Alteration in cognitive behaviour, brain antioxidant enzyme activity and their gene expression in F1 generation mice, following Cd exposure during the late gestation period: modulation by quercetin.

We investigated whether in-utero Cd(II) chloride exposure of the dams between 14th to 21st day of gestation affects memory and learning, oxidative stress, antioxidant enzyme activity and their gene expression in brain of the pups in their adulthood. In the Morris water maze, cadmium (Cd) exposure impaired spatial memory which was reversed following co-treatment with quercetin (100 mg/kg). In the passive avoidance paradigm, retention memory was adversely affected but was significantly reversed by co treatment with quercetin (25, 50, 100 mg/kg). The malondialdehyde and catalase (CAT) levels and glutathione-S-transferase (GST) activity were increased significantly in Cd-treated group, but were reversed by quercetin (all doses). The gene expression for CAT and GST in brain tissue of Cd treated animals also increased many folds as compared to the control, and this effect was decreased on co-treatment with quercetin (all doses), thus matching with the respective enzyme activities. Quercetin (25 mg/kg) when co-treated with Cd caused a decrease in GST activity compared to control, which points towards a complex interplay with oxidative free radicals and promoters and transcription factors. Thus, Cd exposure during late gestation causes impaired spatial and retention memory in the next generation which may be due to alteration of activity as well as gene expression of the antioxidant enzymes, CAT and GST. Quercetin may offer some protection of memory impairment probably by modulating these effects.

Drug combinations in diabetic neuropathic pain: an experimental validation.

BACKGROUND: Diabetic neuropathy is the most common complication of diabetes mellitus, and the different drug combinations available do not provide effective pain relief. The present study was performed to observe the effect of amitripyline, duloxetine, sitagliptin, and pregabalin, and their combinations on streptozotocin (STZ)-induced diabetic neuropathy. METHODS: Diabetic neuropathy was induced by STZ, and the tail-flick test was used to assess thermal hyperalgesia before and after (at 30, 60, and 120 min) drug administration. One week after STZ administration, the blood glucose level was observed to be in the diabetic range. RESULTS: Administration of all the drugs except sitagliptin increased the tail-flick latency significantly as compared to control. Further, the drugs amitriptyline, duloxetine, and pregabalin showed significant pain-relieving effect, when either two of them were administered in combination, although the different combinations had varied degree of pain relief. However, sitagliptin was observed to have no effect when administered alone or in combination with the other three drugs. CONCLUSIONS: Therefore, the study provides new insights concerning combined therapy of pain, which further needs clinical exploration.

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

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.

Quercetin Modulates the Effects of Chromium Exposure on Learning, Memory and Antioxidant Enzyme Activity in F1 Generation Mice.

In the present study, we investigated whether chromium (Cr) administered to the dams (F0) during lactation period could affect memory and oxidative stress in F1 generation mice in their adulthood and whether quercetin could modulate these effects. Morris water maze (MWM) was used to test for spatial memory. Passive avoidance task and elevated plus maze were used to test for acquisition and retention memory. Oxidative stress was evaluated by measuring glutathione-S-transferase (GST), catalase activity and malonaldehyde (MDA) levels in the brain tissue. The results of MWM showed that the animals in the Cr-treated group compared to control have better spatial memory that was further enhanced when Cr was administered along with quercetin (50 mg/kg). The elevated plus maze test also showed the Cr-treated group to improve acquisition as well as retention memory compared to control. Co-treatment with quercetin (all doses) also exhibited enhanced acquisition and retention memory compared to control. The passive avoidance task demonstrated no significant improvement in memory in the Cr-treated mice but co-treatment with quercetin (100 mg/kg) showed improved acquisition memory compared to control which was significantly better than the animals treated with chromium alone. GST activity was significantly increased in the Cr-treated animals, and this was further increased in groups treated with Cr and quercetin (all doses). Chromium when administered alone and in combination with quercetin (all doses) significantly reduced MDA levels. However, Cr treatment did not show significant change in catalase activity. Nevertheless, co-treatment with quercetin (25 and 50 mg/kg) resulted in significant decrease in catalase activity. Thus, our study demonstrates that Cr exposure during lactation could be beneficial for pups with respect to augmentation of cognitive function and reduction of oxidative stress. Quercetin could probably enhance this effect to some extent.

Commiphora mukul attenuates peripheral neuropathic pain induced by chronic constriction injury of sciatic nerve in rats.

OBJECTIVE: The management of neuropathic pain remains unsatisfactory till date, despite immense advances in the therapeutic strategies. Commiphora mukul (CM), also known as Commiphora wightii, is well known in the traditional Indian system of medicine, and has been used to treat ailments such as obesity, bone fractures, arthritis, inflammation, cardiovascular diseases, and lipid disorders. The present study was performed to investigate the effect of CM on peripheral neuropathic pain in rats. METHODS: Neuropathic pain was induced by the chronic constriction injury of the sciatic nerve. Following this, CM was orally administered for 2 weeks in doses of 50, 100, and 200 mg/kg, and pain assessment was performed by employing the behavioral tests for thermal hyperalgesia (hot-plate and tail-flick tests) and cold allodynia (acetone test). RESULTS: Following the induction of neuropathic pain, significant development of thermal hyperalgesia and cold allodynia was observed. The administration of CM (50 mg/kg) did not have any effect on the hot-plate and tail-flick tests, but significant anti-allodynic effect was observed in the acetone test. Furthermore, administration of CM (100 mg/kg) caused significant decrease in pain as observed on the tail-flick and acetone tests, but not in the hot-plate test. CM in a dose of 200 mg/kg significantly modulated neuropathic pain as observed from the increased hot-plate and tail-flick latencies, and decreased paw withdrawal duration (in acetone test). DISCUSSION: Therefore, the present study suggests that CM may be used in future as a treatment option for neuropathic pain.

Analgesic effect of piracetam on peripheral neuropathic pain induced by chronic constriction injury of sciatic nerve in rats.

Despite immense advances in the treatment strategies, management of neuropathic pain remains unsatisfactory. Piracetam is a prototype of nootropic drugs, used to improve cognitive impairment. The present study was designed to investigate the effect of piracetam on peripheral neuropathic pain in rats. Neuropathic pain was induced by the chronic constriction injury of the sciatic nerve. Following this, piracetam was intraperitoneally administered for 2 weeks in doses of 50, 100 and 200 mg/kg, and pain was assessed by employing the behavioural tests for thermal hyperalgesia (hot plate and tail flick tests) and cold allodynia (acetone test). After the induction of neuropathic pain, significant development of thermal hyperalgesia and cold allodynia was observed. The administration of piracetam (50 mg/kg) did not have any significant effect on all the behavioural tests. Further, piracetam (100 mg/kg) also had no effect on the hot plate and tail flick tests; however it significantly decreased the paw withdrawal duration in the acetone test. Piracetam in a dose of 200 mg/kg significantly modulated neuropathic pain as observed from the increased hot plate and tail flick latencies, and decreased paw withdrawal duration (in acetone test). Therefore, the present study suggests the potential use of piracetam in the treatment of neuropathic pain, which merits further clinical investigation.

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.

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

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.

Aloe vera improves memory and reduces depression in mice.

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.

Melatonin attenuates cognitive dysfunction and reduces neural oxidative stress induced by phosphamidon.

Melatonin is an important modulator of nervous system functioning and important neural antioxidant. Organophosphate pesticides like phosphamidon (PHOS) have 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 PHOS on 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 the levels of malondialdehyde (MDA) and nonprotein thiols (NP-SH) in isolated homogenized whole brain samples. The results showed a significant reduction in SDL and prolongation of TL in the PHOS (1.74 mg/kg/day; p.o.)-treated group at weeks 6 and 8 as compared to the control group. Two-week treatment with MEL (5 mg/kg/day; i.p.) antagonized the effect of PHOS on SDL as well as TL. PHOS alone produced a significant increase in the brain MDA levels and decrease in the brain NP-SH levels. Treatment with MEL attenuated the effect of PHOS on oxidative stress. Together the results showed that MEL attenuated the cognitive dysfunction and decreased oxidative stress induced by PHOS in the brain.

Effect of piracetam and vitamin E on phosphamidon-induced impairment of memory and oxidative stress in rats.

Organophosphate pesticides, such as phosphamidon (PHOS), have been shown to adversely affect memory and induce oxidative stress after both acute and chronic exposure. The present study was therefore designed to investigate the effects of piracetam (PIR) and vitamin E on PHOS-induced modulation of cognitive function and oxidative stress in rats. 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 the levels of malondialdehyde (MDA) and nonprotein thiols (NP-SH) in isolated homogenized whole brain samples. The results showed a significant reduction in SDL and a prolongation of TL in the PHOS (1.74 mg/kg/day per oral; p.o.)-treated group at weeks 6 and 8, as compared to the control group. Administration of PIR (600 mg/kg/day p.o.) or vitamin E (125 mg/kg/day p.o.) for 2 weeks antagonized the effect of PHOS on SDL as well as TL. PHOS per se produced a significant increase in brain MDA levels and a decrease in brain NP-SH levels, whereas administration of PIR (600 mg/kg/day p.o.) or vitamin E (125 mg/kg/day p.o.) attenuated these effects. Thus, the results of the study showed that both PIR and vitamin E attenuated the cognitive dysfunction and oxidative stress induced by PHOS in the rat brain.

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

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.

Acute effect of Aloe vera gel extract on experimental models of pain.

The present study was performed to explore the effect of aqueous extract of Aloe vera on behavioural parameters of pain. Pain assessment was performed by the tail-flick and formalin tests. A. vera (100 mg/kg, per oral (p.o.)) produced an insignificant decrease in the pain response in the tail-flick and formalin tests. Moreover, A. vera (200 and 400 mg/kg, p.o.) did not have significant effect on the tail-flick test. However, A. vera (200 and 400 mg/kg, p.o.) significantly decreased the second phase of the formalin-induced pain. Thus, these findings suggest that A. vera exerts its effect by a peripheral mechanism of action rather than central.

Augmented humoral immune response and decreased cell-mediated immunity by Aloe vera in rats.

OBJECTIVE: The present study was performed to explore the effect of aqueous extract of Aloe vera on parameters of humoral and cell-mediated immunity. MATERIALS AND METHODS: Delayed-type hypersensitivity was assessed by measuring foot pad thickness following sensitisation by keyhole limpet haemocyanin injection and subsequently challenged by the same. Humoral immunity was assessed by measurement of haemagglutination titre to sheep red blood cells. RESULTS: Aloe vera (400 mg/kg, p.o.) produced a significant decrease in foot pad thickness compared with the control group, and also significantly enhanced the secondary humoral immune response. CONCLUSION: Thus, these findings suggest that A. vera can modulate immune response by augmenting secondary humoral immunity and decreasing cell-mediated immunity.

Acute effect of essential oil of Eugenia caryophyllata on cognition and pain in mice.

The essential oil of Eugenia caryophyllata (clove oil; Family: Myrtaceae) is used in dental care as an antiseptic and analgesic. The study aims to evaluate the effect of clove oil on experimental models of pain and cognition in mice. To observe the acute effects of clove oil at different doses, the elevated plus maze was used for the assessment of cognition, and the tail flick and formalin tests were used for the study of pain. The formalin test showed that clove oil (0.1 ml/kg, i.p.) demonstrated significantly reduced pain response in both the phases. The lower doses (0.025 and 0.05 ml/kg, i.p.) reduced the formalin-induced pain response significantly in the second phase only. The tail-flick test showed variable response. The dose 0.1 ml/kg, clove oil, significantly decreased the tail-flick latency at 30 min and this effect was reversed by naloxone (1 mg/kg). On the contrary, the dose 0.025 ml/kg of clove oil, at 30 and 60 min increased the mean tail-flick latency compared to control group, but this effect was not statistically significant. Yet naloxone significantly (p < 0.05) reversed the effect of clove oil 0.025 ml/kg at 30 min. Clove oil (0.025 and 0.05 ml/kg, i.p.) significantly reversed the scopolamine-induced retention memory deficit induced by scopolamine, but clove oil (0.1 ml/kg, i.p.) significantly reversed both acquisition as well as retention deficits in elevated plus maze induced by the scopolamine. Clove oil exhibits reduced pain response by a predominantly peripheral action as evidenced by formalin test and the tail flick test showed the involvement of opioid receptors. Clove oil also significantly improved scopolamine-induced retention memory deficit at all doses.

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.

Effect of progesterone on phosphamidon-induced impairment of memory and oxidative stress in rats.

Progesterone (a neurosteroid) is an important modulator of the nervous system functioning. Organophosphorus pesticides like phosphamidon have been shown to adversely affect memory and induce oxidative stress on both acute and chronic exposure. The present study was therefore designed to investigate the effects of progesterone (PROG) on phosphamidon-induced modulation of cognitive function and oxidative stress in rats. 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 the levels of thiobarbituric acid reactive species (TBARS) and non-protein thiols (NP-SH) in isolated homogenized whole brain samples. The results showed a significant reduction in SDL and prolongation of TL in the phosphamidon (1.74 mg/kg/d; p.o.) treated group at weeks 6 and 8 as compared to the control group. Two weeks treatment with PROG (15 mg/kg/d; i.p.) antagonized the effect of phosphamidon on SDL as well as TL. Phosphamidon alone produced a significant increase in the brain TBARS levels and decrease in the brain NP-SH levels. Treatment with PROG (15 mg/kg/d; i.p.) attenuated the effect of phosphamidon on oxidative stress. Together, the results showed that progesterone attenuated the cognitive dysfunction and increased oxidative stress induced by phosphamidon in the brain.

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.

Peripheral interaction of opioid and NMDA receptors in inflammatory pain in rats.

Both opioid and NMDA receptors have been known to be involved in pain processing in the central nervous system as well as in the periphery. The effect of drugs acting on opioid and NMDA receptors, and their role in modulation of pain response was observed in the formalin model of inflammatory pain in rats. We have demonstrated that morphine has significant antinociceptive effect in the formalin model and this effect was enhanced when given in combination with ketamine. We have also reported modulation of pain response when naloxone or NMDA were co-administered with morphine or ketamine in various combinations. A noteworthy observation in our study is that low dose naloxone when co-administered with ketamine and morphine, or with ketamine and NMDA, caused decrease in the pain response. These observations may suggest that low dose naloxone can cause modulation of opioid and NMDA receptors resulting in antinociceptive effect. Our study thus introduces a new concept of more than two drugs acting on opioid and NMDA receptors to modulate pain response.

Comparative effect of Ocimum sanctum, Commiphora mukul, folic acid and ramipril on lipid peroxidation in experimentally-induced hyperlipidemia.

Treatment with C. mukul and O. sanctum, showed a significant decrease in cholesterol and triglyceride levels respectively. O. sanctum also significantly increased serum HDL-cholesterol compared to control. Serum MDA levels were significantly reduced in all the treated groups compared to control suggesting that each of the drugs under study were effective in their free radical scavenging action. Erythrocyte SOD activity was increased in all the treatment groups with C. mukul showing the maximum effect followed by O. sanctum, folic acid and ramipril. The erythrocyte CAT activity was significantly increased in all the drug treated groups with maximum increase seen in O. sanctum and ramipril treated groups, whereas lesser effects were observed with C. mukul and folic acid groups. Thus, the indigenous drugs, C. mukul and O. sanctum had beneficial effect on hypercholesterolemic rabbit model, both in terms of lipid profile as well as antioxidant potential. Ocimum sanctum was found to be the most promising of all the drugs. Moreover, it could be hypothesized that these plant products along with folic acid and ramipril can be explored for synergistic effect for treatment for hypercholesterolemic conditions.