Pravinkumar Bhutada

Protection of cholinergic and antioxidant system contributes to the effect of berberine ameliorating memory dysfunction in rat model of streptozotocin-induced diabetes.

Memory impairment induced by streptozotocin in rats is a consequence of changes in CNS that are secondary to chronic hyperglycemia, impaired oxidative stress, cholinergic dysfunction, and changes in glucagon-like peptide (GLP). Treatment with antihyperglycemics, antioxidants, and cholinergic agonists are reported to produce beneficial effect in this model. Berberine, an isoquinoline alkaloid is reported to exhibit anti-diabetic and antioxidant effect, acetylcholinesterase (AChE) inhibitor, and increases GLP release. However, no report is available on influence of berberine on streptozotocin-induced memory impairment. Therefore, we tested its influence against cognitive dysfunction in streptozotocin-induced diabetic rats using Morris water maze paradigm. Lipid peroxidation and glutathione levels as parameters of oxidative stress and choline esterase (ChE) activity as marker of cholinergic function were assessed in the cerebral cortex and hippocampus. Thirty days after diabetes induction rats showed a severe deficit in learning and memory associated with increased lipid peroxidation, decreased reduced glutathione, and elevated ChE activity. In contrast, chronic treatment with berberine (25-100mg/kg, p.o., twice daily, 30 days) improved cognitive performance, lowered hyperglycemia, oxidative stress, and ChE activity in diabetic rats. In another set of experiment, berberine (100mg/kg) treatment during training trials also improved learning and memory, lowered hyperglycemia, oxidative stress, and ChE activity. Chronic treatment (30 days) with vitamin C or metformin, and donepezil during training trials also improved diabetes-induced memory impairment and reduced oxidative stress and/or choline esterase activity. In conclusion, the present study demonstrates treatment with berberine prevents the changes in oxidative stress and ChE activity, and consequently memory impairment in diabetic rats.

Ameliorative effect of quercetin on memory dysfunction in streptozotocin-induced diabetic rats

Diabetes-related cognitive dysfunction is a consequence of changes within the central nervous system that are secondary to chronic hyperglycemia, oxidative stress, and cholinergic dysfunction, and probably therefore anti-diabetics, anti-oxidants, and acetylcholine esterase (AChE) inhibitors were found to have beneficial effects in animal models. Quercetin, a bioflavonoid widely distributed in the plants is reported to be a potent anti-diabetic, anti-oxidant, AChE inhibitor, and memory enhancer. Therefore, we screened its influence against diabetes-induced cognitive dysfunction in streptozotocin-induced diabetic rats using Morris water and elevated plus maze (EPM) paradigms. Thirty days after diabetes induction rats exhibited marked and persistent hyperglycemia, weight loss, higher escape latency during training trials and reduced time spent in target quadrant in probe trial in Morris water maze test, and increased escape latency in EPM task. Treatment with quercetin (5-20 mg/kg, p.o., twice daily, 30 days) in streptozotocin-induced diabetic rats prevented the changes in blood glucose, body weight, and performance in Morris water and elevated plus maze tasks. In another set of experiment, quercetin (40 mg/kg, p.o., twice daily) treatment during training trials (31-35 days) markedly decreased escape latency and increased time spent in target quadrant during Morris water maze task. This treatment also decreased blood glucose levels, but had no influence on body weights. These effects were comparable to vitamin C (100 mg/kg, twice daily, 30 days) and donepezil (3 mg/kg day 31-day 35, during training trials), and devoid of any motor deficit and anxiety-like effect when tested in open field test. In conclusion, quercetin may provide a new potential option for prevention of the cognitive dysfunction in diabetes.

Anticonvulsant activity of berberine, an isoquinoline alkaloid in mice

Berberine, an isoquinoline alkaloid is reported to modulate several neurotransmitter systems like N-methyl-D-aspartate, nitric oxide and serotonin, which modulate convulsions. In addition, it is suggested that Berberis vulgaris may be useful in treatment of convulsion and epilepsy. Therefore, the present study investigated the effects of berberine in pentylenetetrazole, maximal electroshock (MES) and kainic acid (KA)-induced convulsions. The latency for development of convulsions and mortality rate was recorded in these models using mice. The results revealed that in MES-induced seizures model, berberine (10 and 20 mg/kg, i.p.) decreased duration of tonic hind limb extension and percent mortality. Moreover, these doses of berberine also protected mice against KA-induced clonic convulsions and decreased mortality. Berberine also protected mice against NMDA-induced turning behavior. Further, the anticonvulsant doses of berberine did not show any signs of motor in-coordination when tested in rotarod test. In conclusion, berberine exhibits anticonvulsant activity by modulating neurotransmitter systems and may find clinical application.

Reversal by quercetin of corticotrophin releasing factor induced anxiety- and depression-like effect in mice

Quercetin is a bioflavonoid reported to produce variety of behavioral effects like anxiolytic, antidepressant, etc. Recent gathering evidences indicated that quercetin attenuates stress-induced behavioral and biochemical effects. It also decreases CRF expression in the brain. As CRF is commonly implicated in the high-anxiety and depression, we hypothesized that quercetin may involve CRF in its anxiolytic- and antidepressant-like effects. To support such possibility, we investigated the influence of quercetin on CRF or CRF antagonist (antalarmin) induced changes in social interaction time in social interaction test, and immobility time in forced swim test. Results indicated that quercetin (20-40 mg/kg, p.o.) or antalarmin (2-4 microg/mouse, i.c.v.) dose dependently increased social interaction time and decreased immobility time indicating anxiolytic- and antidepressant-like effect. These effects were comparable with the traditional anxiolytic (diazepam, 1-2mg/kg, i.p.) and antidepressant (fluoxetine, 10-20mg/kg, i.p.) agents. Administration of CRF (0.1 and 0.3 nmol/mouse, i.c.v.) produced just opposite effects to that of quercetin on these parameters. Further, it was seen that pretreatment with quercetin (20 or 40 mg/kg, p.o.) dose dependently antagonized the effects of CRF (0.1 or 0.3 nmol/mouse, i.c.v.) in social interaction and forced swim test. The sub-effective dose of antalarmin (1 microg/mouse) when administered along with the sub-effective dose of quercetin (10mg/kg) produced significant anxiolytic-and antidepressant-like effect. These observations suggest reciprocating role of quercetin on the CRF-induced anxiogenic and depressant-like effects.

Gonadotropin-releasing hormone agonist blocks anxiogenic-like and depressant-like effect of corticotrophin-releasing hormone in mice

Corticotrophin-releasing factor (CRF) is reported to inhibit the release of gonadotropin-releasing hormone (GnRH). In addition to the endocrine effects, GnRH is reported to influence the behavior via its neuronal interactions. We therefore, hypothesized that anxiety and depression produced by CRF could be also subsequent to the decrease in GnRH. To support such possibility, we investigated the influence of GnRH agonists on CRF or CRF antagonist induced changes in social interaction time in social interaction test, and immobility time in forced swim test in mice, as the indices for anxiety and depression, respectively. Results indicated that GnRH agonists [leuprolide (20-80 ng/mouse, i.c.v.), or d-Trp-6-LHRH (40-160 ng/mouse, i.c.v.)] dose dependently increased social interaction time and decreased immobility time indicating anxiolytic- and antidepressant-like effect, respectively. Such effects of GnRH agonists were even evident in castrated mice, which suggest that these effects were unrelated to their endocrine influence. Administration of CRF (0.1 and 0.3 nmol/mouse, i.c.v.) produced just opposite effects as that of GnRH agonist on these parameters. Further, it was seen that pretreatment with leuprolide (10 or 20 ng/mouse, i.c.v.) or d-Trp-6-LHRH (20 or 40 ng/mouse, i.c.v.) dose dependently antagonized the effects of CRF (0.3 nmol/mouse, i.c.v.) in social interaction and forced swim test. CRF antagonist [alpha-Helical CRF (9-41), (1 or 10 nmol/mouse, i.c.v.)] was found to exhibit anxiolytic- and antidepressant-like effect, and its sub-effective dose (0.1 nmol/mouse, i.c.v.) when administered along with sub-threshold dose of leuprolide (10 ng/mouse, i.c.v.), or d-Trp-6-LHRH (20 ng/mouse, i.c.v.) also produced significant anxiolytic- and antidepressant-like effect. These observations suggest reciprocating role of GnRH in modulating the CRF induced anxiogenic- and depressant-like effects.

Role of nitric oxide in obsessive-compulsive behavior and its involvement in the anti-compulsive effect of paroxetine in mice

In view of the reports that nitric oxide modulates the neurotransmitters implicated in obsessive-compulsive disorder, patients with obsessive-compulsive disorder exhibit higher plasma nitrate levels, and drugs useful in obsessive-compulsive disorder influence nitric oxide, we hypothesized that nitric oxide may have some role in obsessive-compulsive behavior. We used marble-burying behavior of mice as the animal model of obsessive-compulsive disorder, and nitric oxide levels in brain homogenate were measured using amperometric nitric oxide-selective sensor method. Intraperitoneal administration of nitric oxide enhancers viz. nitric oxide precursor-l-arginine (800 mg/kg), nitric oxide donor-sodium nitroprusside (3 mg/kg) or phosphodiesterase type 5 inhibitor-sildenafil (3 mg/kg) significantly increased marble-burying behavior as well as brain nitrites levels, whereas treatment with 7-nitroindazole-neuronal nitric oxide synthase inhibitor (20-40 mg/kg, i.p.) or paroxetine-selective serotonin reuptake inhibitor (5-10 mg/kg, i.p.) dose dependently attenuated marble-burying behavior and nitrites levels in brain. Further, co-administration of sub-effective doses of 7-nitroindazole (10 mg/kg) and paroxetine (2.5 mg/kg) significantly attenuated marble-burying behavior. Moreover, pretreatment with l-arginine (400 mg/kg, i.p.), sodium nitroprusside (2.0 mg/kg, i.p.) or sildenafil (2.0 mg/kg, i.p.) significantly attenuated the inhibitory influence of 7-nitroindazole (40 mg/kg) or paroxetine (10 mg/kg) on marble-burying behavior as well as on brain nitrites levels. None of the above treatment had any significant influence on locomotor activity. In conclusion, obsessive compulsive behavior in mice appears related to nitric oxide in brain, and anti-compulsive effect of paroxetine appears to be related to decrease central levels of nitric oxide.

The 5-ht3 receptor antagonist, ondansetron, blocks the development and expression of ethanol-induced locomotor sensitization in mice

Manipulation of the serotonergic system has been shown to alter ethanol sensitization. Ondansetron is a 5-HT3 receptor antagonist, reported to attenuate cocaine and methamphetamine-induced behavioral sensitization, but no reports are available on its role in ethanol-induced behavioral sensitization. Therefore, an attempt has been made to assess this issue by using an earlier used animal model of ethanol-induced locomotor sensitization. Results indicated that ondansetron (0.25–1.0 mg/kg, subcutaneously) given before the challenge dose of ethanol (2.4 g/kg, intraperitoneally) injection, significantly and dose dependently attenuated the expression of sensitization. In addition, ondansetron (1.0 mg/kg, subcutaneously) given before ethanol injection on days 1, 4, 7, and 10 significantly blocked the development (days 1, 4, 7, and 10), and expression (day 15) of sensitization to the locomotor stimulant effect of ethanol injection. Ondansetron had no effect per se on locomotor activity and did not affect blood ethanol levels. Therefore, the results raise the possibility that ondansetron blocked the development and expression of ethanol-induced locomotor sensitization by acting on 5-HT3 receptors.

Leuprolide : A luteinizing hormone releasing hormone agonist attenuates ethanol withdrawal syndrome and ethanol-induced locomotor sensitization in mice

Ethanol inhibits the synthesis, content and release of hypothalamic luteinizing hormone releasing hormone (LHRH), and LHRH modulates the activity of several neurotransmitters that experience adaptive changes on chronic exposure to ethanol, and also implicate in ethanol dependence. Hence, it was contemplated that LHRH agonist such as leuprolide may influence the behavioral consequences of withdrawing ethanol in dependent state. In the present study, ethanol dependence was produced in mice by providing ethanol liquid diet for 10 days; and its withdrawal on day 11 led to physical signs of hyperexcitability with its peak at 6th h. Acute treatment with leuprolide (20 ng/mouse, i.c.v.), 10 min prior to peak, significantly attenuated hyperexcitability. Such effect of leuprolide was evident even in castrated mice, and castration significantly increased the hyperexcitability in ethanol withdrawal state. Chronic treatment with leuprolide (10 ng/mouse, twice daily, i.c.v.) till day 10 significantly reduced the signs of hyperexcitability in ethanol withdrawal state. In another set of experiment, ethanol (2.4 g/kg, i.p.) was administered on day 1, 4, 7, 10 and 15, which caused gradual increase in locomotor activity indicating ethanol-induced sensitization. Leuprolide (20 ng/mouse, i.c.v.), 10 min prior to the challenge dose of ethanol (2.4 g/kg, i.p.) on day 15 significantly attenuated the expression of sensitization to hyperlocomotor effect of ethanol. Similarly, administration of leuprolide (20 ng/mouse, i.c.v.), 10 min prior to ethanol on day 1, 4, 7 and 10 not only reduced the gradual increase in locomotor activity but also attenuated the sensitized locomotor response on day 15, indicated attenuation of development of sensitization. Leuprolide per se did not affect physical signs and locomotor activity in control group. In conclusion, the present study demonstrated that leuprolide treatment attenuates expression and development of ethanol dependence and sensitization in mice.

Increased marble-burying behavior in ethanol-withdrawal state: Modulation by gonadotropin-releasing hormone agonist

A characteristic behavior in alcohol abstinence state indicates the possibility of obsessive-compulsive behavior in alcoholics. Ethanol is known to reduce hypothalamic synthesis, release, and mRNA expression of gonadotropin-releasing hormone (GnRH) that modulates serotonergic, dopaminergic, and glutamatergic systems, which experience adaptive changes on chronic exposure to ethanol. Such changes are also evident in obsessive-compulsive disorder. Therefore, it was proposed to investigate the effect of ethanol-withdrawal on marble-burying behavior in mice, particularly because it simulates some aspects of obsessive-compulsive behavior; further, the influence of GnRH agonist was studied on the same. Ethanol-withdrawal state was induced after its chronic administration, and marble-burying behavior was observed at 0, 6, 24, 48, and 96 h interval. Further, the influence of leuprolide--a GnRH agonist (50-600 microg/kg, s.c.) or fluoxetine (5-30 mg/kg, i.p.) was investigated on ethanol-withdrawal-induced changes in marble-burying behavior. The results indicated that ethanol-withdrawal led to a gradual increase in marble-burying behavior upto 48 h with peak at 24 h interval. Administration of leuprolide (100-600 microg/kg, s.c.), 30 min prior to 24 h interval, dose dependently reduced ethanol-withdrawal-induced increase in marble-burying behavior, and this effect was comparable to that of fluoxetine (15 and 30 mg/kg, i.p.). Further, twice daily administration of leuprolide (50 microg/kg, s.c), concomitant with ethanol, prevented the gradual increase in marble-burying behavior after ethanol-withdrawal and this effect was comparable to fluoxetine (5 mg/kg, i.p.). In conclusion, ethanol-withdrawal on chronic administration increases marble-burying behavior in mice; its development and expression is attenuated by leuprolide.

Inhibitory influence of mecamylamine on the development and the expression of ethanol-induced locomotor sensitization in mice

Several evidences have indicated the involvement of neuronal nicotinic acetylcholine receptors (nAChR) in behavioral effects of drugs of abuse, including ethanol. nAChRs are implicated in ethanol-induced behaviors as well as neurochemical responses to ethanol. Recently, it is demonstrated that mecamylamine, a nAChR antagonist blocks cocaine-, d-amphetamine-, ephedrine-, nicotine-, and methylphenidate-induced psychomotor sensitization. However, no reports are available on its role in ethanol-induced psychomotor sensitization. Therefore, an attempt was made to evaluate its effect on ethanol-induced locomotor sensitization using a model previously described by us. The results revealed that acute administration of mecamylamine (1 and 2mg/kg, i.p.) blocked the acute stimulant effect of ethanol (2.0g/kg, i.p.). In addition, treatment with mecamylamine (0.5-2.0mg/kg, i.p.), 30min prior to the challenge dose of ethanol (2.0g/kg, i.p.) dose dependently attenuated expression of sensitization to locomotor stimulant effect of ethanol. Moreover, administration of mecamylamine (1 and 2mg/kg, i.p.) during development (prior to each ethanol injection on days 1, 4, 7, and 10) blocked acquisition as well as expression (day 15) of sensitization to locomotor stimulant effect of ethanol. Mecamylamine per se did not affect locomotor activity. Further, it also did not influence blood ethanol levels and rotarod performance in mice. These results support the hypothesis that neuroadaptive changes in nAChRs may participate in the development and the expression of ethanol-induced locomotor sensitization.