Sumita Halder

Clove Oil Reverses Learning and Memory Deficits in Scopolamine-Treated Mice

The present study was performed to examine the effect of Eugenia caryophyllata (Myrtaceae) on learning and memory, and also evaluate whether it can modulate oxidative stress in mice. Passive avoidance step-down task and elevated plus-maze were used to assess learning and memory in scopolamine-treated mice. Oxidative stress parameters were also assessed in brain samples by estimating the malondialdehyde (MDA) and reduced glutathione (GSH) levels at the end of the study. Scopolamine (0.3 mg/kg, i. p.) produced impairment of acquisition memory as evidenced by a decrease in step-down latency and an increase in transfer latency on day 1, and also impairment of retention of memory on day 2. Pretreatment with clove oil (0.05 mL/kg and 0.1 mL/kg) for 3 weeks significantly reversed the increase in acquisition latency and all the doses (0.025, 0.05, 0.1 mL/kg, i. p.) reversed the increase in retention latency induced by scopolamine (0.3 mg/kg, i. p.) in elevated plus-maze. However, 0.05 mL/kg clove oil attenuated memory deficits in the passive avoidance step-down task. Brain samples showed a significant decrease in MDA levels in the group treated with clove oil (0.05 and 0.025 mL/kg). GSH levels were also increased in clove oil-treated mice though the results were not significant. Thus, it can be concluded that clove oil can reverse the short-term and long-term memory deficits induced by scopolamine (0.3 mg/kg, i. p.) and this effect can, to some extent, be attributed to decreased oxidative stress.

Antagonism of stimulation-produced analgesia by naloxone and N-methyl-D-aspartate: role of opioid and N-methyl-D-aspartate receptors.

The present study aims to investigate the influence of electrical stimulation of periaqueductal gray (PAG) following peripheral nerve injury and its modulation by naloxone and N-methyl-D-aspartate (NMDA). Chronic neuropathic pain was induced by chronic constriction injury of the sciatic nerve, and subsequently a cannula was implanted in the PAG area for the purpose of electrical stimulation and intra-PAG drug administration. Intra-PAG administration of morphine, ketamine, and their combination were found to elicit antinociceptive response on hot-plate test. Electrical stimulation of PAG was also observed to demonstrate decreased pain response on hot-plate test, and this effect was reversed by the administration of naloxone, NMDA, and their combination, when injected into the PAG area. These findings suggest that apart from the opioid receptors, probably NMDA receptors also have a role to play in stimulation-produced analgesia.

Essential oil of clove (Eugenia caryophyllata) augments the humoral immune response but decreases cell mediated immunity.

The present study was undertaken to explore the effect of the essential oil isolated from the buds of Eugenia caryophyllata on some immunological parameters. Humoral immunity was assessed by measuring the hemagglutination titre to sheep red blood cells and delayed type hypersensitivity was assessed by measuring foot pad thickness. Clove oil administration produced a significant increase in the primary as well as secondary humoral immune response. In addition, it also produced a significant decrease in foot pad thickness compared with the control group. Thus, these results suggest that clove oil can modulate the immune response by augmenting humoral immunity and decreasing cell mediated immunity. Copyright

Interaction of morphine and potassium channel openers on experimental models of pain in mice

Combination of opioid and potassium channel openers holds immense potential for the treatment for most acute and chronic pain. Therefore, the study was performed to assess the interaction between morphine and K+‐channel openers. Swiss albino mice of either sex weighing between 25 and 30 g were used for the study. The study assesses the interaction between morphine and K+‐channel openers (cromakalim, diazoxide and minoxidil), when administered intraperitoneally, using formalin and tail‐flick tests in mice. Both morphine and K+‐channel openers produced significant antinociception at higher doses in both the behavioral tests. Lower doses of morphine and K+‐channel openers had no significant effect on tail‐flick latency, while the same drugs had significant antinociceptive effect on formalin test. The combination of lower doses of morphine and K+‐openers was observed to have significant antinociceptive effect in both the behavioral tests. Administration of naloxone prior to morphine or K+‐channel openers antagonized the analgesic effect of morphine but not of K+‐channel openers, whereas prior administration of glibenclamide antagonized the effect of both morphine and K+‐channel openers. The study, therefore, suggests that the common site of action of morphine and K+‐channel openers is at the levels of K+‐channels rather than at the level of receptors. However, such interaction depends on the differential sensitivity to different pain stimulus.

Protective effect of melatonin on propoxur-induced impairment of memory and oxidative stress in rats

Propoxur (a carbamate pesticide) has been shown to adversely affect memory and induce oxidative stress on both acute and chronic exposure. This study was designed to explore the modulation of the effects of propoxur over cognitive function by melatonin (MEL). Cognitive function was assessed using step‐down latency (SDL) on a passive avoidance apparatus, and transfer latency (TL) on an elevated plus maze. Oxidative stress was assessed by examining brain malondialdehyde (MDA) and reduced glutathione (GSH) levels and catalase (CAT) activity. A significant reduction in SDL and prolongation of TL was observed for the propoxur (10 mg/kg/d; p.o.) treated group at weeks 6 and 7 when compared with control. One week treatment with MEL (50 mg/kg/d; i.p.) antagonized the effect of propoxur on SDL, as well as TL. Propoxur produced a statistically significant increase in the brain MDA levels and decrease in the brain GSH levels and CAT activity. Treatment with MEL attenuated the effect of propoxur on oxidative stress. The results of the present study thus show that MEL has the potential to attenuate cognitive dysfunction and oxidative stress induced by toxicants like propoxur in the brain.

Role of NMDA and opioid receptors in neuropathic pain induced by chronic constriction injury of sciatic nerve in rats.

Abstract Background: The efficacy of opioids in neuropathic pain is still controversial. Earlier studies have suggested that N-methyl-D-aspartate (NMDA) receptor binding can be affected by opioids and vice versa. The present study aims to explore the interactions between NMDA and opioid receptors using various combinations of drugs acting on these receptors. Methods: We used an animal model of sciatic nerve ligation to induce neuropathic pain, and a hot-plate test was used to assess pain response. Results: It was observed that NMDA and naloxone increased the pain response. Ketamine reduced the pain response, which was further reduced when ketamine was administered in combination with naloxone, but not with NMDA, thus highlighting the activity of the NMDA receptor system. In addition, morphine was also found to increase latency to hind-paw lick, which was further reduced when given in combination with naloxone. Furthermore, triple drug combinations using ketamine+morphine+naloxone and ketamine+NMDA+naloxone demonstrated some significant interactions at these receptors. Conclusions: Thus, our study establishes that neuropathic pain can probably be overcome using higher doses of opioids, and there exists some intimate relationships between NMDA and opioid systems that lead to pain modulation.

Aloe vera improves memory and reduces depression in mice.

Abstract Objective Aloe vera (barbadensis Mill., Family Liliaceae) since ancient times has been used for the treatment of skin disorders, infection, and as a laxative. The present study was undertaken to explore the effect of A. vera (Family Liliaceae) in animal models of learning and memory, depression, and locomotion. Methods To assess learning and memory, the passive avoidance task and elevated plus-maze were used. For evaluating depression, the forced swim test and tail suspension test were performed, and to assess locomotor activity, the rota rod test and photoactometer were used. Results A. vera (200 and 400 mg/kg, p.o.) was found to significantly increase the acquisition and retention step-down latency as compared to control in the passive avoidance task. In the elevated plus-maze, the highest administered dose (400 mg/kg, p.o.) of A. vera significantly reduced the transfer latency as compared to control. The forced swim test as well as tail suspension test showed that A. vera at all administered doses (100, 200, and 400 mg/kg, p.o.) decreased the period of immobility significantly. However, the locomotor activity did not show any significant change in the rota rod test and photoactometer. Discussion Thus from the above observations, it can be proposed that A. vera enhances learning and memory, and also alleviates depression in mice.

Cadmium exposure during lactation causes learning and memory-impairment in F1 generation mice: amelioration by quercetin

Abstract Cadmium (Cd) is a known pollutant present in the environment at low levels and is reported to affect reproduction in many ways. The present study was undertaken to explore the effect of Cd in F1 generation mice on cognitive parameters, and to further investigate whether quercetin could modulate these effects. In this study, female lactating mice were exposed to cadmium for seven days just after delivery. The new born pups in their adulthood were tested for learning and memory parameters by passive avoidance task and Morris water maze (MWM) test. It was observed that pups exposed to Cd showed significant impairment of memory in step down latency test, which was reversed by quercetin (100 mg/kg). In MWM test for spatial memory, animals exposed to Cd exhibited increased escape latency, which was reversed by quercetin (50 mg/kg) significantly. Quercetin alone (50 and 100 mg/kg) also demonstrated improved spatial memory, and showed improved retention memory in the passive avoidance paradigm at dose 50 mg/kg. On testing oxidative stress parameters, we observed significantly increased malondialdehyde (MDA) levels in brain tissue of Cd-treated mice. Moreover, co-treatment with quercetin (50 mg/kg) and Cd significantly reduced these MDA levels. The other doses (25 and 100 mg/kg) also showed reduction in MDA levels as compared to the group exposed to Cd alone, though the difference was not statistically significant. Hence, this study highlights the possibility of cognitive impairment in adulthood if there is Cd exposure during lactation and oxidative stress could possibly attribute to this effect.

The effect of the essential oil of Eugenia caryophyllata in animal models of depression and locomotor activity

Abstract Objective The essential oil of Eugenia caryophyllata (clove oil; Family: Myrtaceae) is used in dental care as an antiseptic and analgesic. The present study investigates the effect of clove oil on animal models of depression and locomotion. Methods Clove oil was administered in doses of 0.025, 0.05, and 0.1 ml/kg/day, intraperitoneally (i.p.) for 3 weeks. The forced swim test (FST) and the tail suspension test (TST) were used to assess depression. To evaluate locomotor activity, the rota rod test and the photoactometer procedure were performed. Results In the FST, it was observed that the duration of immobility was significantly decreased (P < 0.01) in animals treated with clove oil (0.05 and 0.1 ml/kg); however, the clove oil dose of 0.025 ml/kg showed an insignificant increase in the immobile period. The TST demonstrated that pretreatment with clove oil decreases (P < 0.01) the immobile period significantly at all the three administered doses. Similarly, the photoactometer procedure showed increased locomotor activity at all the three doses, although significant (P < 0.05) only at 0.1 ml/kg. In addition, the rota rod test showed that animals treated with clove oil (0.1 ml/kg) enhanced muscle coordination as demonstrated by a significant increase (P < 0.05) in the latency to fall from the rota rod as compared to the control. However, the lowest administered dose (0.025 ml/kg, i.p.) decreased the latency to fall from the rota rod significantly (P < 0.05) compared to the control. Clove oil (0.05 ml/kg) also showed a decrease in the latency to fall from the rota rod although the result was not statistically significant. Discussion Thus, it can be concluded that pretreatment with clove oil decreases depression and enhances locomotor activity similar to that exhibited by psychostimulants.

Cadmium Enhances Locomotor Behaviour in F1 Generation Mice Following Maternal Exposure During Lactation: Modulation by Quercetin

The present study was designed to investigate the effects of Cd exposure on locomotor behaviour in F1 mice whose dams were exposed to low dose cadmium for a short duration during the lactation period and whether quercetin could modulate the effects. The locomotor behaviour and musculoskeletal activity were tested using photoactomter and rota rod test respectively. We observed that at the given dose of Cd (1.2mg/kg) for a short duration, the muscle coordination on rota rod showed significant improvement as compared to the control group. Cotreatment of Cd with quercetin (100mg/kg) further enhanced the rota rod activity. Similarly the spontaneous motor activity as tested on the photoactometer also exhibited improvement in Cd treated group though this change was not statistically significant. However, Cd when cotreated with quercetin (50 mg/kg) showed significant enhancement in photoactometer activity compared to control. Quercetin administered alone (dose 25 mg/kg) also demonstrated significantly improved rota rod and photoactometer activity as compared to control. Thus cadmium exposure to dams at dose (1.2mg/kg) during lactation may