Differential expression of entorhinal cortex and hippocampal subfields α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) and N-methyl-D-aspartate (NMDA) receptors enhanced learning and memory of rats following administration of Centella asiatica.

Centella asiatica (CA) is a widely used traditional herb, notably for its cognitive enhancing effect and potential to increase synaptogenesis. The α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptors (AMPARs) and N-methyl-D-aspartate receptors (NMDARs) mediate fast excitatory neurotransmission with key roles in long-term potentiation which is believed to be the cellular mechanism of learning and memory. Improved learning and memory can be an indication to the surface expression level of these receptors. Our previous study demonstrated that administration of CA extract improved learning and memory and enhanced expression of AMPAR GluA1 subunit while exerting no significant effects on GABAA receptors of the hippocampus in rats. Hence, to further elucidate the effects of CA, this study investigated the effects of CA extract in recognition memory and spatial memory, and its effects on AMPAR GluA1 and GluA2 subunit and NMDAR GluN2 A and GluN2B subunit expression in the entorhinal cortex (EC) and hippocampal subfields CA1 and CA3. The animals were administered with saline, 100 mg/kg, 300 mg/kg, and 600 mg/kg of CA extract through oral gavage for 14 days, followed by behavioural analysis through Open Field Test (OFT), Novel Object Recognition Task (NORT), and Morris Water Maze (MWM) and lastly morphological and immunohistochemical analysis of the surface expression of AMPAR and NMDAR subunits were performed. The results showed that 14 days of administration of 600 mg/kg of CA extract significantly improved memory assessed through NORT while 300 mg/kg of CA extract significantly improved memory of the animals assessed through MWM. Immunohistochemical analysis revealed differential modulation effects on the expressions of receptor subunits across CA1, CA3 and EC. The CA extract at the highest dose (600 mg/kg) significantly enhanced the expression of AMPAR subunit GluA1 and GluA2 in CA1, CA3 and EC, and NMDAR subunit GluN2B in CA1 and CA3 compared to control. At 300 mg/kg, CA significantly increased expression of AMPAR GluA1 in CA1 and EC, and GluA2 in CA1, CA3 and EC while 100 mg/kg of CA significantly increased expression of only AMPAR subunit GluA2 in CA3 and EC. Expression of NMDAR subunit GluN2 A was significantly reduced in the CA3 (at 100, 300, and 600 mg/kg) while no significant changes of subunit expression was observed in CA1 and EC compared to control. The results suggest that the enhanced learning and memory observed in animals administered with CA was mainly mediated through increased expression of AMPAR GluA1 and GluA2 subunits and differential expression of NMDAR GluN2 A and GluN2B subunits in the hippocampal subfields and EC. With these findings, the study revealed a new aspect of cognitive enhancing effect of CA and its therapeutic potentials through modulating receptor subunit expression.

Hippocampal amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid GluA1 (AMPA GluA1) receptor subunit involves in learning and memory improvement following treatment with Centella asiatica extract in adolescent rats.

INTRODUCTION: Centella asiatica is an herbal plant that contains phytochemicals that are widely believed to have positive effects on cognitive function. The adolescent stage is a critical development period for the maturation of brain processes that encompass changes in physical and psychological systems. However, the effect of C. asiatica has not been extensively studied in adolescents. The aim of this study was therefore to investigate the effects of a C. asiatica extract on the enhancement of learning and memory in adolescent rats. METHODS: The locomotor activity, learning, and memory were assessed by using open field test and water T-maze test. This study also examined changes in neuronal cell morphology using cresyl violet and apoptosis staining. We also performed immunohistochemical study to analyse the expression of the glutamate AMPA receptor (α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid) GluA1 subunit and the GABA receptor (γ-Aminobutyric Acid) subtype GABAA α1 subunit in the hippocampus of the same animals. RESULTS: We found no significant changes in locomotor activity (p > 0.05). The water T-maze data showed that 30 mg/kg dose significantly (p < 0.05) improved learning, memory, and the memory consolidation phase but had no effect on reversal learning (p > 0.05). Histological data revealed no neuronal morphological changes. Immunohistochemical analysis revealed increased expression of the AMPA GluA1 receptor subunit but there was no effect on GABAA receptor α1 subunit expression in the CA1 and CA2 subregions of the hippocampus. CONCLUSIONS: The C. asiatica extract therefore improved hippocampus-dependent spatial learning and memory in a dose-dependent manner in rats through the GluA1-containing AMPA receptor in the CA1 and CA2 sub regions of the hippocampus.

Subchronic toxicity study of standardized methanolic extract of Mitragyna speciosa Korth in Sprague-Dawley Rats.

Mitragyna speciosa Korth, or better known as ketum, has long been used by traditional folk around Southeast Asia to prevent fatigue from working under hot tropical weather and as a replacement of opium, which can then cause addiction. To date, no findings have been reported of the toxic effect of ketum subchronically (28 days). Hence, the aim of this study was to investigate the toxicity of subchronic effect of standardized methanolic extract of ketum (SMEMS) in Sprague-Dawley rats. Rats were orally administered with 100, 200, and 500 mg/kg of SMEMS for 28 days. Body weights were recorded daily. They were terminated at day 28 to obtain data for hematology, biochemistry, and histopathology of the brain, liver, kidney, lung, heart, sciatic nerve, and spinal cord. The SMEMS affected body weight compared to control group. Biochemistry findings showed that liver and kidney were affected with the abnormal values in AST, creatinine, globulin, glucose, total protein, and urea. However, SMEMS produced toxic effect more to liver, kidney, and lung than other organs as observed histopathologically. The results suggested subchronic exposure of ketum is toxic to the physiology of the animals.

Comparison on the Effects and Safety of Tualang Honey and Tribestan in Sperm Parameters, Erectile Function, and Hormonal Profiles among Oligospermic Males.

Introduction. This study aims to evaluate the effectiveness of Tualang honey on sperm parameters, erectile function, and hormonal and safety profiles. Methodology. A randomized control trial was done using Tualang honey (20 grams) and Tribestan (750 mg) over a period of 12 weeks. Sperm parameters including sperm concentration, motility, and morphology were analyzed and erectile function was assessed using IIEF-5 questionnaire. Hormonal profiles of testosterone, FSH, and LH were studied. The volunteers were randomized into two groups and the outcomes were analyzed using SPSS version 18. Results. A total of 66 participants were involved. A significant increment of mean sperm concentration (P < 0.001), motility (P = 0.015) and morphology (P = 0.008) was seen in Tualang honey group. In Tribestan group, a significant increment of mean sperm concentration (P = 0.007), and morphology (P = 0.009) was seen. No significant differences of sperm concentration, motility, and morphology were seen between Tualang honey and Tribestan group and similar results were also seen in erectile function and hormonal profile. All safety profiles were normal and no adverse event was reported. Conclusion. Tualang honey effect among oligospermic males was comparable with Tribestan in improving sperm concentration, motility, and morphology. The usage of Tualang honey was also safe with no reported adverse event.

Histological changes in male accessory reproductive organs in rats exposed to cigarette smoke and the protective effect of honey supplementation.

The effect of cigarette smoke (CS) on histology of male accessory reproductive organs and the possible protective effect of honey supplementation in rats were investigated in this study. Rats received distilled water, honey, CS exposure or honey plus CS exposure. Honey (1.2 g/kg body weight/day) was administered by gavage and CS exposure (3 times per day) was done in a chamber for 13 weeks. CS exposure significantly increased relative weight of epididymis and ventral prostate. There were also significantly increased number of clear cells and epithelial height of cauda epididymis as well as severe interstitial oedema and decreased epithelial height of prostate gland. However, with the supplementation of honey, these histological changes were significantly reversed suggesting the protective effect of honey against the toxic effect of CS on male accessory reproductive organs in rats.

Antioxidant protective effect of honey in cigarette smoke-induced testicular damage in rats.

Cigarette smoke (CS) can cause testicular damage and we investigated the possible protective effect of honey against CS-induced testicular damage and oxidative stress in rats. CS exposure (8 min, 3 times daily) and honey supplementation (1.2 g/kg daily) were given for 13 weeks. Rats exposed to CS significantly had smaller seminiferous tubules diameter and epithelial height, lower Leydig cell count and increased percentage of tubules with germ cell loss. CS also produced increased lipid peroxidation (TBARS) and glutathione peroxidase (GPx) activity, as well as reduced total antioxidant status (TAS) and activities of superoxide dismutase (SOD) and catalase (CAT). However, supplementation of honey significantly reduced histological changes and TBARS level, increased TAS level, as well as significantly restored activities of GPx, SOD and CAT in rat testis. These findings may suggest that honey has a protective effect against damage and oxidative stress induced by CS in rat testis.