Surajit Sahu

Guanfacine is an effective countermeasure for hypobaric hypoxia-induced cognitive decline

Hypobaric hypoxia (HH), an environmental stress resulting from ascent to high altitude, affects perception, memory, judgment, and attention, resulting in degradation of many aspects of normal functioning. Alpha 2A adrenergic agonist, guanfacine proved to be beneficial in the amelioration of neurological outcomes of many neuropsychiatric disorders involving adrenergic imbalance and neurodegeneration. Adrenergic dysregulation and neuronal damage have been implicated in hypoxia-induced cognitive deficits, however, efficacy of guanfacine as a countermeasure for HH-induced cognitive decline remains to be evaluated. We, therefore, have studied the effect of this drug on the HH-induced cognitive deficits, adrenergic dysfunction and neuronal damage. Rats were exposed to HH at a simulated altitude of 25,000 feet for 7days and received an IM injection of either saline or guanfacine at a dose of 1mg/kg. Adrenergic transmission was evaluated by biomarkers i.e. norepinephrine (NE), dopamine (DA) and tyrosine hydroxylase (TH) in medial prefrontal cortex (PFC) by biochemical and immunohistochemical assays. Spine and dendritic morphology of pyramidal neurons in layer II of medial PFC was studied using Golgi-Cox staining and Neurolucida neuronal tracing. The cognitive performance was assessed by Delayed Alternation Task using a T-Maze. There was a significant reduction in HH-induced increases in NE, DA and TH levels with guanfacine treatment. Guanfacine rescued HH-induced dendritic atrophy and mushroom type spine loss. The spatial working memory deficits induced by HH were significantly ameliorated with guanfacine treatment. Furthermore, the cognitive performance showed a positive correlation with dendritic arbors and spine numbers. These results showed that the HH-induced cognitive decline is associated with adrenergic dysregulation and neuronal damage in layer II of medial PFC, and that guanfacine treatment during HH ameliorated these functional and morphological deficits. The study suggests a potential role of the alpha-2A adrenergic agonist, guanfacine, in amelioration of PFC dysfunction caused by high altitude exposure.

Caffeine and modafinil given during 48 h sleep deprivation modulate object recognition memory and synaptic proteins in the hippocampus of the rat

We aimed to evaluate the effect of caffeine/modafinil on sleep deprivation (SD) induced alterations in recognition memory and synaptic proteins. The data revealed a beneficial effect of caffeine/modafinil against deficit in the familiar object retrieval performance and object exploration ratio after 48 h SD. Caffeine treatment prevented the SD induced down-regulation of synaptophysin and synapsin I proteins with no change in PSD-95 protein in hippocampus. However, modafinil administration improved the down-regulation of synaptophysin, synapsin I and PSD-95 proteins in hippocampus. Hence, caffeine/modafinil can serve as counter measures in amelioration of SD induced consequences at behavioural and protein levels.

Valeriana wallichii root extract improves sleep quality and modulates brain monoamine level in rats

The present study was performed to investigate the effects of Valeriana wallichi (VW) aqueous root extract on sleep-wake profile and level of brain monoamines on Sprague-Dawley rats. Electrodes and transmitters were implanted to record EEG and EMG in freely moving condition and the changes were recorded telemetrically after oral administration of VW in the doses of 100, 200 and 300 mg/kg body weight. Sleep latency was decreased and duration of non-rapid eye movement (NREM) sleep was increased in a dose dependent manner. A significant decrease of sleep latency and duration of wakefulness were observed with VW at doses of 200 and 300 mg/kg. Duration of NREM sleep as well as duration of total sleep was increased significantly after treatment with VW at the doses of 200 and 300 mg/kg. VW also increased EEG slow wave activity during NREM sleep at the doses of 200 and 300 mg/kg. Level of norepinephrine (NE), dopamine (DA), dihydroxyphenylacetic acid (DOPAC), serotonin (5-HT) and hydroxy indole acetic acid (HIAA) were measured in frontal cortex and brain stem after VW treatment at the dose of 200mg/kg. NE and 5HT level were decreased significantly in both frontal cortex and brain stem. DA and HIAA level significantly decreased only in cortex. DOPAC level was not changed in any brain region studied. In conclusion it can be said that VW water extract has a sleep quality improving effect which may be dependent upon levels of monoamines in cortex and brainstem.

Anticonvulsant effect of Marsilea quadrifolia Linn. on pentylenetetrazole induced seizure: A behavioral and EEG study in rats

ETHNOPHARMACOLOGICAL RELEVANCE Marsilea quadrifolia Linn (MQ) extract has been used traditionally as sedative and antiepileptic drug in India. AIM OF THIS STUDY To investigate the anticonvulsive potential of MQ extracts by using behavior and electroencephalographic (EEG) analysis on pentylenetetrazole (PTZ) induced seizure model in rats. MATERIALS AND METHODS For anticonvulsant effect, 60minutes after administration of MQ, behavior and EEG were analyzed during PTZ (60mg/kg) induced seizures. Changes of EEG power, latency of onset of seizure, seizure severity score, and duration of epileptic seizure were determined. RESULTS Both the water and ethanol extract of MQ increased the latency of seizure but also decreased duration of epileptic seizure and seizure severity score. This reduction of seizure severity was also observed in EEG recording and EEG power analysis. The effectiveness of MQ ethanol extract is better than MQ water extract. CONCLUSION Both water and ethanol extract of MQ were effective in reducing the severity of behavioral and EEG seizures induced by PTZ in rats. This study justifies the traditional use of this plant in epilepsy.

Guanfacine ameliorates hypobaric hypoxia induced spatial working memory deficits

Hypobaric hypoxia (HH) observed at high altitude causes mild cognitive impairment specifically affecting attention and working memory. Adrenergic dysregulation and neuronal damage in prefrontal cortex (PFC) has been implicated in hypoxia induced memory deficits. Optimal stimulation of alpha 2A adrenergic receptor in PFC facilitates the spatial working memory (SWM) under the conditions of adrenergic dysregulation. Therefore the present study was designed to test the efficacy of alpha 2A adrenergic agonist, Guanfacine (GFC), to restore HH induced SWM deficits and PFC neuronal damage. The rats were exposed to chronic HH equivalent to 25,000ft for 7days in an animal decompression chamber and received daily treatment of GFC at a dose of 1mg/kg body weight via the intramuscular route during the period of exposure. The cognitive performance was assessed by Delayed Alternation Task (DAT) using T-Maze and PFC neuronal damage was studied by apoptotic and neurodegenerative markers. Percentage of correct choice decreased significantly while perseverative errors showed a significant increase after 7days HH exposure, GFC significantly ameliorated the SWM deficits and perseveration. There was a marked and significant increase in chromatin condensation, DNA fragmentation, neuronal pyknosis and fluoro Jade positive cells in layer II of the medial PFC in hypoxia exposed group, administration of GFC significantly reduced the magnitude of these changes. Modulation of adrenergic mechanisms by GFC may serve as an effective countermeasure in amelioration of prefrontal deficits and neurodegenerative changes during HH.

Modafinil improves event related potentials P300 and contingent negative variation after 24 h sleep deprivation

AIMS The efficacy of modafinil as a countermeasure in the reduction of cognitive decline following 24 h of sleep deprivation (SD) on subjective sleepiness scales, event-related potential (ERP) P300, and contingent negative variation (CNV) was evaluated. MAIN METHODS Eleven healthy males, age 25-30 years participated. The experiment was performed in five sessions on different days between 7 and 8a.m. Session 1, baseline recordings; Session 2, after one nights SD; Session 3, 48 h of recovery from SD; Session 4, after 1 week of Session 1, following one nights SD along with modafinil (400mg/day); Session 5, 48 h of recovery after SD+modafinil. KEY FINDINGS Subjective sleepiness scores increased significantly after SD as compared to baseline (P<0.01), but remained unaltered after modafinil supplementation. There was an increase in N100 and P300 peak latencies of ERP following SD (P<0.01), which was reduced with modafinil (P<0.05). There was an increase in CNV M100 and P300 peak latencies after SD (P<0.01) which decreased with the use of modafinil (P<0.05). The CNV reaction time increased following SD (P<0.01) and decreased with the use of modafinil (P<0.05). No significant effects on ERP N200, P200 latencies and P200, P300 amplitudes and CNV N100, M200 peak latencies and M100, M200 amplitudes were observed. SIGNIFICANCE The results strongly suggest that modafinil in a dose of 400mg/day, reduces the subjective sleepiness and cognitive decline following 24 h of SD.

Adenosine A1 receptor antagonist mitigates deleterious effects of sleep deprivation on adult neurogenesis and spatial reference memory in rats.

Sleep deprivation (SD) upsurges intracellular levels of adenosine, impairs adult neuronal cell proliferation (NCP) and cognition while caffeine, a non-selective adenosine A1 receptor (A1R) antagonist improves cognition and adult NCP during SD. We examined the selective antagonistic effects of adenosine A1R using 8-cyclopentyl-1,3-dimethylxanthine (8-CPT) on impairment of spatial reference memory and adult NCP during 48h SD. Adult male Sprague Dawley rats were sleep deprived for 48h, using an automatic cage vibrating stimulus based on animal activity. Spatial reference memory was tested as a measure of cognitive performance employing Morris Water Maze. Rats were given 8-CPT dissolved in 50% dimethyl sulfoxide (DMSO), twice daily (10mg/kg, i.p.) along with 5-bromo-2-deoxyuridine (BrdU) (50mg/kg/day, i.p.). The rats treated with 8-CPT showed significantly short mean latency and path-length to reach the platform compared to the SD rats. Consistent with these findings, 8-CPT-treated group was found to have significantly increased the number of BrdU, Ki-67 and doublecortin (DCX) positive cells. However, no significant difference was seen in NeuN expression in the Dentate Gyrus (DG). Brain-derived neurotropic factor (BDNF) expression in the DG and CA1 region was observed to decrease significantly after SD and be rescued by 8-CPT treatment. Furthermore, latency to reach platform showed a negative correlation with number of BrdU, DCX type-1 cells and BDNF expression in DG. Thus, it may be concluded that treatment with 8-CPT, an adenosine A1R antagonist during SD mitigates SD induced decline in spatial reference memory and adult NCP possibly via up regulation of BDNF levels in DG and CA1 regions.

Caffeine and Modafinil Ameliorate the Neuroinflammation and Anxious Behavior in Rats during Sleep Deprivation by Inhibiting the Microglia Activation

Background: Sleep deprivation (SD) plagues modern society due to the professional demands. It prevails in patients with mood and neuroinflammatory disorders. Although growing evidence suggests the improvement in the cognitive performance by psychostimulants during sleep-deprived conditions, the impending involved mechanism is rarely studied. Thus, we hypothesized that mood and inflammatory changes might be due to the glial cells activation induced modulation of the inflammatory cytokines during SD, which could be improved by administering psychostimulants. The present study evaluated the role of caffeine/modafinil on SD-induced behavioral and inflammatory consequences. Methods: Adult male Sprague-Dawley rats were sleep deprived for 48 h using automated SD apparatus. Caffeine (60 mg/kg/day) or modafinil (100 mg/kg/day) were administered orally to rats once every day during SD. Rats were subjected to anxious and depressive behavioral evaluation after SD. Subsequently, blood and brain were collected for biochemical, immunohistochemical and molecular studies. Results: Sleep deprived rats presented an increased number of entries and time spent in closed arms in elevated plus maze test and decreased total distance traveled in the open field (OF) test. Caffeine/modafinil treatment significantly improved these anxious consequences. However, we did not observe substantial changes in immobility and anhedonia in sleep-deprived rats. Caffeine/modafinil significantly down-regulated the pro- and up-regulated the anti-inflammatory cytokine mRNA and protein expression in the hippocampus during SD. Similar outcomes were observed in blood plasma cytokine levels. Caffeine/modafinil treatment significantly decreased the microglial immunoreactivity in DG, CA1 and CA3 regions of the hippocampus during SD, however, no significant increase in immunoreactivity of astrocytes was observed. Sholl analysis signified the improvement in the morphological alterations of astrocytes and microglia after caffeine/modafinil administration during SD. Stereological analysis demonstrated a significant improvement in the number of ionized calcium binding adapter molecule I (Iba-1) positive cells (different states) in different regions of the hippocampus after caffeine or modafinil treatment during SD without showing any significant change in total microglial cell number. Eventually, the correlation analysis displayed a positive relationship between anxiety, pro-inflammatory cytokines and activated microglial cell count during SD. Conclusion: The present study suggests the role of caffeine or modafinil in the amelioration of SD-induced inflammatory response and anxious behavior in rats. Highlights - SD induced mood alterations in rats. - Glial cells activated in association with the changes in the inflammatory cytokines. - Caffeine or modafinil improved the mood and restored inflammatory changes during SD. - SD-induced anxious behavior correlated with the inflammatory consequences.

Guanfacine promotes neuronal survival in medial prefrontal cortex under hypobaric hypoxia

High altitude hypobaric hypoxia (HH) affects prefrontal cognitive and executive functions. Guanfacine, alpha 2A adrenoceptor agonist ameliorates the neurological outcomes of high altitude exposure and associated prefrontal neurodegeneration. However, the molecular mechanism underlying the neuroprotective effect of guanfacine following HH remains elusive. Altered balance of pro and anti-apoptotic proteins have been implicated in the beneficial effect of guanfacine to enhance neuronal survival. We examined the effects of guanfacine on expression of some key neurotropic and cytoskeletal proteins following HH. Male rats were exposed to simulated altitude of 7620 m and received an intramuscular injection of either saline or guanfacine at a dose of 1mg/kg for 7 consecutive days. Differential expression of desired proteins was evaluated in layer II of medial prefrontal cortex (PFC) by biochemical and immunohistochemical assays. Guanfacine treatment significantly increased the expression of BDNF in layer II of the medial PFC during normoxia and HH. Moreover, there was a negative correlation of this neurotropic factor with neurodegeneration of pyramidal cells present in this layer of medial PFC. We found a significant decrease in Caspase3 and Bax while a significant increase in Bcl2 with guanfacine treatment during HH. Further, change in Bax to Bcl2 ratio was in correlation with Caspase3 expression in layer II of the medial PFC, indicating that Caspase3 is responsible for Bcl2 cleavage and hence modulation of apoptosis. Guanfacine treatment induced a marked and significant increase in MAP2 and Spinophilin expression in dendritic arbors and spines respectively. Interestingly, alteration in these cytoskeletal proteins was accompanied by simultaneous changes in morphological parameters of dendrites in layer II of medial PFC. Guanfacine modulates the neurotropic, cytoskeletal, pro and anti-apoptotic protein expression in medial PFC under HH and therefore serve as a countermeasure in the amelioration of HH induced alteration in these proteins.

Correct Laminar Positioning in the Neocortex Influences Proper Dendritic and Synaptic Development

Abstract The neocortex is a 6-layered laminated structure with a precise anatomical and functional organization ensuring proper function. Laminar positioning of cortical neurons, as determined by termination of neuronal migration, is a key determinant of their ability to assemble into functional circuits. However, the exact contribution of laminar placement to dendrite morphogenesis and synapse formation remains unclear. Here we manipulated the laminar position of cortical neurons by knocking down doublecortin (Dcx), a crucial effector of migration, and show that misplaced neurons fail to properly form dendrites, spines, and functional glutamatergic and GABAergic synapses. We further show that knocking down Dcx in properly positioned neurons induces similar but milder defects, suggesting that the laminar misplacement is the primary cause of altered neuronal development. Thus, the specific laminar environment of their fated layers is crucial for the maturation of cortical neurons, and influences their functional integration into developing cortical circuits.