SOD) activity compared to control group. Administration of 200 and 400 mg/kg of NS extract decreased MDA level, while it increased the total thiols and 400 mg/kg increased CAT and SOD activity in renal tissues compared to PTU group. Serum creatinine and blood urea nitrogen (BUN) in PTU group was higher than in comparison with the control group. 400 mg/kg decreased creatinine, but both 200 and 400 mg/kg improved BUN concentration compared to PTU group.

CONCLUSION

The results of this study demonstrate that the hydroalcoholic extract of NS has a protective effect on the renal tissue oxidative damage associated with PTU-induced hypothyroidism during neonatal and juvenile growth in rats.

Contribution of Brain Tissue Oxidative Damage in Hypothyroidism-associated Learning and Memory Impairments

The brain is a critical target organ for thyroid hormones, and modifications in memory and cognition happen with thyroid dysfunction. The exact mechanisms underlying learning and memory impairments due to hypothyroidism have not been understood yet. Therefore, this review was aimed to compress the results of previous studies which have examined the contribution of brain tissues oxidative damage in hypothyroidism-associated learning and memory impairments.

Combined Administration of Melissa officinalis and Boswellia serrata Extracts in an Animal Model of Memory

BACKGROUND

Boswellia serrata and Melissa officinalis is traditionally used for its memory enhancing effects.

OBJECTIVES

In this study, we evaluated the protective effects of combined form of these extracts on memory improvement of scopolamine treated rats by the Morris water maze method.

MATERIALS AND METHODS

Two groups (group 1 and 2) of animals were pretreated with combined extracts of B. serrata and M. officinalis (200, 400 mg/Kg body weight) for four weeks and then, 30 minutes before starting the experiment scopolamine was injected (0.1 mg/kg body weight) intraperitoneally to pretreated animals. The control group was the animals that were injected by scopolamine and pre treated with distilled water (group 3). The normal group was treated with distilled water alone (group 4).

RESULTS

For time spent and distance, there was no substantial difference between groups 1, 2 and 4, while they had statistical difference with group 3 (P = 0.001). The spatial memory evaluation showed no significant difference between treated groups and normal group.

CONCLUSIONS

Therefore, the combination of the two extracts had the ability to improve memory as its traditional use.

Boswellia serrata Protects Against Glutamate-Induced Oxidative Stress and Apoptosis in PC12 and N2a Cells

This study was designed to investigate whether the extract from Boswellia serrata oleo-gum resin (BSE) can protect against glutamate-induced oxidative damage and cytotoxicity in PC12 and N2a cell lines. Using a simple and reliable reverse-phase high-performance liquid chromatography (HPLC), the amount of 3-acetyl-11-keto-β-boswellic acid (AKBA) in the BSE was found to be 18.5% w/w. The results confirmed that BSE and AKBA, at concentrations as high as 100 μg/mL or 10 μM, respectively, caused no significant cytotoxicity or apoptotic cell death. Co- and pretreatment with BSE (25-100 μg/mL) or AKBA (5 μM) restored the viability of PC12 and N2a cells under glutamate toxicity (8 mM). Treatment with BSE and AKBA also attenuated the toxic effects of glutamate on intracellular reactive oxygen species, lipid peroxidation, superoxide dismutase activity, and oxidative DNA damage compared with the untreated glutamate-injured cells. Furthermore, BSE and AKBA decreased the apoptotic cell population in the sub-G1 region and the rate of both early and late-stage apoptosis induced by glutamate in the cells. Our data suggest that the protective effects of Boswellia extract and AKBA against glutamate toxicity in PC12 and N2a cells may be mediated through the amelioration of the oxidative stress and the resultant apoptosis.

The effects of Nigella sativa extract on hypothyroidism-associated learning and memory impairment during neonatal and juvenile growth in rats

OBJECTIVES

It has been shown that hypothyroidism-induced oxidative damage in brain tissue is involved in its adverse effects on learning and memory. Nigella sativa (N. sativa) has been suggested to have antioxidant and neuroprotective effects. The objective of this study was to investigate the effects of hydroalcoholic extract of N. sativa on hypothyroidism-associated learning and memory impairment during neonatal and juvenile growth in rats.

METHODS

Thirty pregnant rats were kept in separate cages. After delivery, the mothers and their offspring were randomly divided into six groups including: (1) control, (2) PTU (propylthiouracil), (3) PTU-NS 100, (4) PTU-NS 200, (5) PTU-NS 400, and (6) PTU-Vit C (vitamin C). All dams except the control group received 0.005% PTU in their drinking water during lactation. Besides PTU, dams in groups 3, 4, 5, and 6 received 100, 200, and 400 mg/kg N. sativa extract, or 100 mg/kg Vit C, respectively. After lactation period, pups continued to receive same experimental treatment for the first 8 weeks of their life. Then, 10 male offspring of each group were randomly selected and assessed for the learning and memory abilities by using Morris water maze (MWM) and passive avoidance (PA) tests. Blood samples were collected for thyroxine assessment, animals were euthanized, and the brain tissues were removed and analyzed for total thiol groups and malondialdehyde (MDA) concentrations.

RESULTS

PTU exposure significantly increased the time latency in MWM test, while reduced the time spent in target quadrant, and decreased the latency for entering the dark compartment in PA test. These effects were associated with significant reduction in serum thyroxine levels and brain levels of thiol groups, and significant elevation in hippocampal MDA. Administration of 400 mg/kg N. sativa extract and 100 mg/kg Vit C reduced the time latency, while increased the time spent in target quadrant compared to the PTU group in MWM test. Treatment by 100-400 mg/kg of N. sativa extract and also Vit C significantly increased the time latency for entering the dark compartment in PA test. The serum thyroxine concentrations of the animals treated by all doses of the N. sativa extract as well as by Vit C were higher than that of the PTU group. Two hundred and four hundred milligrams/kilogram of NS extract and 100 mg/kg Vit C decreased the MDA concentration in hippocampal tissues, while increased thiol contents compared to the PTU group.

DISCUSSION

The results of this study demonstrate that the hydroalcoholic extract of N. sativa have protective effects on hypothyroidism-associated learning and memory impairment during neonatal and juvenile growth in rats. The effects were comparable to Vit C and might be due to the protective effects of N. sativa extract against brain tissues' oxidative damage.

Feeding of Nigella sativa during neonatal and juvenile growth improves learning and memory of rats

The positive roles of antioxidants on brain development and learning and memory have been suggested. Nigella sativa (NS) has been suggested to have antioxidant and neuroprotective effects. This study was done to investigate the effects of feeding by the hydro-alcoholic extract of NS during neonatal and juvenile growth on learning and memory of rats. The pregnant rats were kept in separate cages. After delivery, they were randomly divided into four Groups including: (1) control; (2) NS 100 mg/kg (NS 100); (3) NS 200 mg/kg (NS 200); and (4) NS 400 mg/kg (NS 400). Rats in the control group (Group 1) received normal drinking water, whereas Groups 2, 3, and 4 received the same drinking water supplemented with the hydro-alcoholic extract of NS (100 mg/kg, 200 mg/kg, and 400 mg/kg, respectively) from the 1st day after birth through the first 8 weeks of life. After 8 weeks, 10 male offspring from each group were randomly selected and tested in the Morris water maze (MWM) and passive avoidance (PA) test. Finally, the brains were removed and total thiol groups and malondialdehyde (MDA) concentrations were determined. In the MWM, treatment by 400 mg/kg extract reduced both the time latency and the distance traveled to reach the platform compared to the control group (p < 0.05–p < 0.01). Both 200 mg/kg and 400 mg/kg of the extract increased the time spent in the target quadrant (p < 0.05–p < 0.01). In the PA test, the treatment of the animals by 200 mg/kg and 400 mg/kg of NS extract significantly increased the time latency for entering the dark compartment (p < 0.05–p < 0.001). Pretreatment of the animals with 400 mg/kg of NS extract decreased the MDA concentration in hippocampal tissues whereas it increased the thiol content compared to the control group (p < 0.001). These results allow us to propose that feeding of the rats by the hydro-alcoholic extract of NS during neonatal and juvenile growth has positive effects on learning and memory. The effects might be due to the antioxidant effects.

The effects of tamoxifen on learning, memory and brain tissues oxidative damage in ovariectomized and naïve female rats

Background:

Regarding the modulatory effects of tamoxifen (TAM) on the actions of estrogen in the present study, the effects of TAM on learning, memory and brain tissues oxidative damage in ovariectomized (OVX) and naοve female rats was investigated.

Materials and Methods:

The animals were divided into: (1) Sham, (2) OVX, (3) Sham-tamoxifen (Sham-TAM) and (4) ovariectomized-tamoxifen (OVX-TAM). The animals of the Sham-TAM and OVX-TAM groups were treated by TAM (1 mg/kg; 4 weeks).

Results:

In Morris water maze, the escape latency in the OVX group was higher than in the Sham group (P < 0.01). The time latency in the animals of OVX-TAM group was lower than that of OVX group (P < 0.01); however, there were no significant differences between the Sham-TAM and Sham groups. In the probe trial, the time spent in target quadrant (Q₁) by the animals of OVX group was lower than that of Sham group (P < 0.01). Interestingly, the animals of OVX-TAM group spent more times in target quadrant (Q₁) compared with OVX group (P < 0.01). In passive avoidance test, the animals of OVX group had lower latencies to enter the dark compartment compared with the Sham group (P < 0.05). The time latency to enter the dark compartment by animals of OVX-TAM group was higher than in OVX group (P < 0.01). In OVX-TAM group, the total thiol concentration was significantly higher (P < 0.05) and malondialdehyde concentration was lower (P < 0.01) than OVX group.

Conclusions:

These results allow us to propose that TAM enhances learning and memory of OVX rats. The possible mechanism may be due to the protective effects against brain tissues oxidative damage.

Evaluation of developmental toxicity of propylthiouracil and methimazole

BACKGROUND

Propylthiouracil (PTU) and methimazole (MMI) are antithyroid drugs used to treat hyperthyroidism. Despite the widespread use of PTU and MMI during pregnancy, modest clinical data and less animal data are available on the teratogenic potential of these drugs.

METHODS

We evaluated the teratogenicity of in utero exposure to PTU or MMI in mice and rats. First, pregnant C57Bl/6 mice were treated daily with PTU (10 or 100 mg/kg), MMI (2 or 20 mg/kg), or vehicle from gestation day (GD) 6 to 16. GD 18 fetuses were evaluated for gross and histopathological abnormalities. Next, pregnant Sprague-Dawley rats were treated daily with PTU (50 or 100 mg/kg), MMI (10 or 20 mg/kg), or vehicle from GD 6 to 19, followed by evaluation for gross and histopathological abnormalities at GD 20.

RESULTS

In mice treated with PTU or MMI, no significant histopathological abnormalities or external gross malformations, and no adverse effects on placental weight, litter size, resorption rates, or fetal weight were observed at GD 18. In rats, no adverse effects on litter size, placental weights, or maternal body weights were observed with either PTU or MMI treatment. PTU treatment (50 and 100 mg/kg) and MMI (10 mg/kg) treatment resulted in a decrease in crown-rump length in rat fetuses but no external gross malformations or histopathological abnormalities were observed.

CONCLUSION

We did not observe either gross external malformations or histopathological malformations in mice or rats treated long-term with high doses of PTU or MMI during pregnancy.

Frankincense ( rǔ xiāng; boswellia species): from the selection of traditional applications to the novel phytotherapy for the prevention and treatment of serious diseases

Frankincense (乳香 Rǔ Xiāng; Boswellia Species), the resinous extract from the trees of the genus Boswellia, has been used for centuries in cultural ceremonies, as a cosmetic agent, and as a traditional medicine to treat a variety of ailments, especially inflammatory diseases including asthma, arthritis, cerebral edema, chronic pain syndrome, chronic bowel diseases, cancer, and some other illnesses. Boswellic acids are the active compounds of frankincense and AKBA (3-O-acetyl-11-keto-β-boswellic acid) is the most important and effective acid among them. Some studies have shown that the use of frankincense can also improve the learning and enhance the memory in animals and human beings. It seems that frankincense might have a potential ability to be used as an alternative natural medicine not only for chronic and inflammatory diseases but also for brain and memory disorders.

Protective role of endogenous ovarian hormones against learning and memory impairments and brain tissues oxidative damage induced by lipopolysaccharide

BACKGROUND

The contribution of neuroinflammation in Alzheimer's disease (AD) has been widely reported. The effects of female gonadal hormones in both neuroinflammation and brain cognitive functions have also been well considered.

OBJECTIVES

In the present study, the possible protective role for endogenous ovarian hormones against learning and memory impairment as well as brain tissues oxidative damage induced by lipopolysachride (LPS) was investigated in rats.

MATERIALS AND METHODS

THE RATS WERE DIVIDED INTO FOUR GROUPS: Sham-LPS, Ovariectomized (OVX)-LPS, Sham, and OVX. The animals of sham group were in proestrous phase in which the serum concentration of estradiol is high. The Sham-LPS and OVX-LPS groups were treated with LPS (250 µg/kg) before acquisition. The animals were examined using passive avoidance (PA) test. The brains were then removed and malondialdehyde (MDA) and total thiol groups concentrations were measured.

RESULTS

The time latency to enter the dark compartment by OVX-LPS group was shorter than that of OVX at both first and 24th hours after the shock (P < 0.05 - P < 0.001). In Sham-LPS and OVX-LPS groups, total thiol concentration in hippocampal and cortical tissues were significantly lower while MDA concentrations were higher than that of Sham and OVX groups (P < 0.05 - P < 0.001). ). The hippocampal MDA concentration in OVX-LPS group was higher than Sham- LPS group (P < 0.01).

CONCLUSIONS

Brain tissue oxidative damage contributed in deleterious effects of LPS on learning and memory. Some protective effects for the endogenous ovarian hormones against damaging effects of LPS on learning and memory function, as well as brain tissues oxidative damage could be postulated; however, it needs more investigation.

Effects of different extracts of Eugenia caryophyllata on pentylenetetrazole-induced seizures in mice

OBJECTIVE

To investigate the possible anticonvulsant effect of different extracts of Eugenia caryophyllata (clove) on pentylenetetrazole (PTZ)-induced seizures in mice.

METHODS

The animals were divided into saline, 50, 100, 250 and 500 mg/kg of aqueous extract, 50, 100, 250 and 500 mg/kg of ethanolic extract, and 50, 100, 250 and 500 mg/kg of chloroformic extract of clove groups. The extracts or saline were injected 60 min before each PTZ injection. Latency to the first minimal clonic seizure (MCS) and generalized tonic-clonic seizure (GTCS) and the percent of mortality were recorded.

RESULTS

Aqueous extract of clove at doses of 50, 100, 250 and 500 mg/kg significantly extended the MCS and GTCS latency (P<0.05). The MCS latency in mice treated with 50, 100 and 250 mg/kg of the ethanolic extract was significantly increased (P<0.05). The GTCS latency in mice treated with 50, 100, 250 and 500 mg/kg of ethanolic extract was significantly higher than that of the saline-treated group (P<0.05). There were no significant differences in MCS and GTCS latency between mice treated with different chloroformic extract of clove or saline.

CONCLUSION

The aqueous and ethanolic extracts of clove could inhibit the PTZ-induced convulsion, and this plant has the potential to be used as a new therapeutic agent for control of seizures. The exact mechanisms and the active compounds that are responsible for the anticonvulsive effect need to be clarified in future studies.

The effects of olibanum administered to methimazole-treated dams during lactation on learning and memory of offspring rats

The effect of olibanum administered during lactation to methimazole-treated dams on the learning of offspring was evaluated. The animals were treated for 60 days from the first day of lactation period: group 1--tap water, group 2-0.03% methimazole and groups 3 and 4-0.03% methimazole with 0.25% or 0.125% olibanum, respectively. The serum thyroxin level in the offspring of group 2 was significantly lower than that of group 1. However, there was no difference compared to groups 3 and 4. In a Morris water maze, the distance and time latency to reach the platform in offspring of group 2 was significantly higher than groups 1, 3 and 4. In probe trial, the time spent in target quadrant (Q₁) by offspring of group 2 was lower than groups 1, 3 and 4. It is suggested that impaired learning and memory in the offspring of hypothyroid rats may be prevented by olibanum.

Evaluation of systemic administration of Boswellia papyrifera extracts on spatial memory retention in male rats

Time-dependent effects of ethanolic extract of Boswellia papyrifera, administered systemically, on spatial memory retention in the Morris water maze were investigated in male rats. A total extract of Boswellia papyrifera (300 mg/kg) was administered every eight hours to three groups of rats by gavage for 1, 2 and 4 weeks. In a separate set of experiments, three doses of a fraction of the extract, called the boswellic acids (100, 200 and 300 mg/kg) were administered by gavage to three groups of rats three times a day for 2 weeks. Following these applications, animals were trained for 4 days. Behavioral testing for evaluation of spatial memory retention was performed 48 h after completion of training. Boswellia papyrifera extracts and boswellic acids caused a significant reduction in escape latency and distance traveled but had no influence on swimming speed. These findings provide evidence that Boswellia papyrifera extracts affect spatial memory retention irrespective of the treatment period. In addition our data show that systemic administration of the boswellic acids fraction enhanced spatial memory retention in a dose-dependent manner. These improving effects may be due to some extent to the interactions of these products with inflammatory mediators, neurotransmitter signaling cascades or protein kinase pathways in the brain.

Chronic treatment with the nitric oxide synthase inhibitor, L-NAME, attenuates estradiol-mediated improvement of learning and memory in ovariectomized rats

INTRODUCTION

The role of ovarian hormones and nitric oxide in learning and memory has been widely investigated.

OBJECTIVE

The present study was carried out to evaluate the effect of the nitric oxide synthase (NOS) inhibitor, N (G)-nitro-L-arginine methyl ester (L-NAME), on the ability of estradiol to improve learning in OVX rats using the Morris water maze.

METHODS

Forty rats were divided into five groups: (1) ovariectomized (OVX), (2) ovariectomized-estradiol (OVX-Est), (3) ovariectomized-L-NAME 10 (OVX-LN 10), (4) ovariectomized-L-NAME 50 (OVX-LN 50) and (5) ovariectomized-estradiol-L-NAME 50 (OVX-Est-LN 50). The animals in the OVX-Est group were treated with a weekly injection of estradiol valerate (2 mg/kg; i.m.). The OVX-LN 10 and OVX-LN 50 groups were treated with daily injections of 10 and 50 mg/kg L-NAME (i.p.), respectively. The animals in the OVX-Est-LN 50 group received a weekly injection of estradiol valerate and a daily injection of 50 mg/kg L-NAME. After 8 weeks, all animals were tested in the Morris water maze.

RESULTS

The animals in the OVX-Est group had a significantly lower latency in the maze than the OVX group (p<0.001). There was no significant difference in latency between the OVX-LN 10 and OVX-LN 50 groups in comparison with the OVX group. The latency in the OVX-Est-LN 50 group was significantly higher than that in the OVX-Est group (p<0.001).

CONCLUSION

These results show that L-NAME treatment attenuated estradiol-mediated enhancement of spatial learning and memory in OVX rats, but it had no significant effect in OVX rats without estrogen, suggesting an interaction of nitric oxide and estradiol in these specific brain functions.

Nitric oxide contributes to learning and memory deficits observed in hypothyroid rats during neonatal and juvenile growth

INTRODUCTION

Severe cognitive impairment follows thyroid hormone deficiency during the neonatal period. The role of nitric oxide (NO) in learning and memory has been widely investigated.

METHODS

This study aimed to investigate the effect of hypothyroidism during neonatal and juvenile periods on NO metabolites in the hippocampi of rats and on learning and memory. Animals were divided into two groups and treated for 60 days from the first day of lactation. The control group received regular water, whereas animals in a separate group were given water supplemented with 0.03% methimazole to induce hypothyroidism. Male offspring were selected and tested in the Morris water maze. Samples of blood were collected to measure the metabolites of NO, NO2, NO3 and thyroxine. The animals were then sacrificed, and their hippocampi were removed to measure the tissue concentrations of NO2 and NO3.

DISCUSSION

Compared to the control group's offspring, serum thyroxine levels in the methimazole group's offspring were significantly lower (P<0.01). In addition, the swim distance and time latency were significantly higher in the methimazole group (P<0.001), and the time spent by this group in the target quadrant (Q1) during the probe trial was significantly lower (P<0.001). There was no significant difference in the plasma levels of NO metabolites between the two groups; however, significantly higher NO metabolite levels in the hippocampi of the methimazole group were observed compared to controls (P<0.05).

CONCLUSION

These results suggest that the increased NO level in the hippocampus may play a role in the learning and memory deficits observed in childhood hypothyroidism; however, the precise underlying mechanism(s) remains to be elucidated.