Defensive effect of natrium diethyldithiocarbamate trihydrate (NDDCT) and lisinopril in DOCA-salt hypertension-induced vascular dementia in rats

Roflumilast attenuates cognitive deficits in estrogen insufficient rats

Estrogen replacement therapy including specific estrogen receptor alpha (ERα) agonist, 4,4',4″-(4-propyl-[1H] pyrazole-1,3,5-triyl) trisphenol (PPT), improves cognitive function in the females with estrogen insufficiency condition. It is well suggested that the cyclic nucleotides are considered as one of the downstream mediators to ERα receptor activity and they can be hypothesized as a potential target in the management of estrogen insufficiency condition. Roflumilast, a phosphodiesterase-4 inhibitor, increases the level of cyclic adenosine monophosphate (cAMP) in most of the tissues including the brain, and is reported to have procognitive activity in the experimental animals. Hence, the present study evaluated the therapeutic effect of roflumilast with or without PPT in rats with experimentally-induced estrogen insufficiency. Estrogen insufficiency was induced in female rats through bilateral ovariectomy on day-1 (D-1) of the experimental schedule. Roflumilast (0.3 and 1.0 mg/kg; p.o.) and PPT (333µg/kg; i.p.) attenuated ovariectomy-induced cognitive deficits in the rodents during behavioral tests. Roflumilast and PPT increased the cholinergic function and cAMP level in the rat hippocampus and prefrontal cortex. Further, ovariectomy-induced decrease in the extent of phosphorylation of ERα in both the brain regions was attenuated with the monotherapy of either roflumilast or PPT. Interestingly, the combination of 1.0 mg/kg roflumilast and PPT exhibited better therapeutic effectiveness than their monotherapy. In addition, roflumilast facilitated PPT-induced increase in the level of expression of phosphorylated protein kinase-B (Akt) in both the rat brain regions. Hence, it can be assumed that the combination of roflumilast and PPT could be a therapeutic option in the management of estrogen insufficiency-induced disorders.

Ginkgolide B Alleviates Learning and Memory Impairment in Rats With Vascular Dementia by Reducing Neuroinflammation via Regulating NF-κB Pathway

Ginkgobalide B (GB) as the main active ingredient of traditional Chinese medicine Ginkgo biloba extract is reported to reduce neuroinflammation, protect neurons and promote cognitive learning ability. To explore that GB can reduce neuroinflammation through regulating nuclear factor-kappaB (NF-κB) signaling pathway and overcome cognitive dysfunction in rats with vascular dementia (VD), we aim at investigating the potential effect of GB on enhancing cognitive function in rats with VD. It was found that GB improved survival of oxygen-glucose deprivation (OGD) treated SH-SY5Y cells by attenuating inflammatory response via Toll-like Receptor 4 (TLR4)/NF-κB pathway. When rats were treated with bilateral common carotid artery occlusion (BCCAO) for 24 h, saline and GB were administered in Sprague-Dawley (SD) rats via a single intraperitoneal injection for consecutive 14 days. The behavioral changes of VD like rats treated with GB were observed through open field test, Morris water maze (MWM) and Y-maze electric maze. Nissl staining and immunofluorescence were used to observe changes of neurons in the hippocampus of rats. Western blot analysis was performed by detecting NF-κB pathway related inflammatory factors. The results found that GB can significantly improve the learning and memory ability of VD rats by reducing TLR4/NF-κB mediated neuroinflammation. In conclusion, GB seemed to be a potential drug for amelioration of learning and memory impairment in rats with VD.

Sodium hydrogen sulfide upregulates cystathionine β-synthase and protects striatum against 3-nitropropionic acid-induced neurotoxicity in rats

OBJECTIVES

Hydrogen sulfide (H2S) is a neuromodulator that plays a protective role in multiple neurodegenerative diseases including Alzheimer's (AD) and Parkinson's (PD). However, the precise mechanisms underlying its effects against Huntington's disease (HD) are still questioned.This study aimed to examine the neuroprotective effects of sodium hydrogen sulfide (NaHS; H2S donor) against 3-nitropropionic acid (3NP)-induced HD like pathology in rats. Methods: Male Wistar rats were randomly allocated into four groups; (1) normal control receiving saline; (2) NaHS control receiving (0.5 mg/kg/day, i.p.) for 14 days; (3,4) receiving 3NP (10 mg/kg/day, i.p.) for 14 days, with NaHS 30 min later in group 4.

KEY FINDINGS

NaHS improved cognitive and locomotor deficits induced by 3NP as confirmed by the striatal histopathological findings. These former events were biochemically supported by the increment in cystathionine β-synthase (CBS) gene expression, reduction of glutamate (Glu), dopamine (DA), malondialdehyde (MDA), tumour necrosis factor-alpha (TNF-α), cytochrome-c, cleaved caspase-3 and pc-FOS indicating antioxidant, anti-inflammatory as well as anti-apoptotic effects. Furthermore, NaHS pretreatment improved cholinergic dysfunction and increased brain-derived neurotropic factor (BDNF) and nuclear factor erythroid-2-related factor 2 (Nrf2).

CONCLUSIONS

These findings suggest that appropriate protection with H2S donors might represent a novel approach to slow down HD-like symptoms.

Endothelium-Independent Vasodilatory Effect of Sailuotong (SLT) on Rat Isolated Tail Artery

Background

Sailuotong (SLT) is a standardized three-herb formulation consisting of extracts of Panax ginseng, Ginkgo biloba, and Crocus sativus for the treatment of vascular dementia (VaD). Although SLT has been shown to increase cerebral blood flow, the direct effects of SLT on vascular reactivity have not been explored. This study aims to examine the vasodilatory effects of SLT and the underlying mechanisms in rat isolated tail artery.

Methods

Male (250-300 g) Wistar Kyoto (WKY) rat tail artery was isolated for isometric tension measurement. The effects of SLT on the influx of calcium through the cell membrane calcium channels were determined in Ca²⁺-free solution experiments.

Results

SLT (0.1-5,000 μg/ml) caused a concentration-dependent relaxation in rat isolated tail artery precontracted by phenylephrine. In the contraction experiments, SLT (500, 1,000, and 5,000 μg/mL) significantly inhibited phenylephrine (0.001 to 10 μM)- and KCl (10-80 mM)-induced contraction, in a concentration-dependent manner. In Ca²⁺-free solution, SLT (500, 1,000, and 5,000 μg/mL) markedly suppressed Ca²⁺-induced (0.001-3 mM) vasoconstriction in a concentration-dependent manner in both phenylephrine (10 μM) or KCl (80 mM) stimulated tail arteries. L-type calcium channel blocker nifedipine (10 μM) inhibited PE-induced contraction. Furthermore, SLT significantly reduced phenylephrine-induced transient vasoconstriction in the rat isolated tail artery.

Conclusion

SLT induces relaxation of rat isolated tail artery through endothelium-independent mechanisms. The SLT-induced vasodilatation appeared to be jointly meditated by blockages of extracellular Ca²⁺ influx via receptor-gated and voltage-gated Ca²⁺ channels and inhibition of the release of Ca²⁺ from the sarcoplasmic reticulum.

Vinpocetine facilitates the anti-amnesic activity of estrogen-receptor alpha agonist in bilateral ovariectomy-challenged animals

The fluctuation in plasma estrogen level influences the cognitive function in the females. The specific estrogen receptor alpha (ERα) agonist, (4,4',4″-(4-propyl-[1 H] pyrazole-1,3,5-triyl) tris phenol (PPT), is reported to exhibit therapeutic activity similar to that of estrogen replacement therapy. However, the former can also exert cyclic adenosine monophosphate (cAMP)-dependent carcinogenic activity in the uterus of the ovariectomized animals. Moreover, there is no report of cGMP on ERα-mediated phosphorylation of Akt in the experimental condition. Vinpocetine increases the rate of formation of cGMP than cAMP in several tissues. Hence, the present study evaluated the neuroprotective effect of vinpocetine with or without PPT against ovariectomy-induced dementia in experimental rodents. The condition of estrogen insufficiency was induced in female rats through bilateral ovariectomy on day-1 (D-1) of the experimental schedule. Vinpocetine (20 mg/kg) and PPT attenuated ovariectomy-induced cognitive deficits in behavioral tests and increase in body weight in the rodents. Vinpocetine and PPT increased the cholinergic function and the ratio of cGMP/cAMP in the hippocampus, pre-frontal cortex and amygdala of the ovariectomized animals. Further, ovariectomy-induced decrease in the extent of phosphorylation of ERα in all brain regions was attenuated with the monotherapy of either vinpocetine or PPT. Interestingly, the combination of vinpocetine and PPT exhibited better effectiveness than their monotherapy. However, vinpocetine attenuated the PPT-induced increased level of phosphorylated Akt in discrete brain regions and weight of uterus of these rodents. Hence, the combination could be considered as a better alternative candidate with minimal side effects in the management of estrogen insufficiency-induced disorders.

Sildenafil promotes the anti-amnesic activity of estrogen receptor alpha agonist in animals with estrogen insufficiency

The cognitive function in the females is observed to modulate with the fluctuation in plasma estrogen level. The specific estrogen receptor alpha (ERα) agonist, (4,4',4″-(4-propyl-[1H] pyrazole-1,3,5-triyl) tris phenol (PPT), exerts similar therapeutic activity to that of estrogen replacement therapy. It can also exert cyclic adenosine monophosphate (cAMP)-dependent carcinogenic activity in the uterus of the ovariectomized animals. However, there is no report of cGMP on the ERα-mediated phosphorylation of Akt in the experimental condition. Sildenafil increases the level of cGMP in most of the tissues including brain. Hence, the present study evaluated the therapeutic effect of Sildenafil with or without PPT in rats with experimentally-induced estrogen insufficiency. The condition of estrogen insufficiency was induced in female rats through bilateral ovariectomy on day-1 (D-1) of the experimental schedule. Sildenafil (1.0 and 10.0 mg/kg) and PPT attenuated ovariectomy-induced cognitive deficits in behavioural tests and increase in body weight in the rodents. Sildenafil and PPT increased the cholinergic function and the ratio of cGMP/cAMP in the hippocampus, pre-frontal cortex and amygdala of the animals. Further, the ovariectomy-induced decrease in the extent of phosphorylation of ERα in all the brain regions was attenuated with the monotherapy of either Sildenafil or PPT. Interestingly, the combination of Sildenafil and PPT exhibited better therapeutic effectiveness than their monotherapy. However, Sildenafil attenuated the PPT-induced increase in the level of expression of phosphorylated protein kinase-B (Akt) in the discrete brain regions and the weight of uterus of these rodents. Hence, it can be assumed that the combination could be a better therapeutic alternative with minimal side effect in the management of estrogen insufficiency-induced disorders.

Prevention of hypertension-induced vascular dementia by Lactobacillus paracasei subsp. paracasei NTU 101-fermented products

CONTEXT

Numerous etiological studies have established positive clinical association between hypertension and vascular dementia (VaD). Lactobacillus paracasei subsp. paracasei NTU 101-fermented products have been shown to decrease vascular risk factors such as hypertension, atherosclerosis, hyperlipidemia and obesity.

OBJECTIVE

This study investigated the effect of ethanol extract of Lactobacillus paracasei subsp. paracasei NTU 101-fermented products (NTU101F) in hypertension-induced VaD in rats.

MATERIALS AND METHODS

Hypertension was promoted by subcutaneous injection of deoxycorticosterone acetate (DOCA, 25 mg/kg body weight/day, twice a week) and substitution of drinking water with 1.0% NaCl and 0.2% KCl. The NTU101F groups (0.5, 1.0, and 5.0) administered NTU101F at the concentrations 11, 22, and 110 mg/kg body weight/day, respectively, starting from day 51 day of DOCA-salt treatment. Morris water maze (MWM) was used for testing learning and memory. Different biochemical estimations were used to assess oxidative stress and inflammatory response in hippocampus.

RESULTS

Oral administration of NTU101F in DOCA-salt hypertension-induced VaD rats resulted in a significant decrease in blood pressure by 18.3-23.2% (p < 0.001), which was regulated by increasing eNOS density (about 3-fold) in the aorta, promoting NO production, and decreasing of matrix metallopeptidase 9 activity (about 2-fold) in the hippocampus, in addition to improve the kidney function and structure, decrease escape latency and increase the times spent in the target quadrant by 23.5-27.8% (p < 0.05).

CONCLUSION

Overall, our findings suggest that NTU101F could exert neuroprotection in the brain and attenuate hypertension-induced VaD.

Angiotensin II, hypertension and angiotensin II receptor antagonism: Roles in the behavioural and brain pathology of a mouse model of Alzheimer's disease

Elevated angiotensin II causes hypertension and contributes to Alzheimer's disease by affecting cerebral blood flow. Angiotensin II receptor blockers may provide candidates to reduce (vascular) risk factors for Alzheimer's disease. We studied effects of two months of angiotensin II-induced hypertension on systolic blood pressure, and treatment with the angiotensin II receptor blockers, eprosartan mesylate, after one month of induced hypertension in wild-type C57bl/6j and AβPPswe/PS1ΔE9 (AβPP/PS1/Alzheimer's disease) mice. AβPP/PS1 showed higher systolic blood pressure than wild-type. Subsequent eprosartan mesylate treatment restored this elevated systolic blood pressure in all mice. Functional connectivity was decreased in angiotensin II-infused Alzheimer's disease and wild-type mice, and only 12 months of Alzheimer's disease mice showed impaired cerebral blood flow. Only angiotensin II-infused Alzheimer's disease mice exhibited decreased spatial learning in the Morris water maze. Altogether, angiotensin II-induced hypertension not only exacerbated Alzheimer's disease-like pathological changes such as impairment of cerebral blood flow, functional connectivity, and cognition only in Alzheimer's disease model mice, but it also induced decreased functional connectivity in wild-type mice. However, we could not detect hypertension-induced overexpression of Aβ nor increased neuroinflammation. Our findings suggest a link between midlife hypertension, decreased cerebral hemodynamics and connectivity in an Alzheimer's disease mouse model. Eprosartan mesylate treatment restored and beneficially affected cerebral blood flow and connectivity. This model could be used to investigate prevention/treatment strategies in early Alzheimer's disease.

Neuroprotective Effects of Nicorandil in Chronic Cerebral Hypoperfusion-Induced Vascular Dementia

BACKGROUND

Ischemia-induced chronic cerebral hypoperfusion (CCH) is associated with reduced cerebral blood flow and vascular dementia (VaD). Brain mitochondrial potassium (adenosine triphosphate-sensitive potassium [K_ATP]) channels have a beneficial role in various brain conditions. The utility of K_ATP channels in CCH-induced VaD is still unknown. The aim of this study is to investigate the role of nicorandil, a selective K_ATP channel opener, in CCH-induced VaD.

METHODS

The method of 2-vessel occlusion (2VO) was used to induce CCH in mice. Cognitive impairment was assessed using Morris water maze. Serum nitrosative stress (nitrite/nitrate), brain cholinergic dysfunction (acetylcholinesterase [AChE] activity), brain oxidative stress (thiobarbituric acid reactive substances, glutathione [GSH], catalase [CAT], and superoxide dismutase [SOD]), inflammation (myeloperoxidase [MPO]), and infarct size (2,3,5-triphenyltetrazolium chloride staining) were assessed.

RESULTS

2-vessels-occluded animals have shown significant cognitive impairment, serum nitrosative stress (reduced nitrite/nitrate), cholinergic dysfunction (increased brain AChE activity), and increased brain oxidative stress (reduction in GSH content and SOD and CAT activities with a significant increase in lipid peroxidation), along with a significant increase in MPO activity and infarct size. However, nicorandil treatment has significantly attenuated various CCH-induced behavioral and biochemical impairments.

CONCLUSIONS

It may be said that 2VO provoked CCH leading to VaD, which was attenuated by the treatment of nicorandil. So, modulation of K_ATP channels may provide benefits in CCH-induced VaD.

Effects of equol on deoxycorticosterone acetate salt-induced hypertension and associated vascular dementia in rats

Oxidative stress is the major cause of neuronal cell degeneration observed in neurodegenerative diseases including vascular dementia (VaD), and hypertension has been found to increase the probability of VaD. Here, we investigated the effects of equol in deoxycorticosterone acetate (DOCA)-salt-induced hypertensive rats (DHRs) and the associated VaD. The systolic blood pressure of rats treated with low- (10 mg per kg body weight) and high-dose (20 mg per kg body weight) equol for 4 weeks was lower than that of the control group by 12.18 and 17.48% in a dose-dependent manner, respectively (p < 0.05), which was regulated by inhibiting angiotensin-converting enzyme (ACE) activity and increasing the nitric oxide (NO) production. Equol-treated DHRs showed a significant decrease in both the swimming distance and time required to reach the escape platform (78.20 to 82.56%, p < 0.05). In addition, the probe trial session and working memory test indicated that equol improved the long- and short-term memory of the rats. Moreover, the brain antioxidant activity was increased by elevating the activities of superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPx) levels, and the malondialdehyde (MDA) content and acetylcholinesterase (AChE) activity were decreased, indicating that equol suppressed oxidative stress. In conclusion, we demonstrated that equol exhibited comparable blood pressure (BP)-lowering and VaD-improving effects with the clinically used drug, lisinopril in DHRs while there was a positive correlation between the doses. Therefore, this bioactive compound may be useful for developing functional foods, thereby extending the application of equol-containing crops.

Effect of ruthenium red, a ryanodine receptor antagonist in experimental diabetes induced vascular endothelial dysfunction and associated dementia in rats

Diabetes mellitus is considered as a main risk factor for vascular dementia. In the past, we have reported the induction of vascular dementia by experimental diabetes. This study investigates the efficacy of a ruthenium red, a ryanodine receptor antagonist and pioglitazone in the pharmacological interdiction of pancreatectomy diabetes (PaD) induced vascular endothelial dysfunction and subsequent vascular dementia in rats. Attentional set shifting and Morris water-maze test were used for assessment of learning and memory. Vascular endothelial function, blood brain barrier permeability, serum glucose, serum nitrite/nitrate, oxidative stress (viz. aortic superoxide anion, brain thiobarbituric acid reactive species and brain glutathione), brain calcium and inflammation (myeloperoxidase) were also estimated. PaD rats have shown impairment of endothelial function, blood brain barrier permeability, learning and memory along with an increase in brain inflammation, oxidative stress and calcium. Administration of ruthenium red and pioglitazone has significantly attenuated PaD induced impairment of learning, memory, blood brain barrier permeability, endothelial function and biochemical parameters. It may be concluded that ruthenium red, a ryanodine receptor antagonist and pioglitazone, a PPAR-γ agonist may be considered as potent pharmacological agent for the management of PaD induced endothelial dysfunction and subsequent vascular dementia. Ryanodine receptor may be explored further for their possible benefits in vascular dementia.

Effects of Lactobacillus plantarum TWK10-Fermented Soymilk on Deoxycorticosterone Acetate-Salt-Induced Hypertension and Associated Dementia in Rats

Oxidative stress resulting from excessive production of reactive oxygen species is the major mediator of neuronal cell degeneration observed in neurodegenerative diseases, such as Alzheimer’s disease (AD) and vascular dementia (VaD). Additionally, hypertension has been shown to be a positive risk factor for VaD. Therefore, the objective of this study was to investigate the effects of Lactobacillus plantarum strain TWK10 (TWK10)-fermented soymilk on the protection of PC-12 cells in H₂O₂-, oxygen-glucose deprivation (OGD)- and deoxycorticosterone acetate (DOCA)-salt-induced rat models of VaD. Notably, the viabilities of H₂O₂-treated PC-12 cells and OGD model were significantly increased by treatment with TWK10-fermented soymilk ethanol extract (p < 0.05). In addition, oral administration of TWK10-fermented soymilk extract in DOCA-salt hypertension-induced VaD rats resulted in a significant decrease in blood pressure (p < 0.05), which was regulated by inhibiting ACE activity and promoting NO production, in addition to decreased escape latency and increased target crossing (p < 0.05). In conclusion, these results demonstrated that TWK10-fermented soymilk extract could improve learning and memory in DOCA-salt hypertension-induced VaD rats by acting as a blood pressure-lowering and neuroprotective agent.

Neuroprotective effect of selective DPP-4 inhibitor in experimental vascular dementia

Vascular risk factors are associated with a higher incidence of dementia. Diabetes mellitus is considered as a main risk factor for Alzheimer's disease and vascular dementia. Both forms of dementia are posing greater risk to the world population and are increasing at a faster rate. In the past we have reported the induction of vascular dementia by experimental diabetes. This study investigates the role of vildagliptin, a dipeptidyl peptidase-4 inhibitor in the pharmacological interdiction of pancreatectomy diabetes induced vascular endothelial dysfunction and subsequent vascular dementia in rats. Attentional set shifting and Morris water-maze test were used for assessment of learning and memory. Vascular endothelial function, blood brain barrier permeability, serum glucose, serum nitrite/nitrate, oxidative stress (viz. aortic superoxide anion, brain thiobarbituric acid reactive species and brain glutathione), brain calcium and inflammation (myeloperoxidase) were also estimated. Pancreatectomy diabetes rats have shown impairment of endothelial function, blood brain barrier permeability, learning and memory along with increase in brain inflammation, oxidative stress and calcium. Administration of vildagliptin has significantly attenuated pancreatectomy induced impairment of learning, memory, endothelial function, blood brain barrier permeability and biochemical parameters. It may be concluded that vildagliptin, a dipeptidyl peptidase-4 inhibitor may be considered as potential pharmacological agents for the management of pancreatectomy induced endothelial dysfunction and subsequent vascular dementia. The selective modulators of dipeptidyl peptidase-4 may further be explored for their possible benefits in vascular dementia.

The implications of angiotensin-converting enzymes and their modulators in neurodegenerative disorders: current and future perspectives

Angiotensin converting enzyme (ACE) is a dipeptidyl peptidase transmembrane bound enzyme. Generally, ACE inhibitors are used for the cardiovascular disorders. ACE inhibitors are primary agents for the management of hypertension, so these cannot be avoided for further use. The present Review focuses on the implications of angiotensin converting enzyme inhibitors in neurodegenerative disorders such as dementia, Alzheimer's disease, Parkinson's disease, Huntington's disease, amyotrophic lateral sclerosis, stroke, and diabetic neuropathy. ACE inhibitors such as ramipril, captopril, perindopril, quinapril, lisinopril, enalapril, and trandolapril have been documented to ameliorate the above neurodegenerative disorders. Neurodegeneration occurs not only by angiotensin II, but also by other endogenous factors, such as the formation of free radicals, amyloid beta, immune reactions, and activation of calcium dependent enzymes. ACE inhibitors interact with the above cellular mechanisms. Thus, these may act as a promising factor for future medicine for neurological disorders beyond the cardiovascular actions. Central acting ACE inhibitors can be useful in the future for the management of neuropathic pain due to following actions: (i) ACE-2 converts angiotensinogen to angiotensin(1-7) (hepatapeptide) which produces neuroprotective action; (ii) ACE inhibitors downregulate kinin B1 receptors in the peripheral nervous system which is responsible for neuropathic pain. However, more extensive research is required in the field of neuropathic pain for the utilization of ACE inhibitors in human.

Melatonin receptor and KATP channel modulation in experimental vascular dementia

Cerebrovascular and cardiovascular diseases are stated as important risk factors of vascular dementia (VaD) and other cognitive disorders. In the central nervous system, melatonin (MT1/MT2) as well as serotonin subtype 2C (5-HT2C) receptors is pharmacologically associated with various neurological disorders. Brain mitochondrial potassium channels have been reported for their role in neuroprotection. This study has been structured to investigate the role of agomelatine, a melatonergic MT1/MT2 agonist and nicorandil, a selective ATP sensitive potassium (KATP) channel opener in renal artery ligation (two-kidney-one-clip: 2K1C) hypertension induced endothelial dysfunction, brain damage and VaD. 2K1C-renovascular hypertension has increased mean arterial blood pressure (MABP), impaired memory (elevated plus maze and Morris water maze), endothelial function, reduced serum nitrite/nitrate and increased brain damage (TTC staining of brain sections). Furthermore, 2K1C animals have shown high levels of oxidative stress in serum (increased thiobarbituric acid reactive species-TBARS with decreased levels of glutathione-GSH, superoxide dismutase-SOD and catalase-CAT), in the aorta (increased aortic superoxide anion) and in the brain (increased TBARS with decreased GSH, SOD and CAT). 2K1C has also induced a significant increase in brain inflammation (myeloperoxidase-MPO levels), acetylcholinesterase activity (AChE) and calcium levels. Impairment in mitochondrial complexes like NADH dehydrogenase (complex-I), succinate dehydrogenase (complex-II) and cytochrome oxidase (complex-IV) was also noted in 2K1C animals. Administration of agomelatine, nicorandil and donepezil significantly attenuated 2K1C-hypertension induced impairments in memory, endothelial function, nitrosative stress, mitochondrial dysfunction, inflammation and brain damage. Therefore, modulators of MT1/MT2 receptors and KATP channels may be considered as potential agents for the management of renovascular hypertension induced VaD.

In vivo and in vitro attenuation of naloxone-precipitated experimental opioid withdrawal syndrome by insulin and selective KATP channel modulator

RATIONALE

Opiate exposure for longer duration develops state of dependence in humans and animals, which is revealed by signs and symptoms of withdrawal precipitated by opioid receptor antagonists. The sudden withdrawal of opioids produces a withdrawal syndrome in opioid-dependent subjects. Insulin and ATP-sensitive potassium (KATP) channel-mediated glucose homeostasis have been shown to modulate morphine withdrawal.

OBJECTIVE

Present study has been structured to investigate the role of insulin and pharmacological modulator of KATP channel (gliclazide) in experimental morphine withdrawal syndrome, both invivo and invitro.

METHODS

In this study, naloxone-precipitated morphine withdrawal syndrome in mice (invivo) as well as in rat ileum (invitro) were utilized to assess opioid withdrawal phenomenon. Morphine withdrawal syndromes like jumping and rearing frequency, forepaw licking, circling, fore paw tremor, wet dog shake, sneezing, overall morphine withdrawal severity (OMWS), serum glucose, brain malondialdehyde (MDA), glutathione (GSH), nitrite/nitrate, and calcium (Ca(+2)) were assessed.

RESULTS

Naloxone has significantly increased morphine withdrawal syndrome, both invivo and invitro. Insulin and gliclazide have significantly attenuated, naloxone induced behavioral changes like jumping and rearing frequency, forepaw licking, wet dog shake, sneezing, straightening, circling, OMWS, and various biochemical impairments such as serum glucose, brain MDA, GSH, nitrite/nitrate, and Ca(+2) in morphine-dependent animals (invivo). In vitro, insulin and gliclazide have significantly reduced naloxone-induced contraction in morphine-withdrawn rat ileum preparation.

CONCLUSIONS

Insulin and gliclazide (KATP channel blocker) have attenuated naloxone-precipitated morphine withdrawal syndrome, both invivo and invitro. Thus, insulin and KATP channel modulation may provide new avenues for research in morphine withdrawal.

Chronic infusion of lisinopril into hypothalamic paraventricular nucleus modulates cytokines and attenuates oxidative stress in rostral ventrolateral medulla in hypertension

The hypothalamic paraventricular nucleus (PVN) and rostral ventrolateral medulla (RVLM) play a critical role in the generation and maintenance of sympathetic nerve activity. The renin-angiotensin system (RAS) in the brain is involved in the pathogenesis of hypertension. This study was designed to determine whether inhibition of the angiotensin-converting enzyme (ACE) in the PVN modulates cytokines and attenuates oxidative stress (ROS) in the RVLM, and decreases the blood pressure and sympathetic activity in renovascular hypertensive rats. Renovascular hypertension was induced in male Sprague-Dawley rats by the two-kidney one-clip (2K1C) method. Renovascular hypertensive rats received bilateral PVN infusion with ACE inhibitor lisinopril (LSP, 10μg/h) or vehicle via osmotic minipump for 4weeks. Mean arterial pressure (MAP), renal sympathetic nerve activity (RSNA), and plasma proinflammatory cytokines (PICs) were significantly increased in renovascular hypertensive rats. The renovascular hypertensive rats also had higher levels of ACE in the PVN, and lower level of interleukin-10 (IL-10) in the RVLM. In addition, the levels of PICs, the chemokine MCP-1, the subunit of NAD(P)H oxidase (gp91(phox)) and ROS in the RVLM were increased in hypertensive rats. PVN treatment with LSP attenuated those changes occurring in renovascular hypertensive rats. Our findings suggest that the beneficial effects of ACE inhibition in the PVN in renovascular hypertension are partly due to modulation cytokines and attenuation oxidative stress in the RVLM.

Ameliorative Effect of a Selective Endothelin ETA Receptor Antagonist in Rat Model of L-Methionine-induced Vascular Dementia

The present study was designed to investigate the efficacy of selective ET_A receptor antagonist, ambrisentan on hyperhomocysteinemia-induced experimental vascular dementia. L-methionine was administered for 8 weeks to induce hyperhomocysteinemia and associated vascular dementia in male rats. Ambrisentan was administered to L-methionine-treated effect rats for 4 weeks (starting from 5^th to 8^th week of L-methionine treatment). On 52^nd day onward, the animals were exposed to the Morris water maze (MWM) for testing their learning and memory abilities. Vascular endothelial function, serum nitrite/nitrate levels, brain thiobarbituric acid reactive species (TBARS), brain reduced glutathione (GSH) levels, and brain acetylcholinesterase (AChE) activity were also measured. L-methionine-treated animals showed significant learning and memory impairment, endothelial dysfunction, decrease in/serum nitrite/nitrate and brain GSH levels along with an increase in brain TBARS levels and AChE activity. Ambrisentan significantly improved hyperhomocysteinemia-induced impairment of learning, memory, endothelial dysfunction, and changes in various biochemical parameters. These effects were comparable to that of donepezil serving as positive control. It is concluded that ambrisentan, a selective ET_A receptor antagonist may be considered as a potential pharmacological agent for the management of hyperhomocysteinemia-induced vascular dementia.

Pharmacological benefit of I(1)-imidazoline receptors activation and nuclear factor kappa-B (NF-κB) modulation in experimental Huntington's disease

Huntington's disease (HD), a neurodegenerative disorder, is characterized by progressive motor dysfunction, emotional disturbances, dementia, weight loss and anxiety. The tremendous amount of research work is required to identify new pharmacological agents of therapeutic utility to combat this condition. This study investigates the effect of selective modulator of I1-imidazoline receptor (moxonidine) as well as nuclear factor kappa-B (NF-κB) (natrium diethyl dithio carbamate trihydrate-NDDCT) on 3-nitropropionic acid (3-NPA) induced experimental HD condition. 3-NPA was used to induce mitochondrial damage and associated HD symptoms in rats. Anxiety was assessed using Elevated plus maze-EPM and learning-memory was assessed using EPM and Morris water maze-MWM. Different biochemical estimations were used to assess brain striatum oxidative stress (lipid peroxide, superoxide dismutase and catalase), nitric oxide levels (nitrite/nitrate), cholinergic activity (brain striatum acetyl cholinesterase activity), and mitochondrial enzyme complex (I, II and IV) activities. 3-NPA has induced anxiety, impaired learning-memory with a reduction in body weight, locomotor activity, grip strength. It has increased brain striatum acetylcholinesterase-AChE activity, oxidative stress (lipid peroxide, nitrite/nitrate, superoxide dismutase and catalase) and impaired mitochondrial complex enzyme (I, II and IV) activities. Tetrabenazine-TBZ (monoamine storage inhibitor) was used as positive control. Treatment with moxonidine, NDDCT and TBZ significantly attenuated 3-NPA induced reduction in body weight, locomotor activity, grip strength, anxiety as well as impaired learning and memory. Administration of these agents attenuated 3-NPA induced various biochemical impairments. Therefore, modulation of I1-imidazoline receptor as well as NF-κB may be considered as potential pharmacological agents for the management of 3-NPA induced HD.

Arsenic toxicity induced endothelial dysfunction and dementia: pharmacological interdiction by histone deacetylase and inducible nitric oxide synthase inhibitors

Arsenic toxicity has been reported to damage all the major organs including the brain and vasculature. Dementia including Alzheimer's disease (AD) and vascular dementia (VaD) are posing greater risk to the world population as it is now increasing at a faster rate. We have investigated the role of sodium butyrate, a selective histone deacetylase (HDAC) inhibitor and aminoguanidine, a selective inducible nitric oxide synthase (iNOS) inhibitor in pharmacological interdiction of arsenic toxicity induced vascular endothelial dysfunction and dementia in rats. Arsenic toxicity was done by administering arsenic drinking water to rats. Morris water-maze (MWM) test was used for assessment of learning and memory. Endothelial function was assessed using student physiograph. Oxidative stress (aortic superoxide anion, serum and brain thiobarbituric acid reactive species, brain glutathione) and nitric oxide levels (serum nitrite/nitrate) were also measured. Arsenic treated rats have shown impairment of endothelial function, learning and memory, reduction in serum nitrite/nitrate & brain GSH levels along with increase in serum & brain TBARS. Sodium butyrate as well as aminoguanidine significantly convalesce arsenic induced impairment of learning, memory, endothelial function, and alterations in various biochemical parameters. It may be concluded that arsenic induces endothelial dysfunction and dementia, whereas, sodium butyrate, a HDAC inhibitor as well as aminoguanidine, a selective iNOS inhibitor may be considered as potential agents for the management of arsenic induced endothelial dysfunction and dementia.

Pharmacological inhibition of inducible nitric oxide synthase (iNOS) and nicotinamide adenine dinucleotide phosphate (NADPH) oxidase, convalesce behavior and biochemistry of hypertension induced vascular dementia in rats

Cognitive disorders are likely to increase over the coming years (5-10). Vascular dementia (VaD) has heterogeneous pathology and is a challenge for clinicians. Current Alzheimer's disease drugs have had limited clinical efficacy in treating VaD and none have been approved by major regulatory authorities specifically for this disease. Role of iNOS and NADPH-oxidase has been reported in various pathological conditions but there role in hypertension (Hypt) induced VaD is still unclear. This research work investigates the salutiferous effect of aminoguanidine (AG), an iNOS inhibitor and 4'-hydroxy-3'-methoxyacetophenone (HMAP), a NADPH oxidase inhibitor in Hypt induced VaD in rats. Deoxycorticosterone acetate-salt (DOCA-S) hypertension has been used for development of VaD in rats. Morris water-maze was used for testing learning and memory. Vascular system assessment was done by testing endothelial function. Mean arterial blood pressure (MABP), oxidative stress [aortic superoxide anion, serum and brain thiobarbituric acid reactive species (TBARS) and brain glutathione (GSH)], nitric oxide levels (serum nitrite/nitrate) and cholinergic activity (brain acetyl cholinesterase activity-AChE) were also measured. DOCA-S treated rats have shown increased MABP with impairment of endothelial function, learning and memory, reduction in serum nitrite/nitrate & brain GSH levels along with increase in serum & brain TBARS, and brain AChE activity. AG as well as HMAP significantly convalesce Hypt induced impairment of learning, memory, endothelial function, and alterations in various biochemical parameters. It may be concluded that AG, an iNOS inhibitor and HMAP, a NADPH-oxidase inhibitor may be considered as potential agents for the management of Hypt induced VaD.