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.

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.

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.

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.

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.

Effect of hypobaric hypoxia on visual evoked potential at high altitude.

The effect of hypobaric hypoxia on visual evoked potential (VEP) was studied in 27 male volunteers at sea level (SL), during the 1st and 3rd weeks of their stay at high altitude (HA) of 3,500 m and in the 1st week of their return to the sea level (RSL). Exposure to high altitude (HA) led to significant changes in VEP. The N1 wave latency of both right and left eye was significantly increased (P<0.05) during 3rd week of stay at the altitude which persisted even after the return to the sea level. The latency of P1 wave of both right and left eye was higher in 3rd week at high altitude but not significant statistically. But the delay in P1 latency persisted in 1st week of their return to sea level which was significant (p<0.05) statistically as compared to sea level. The latency of N2 wave was significantly decreased (P<0.05) during the 1st week of stay at HA and returned back to basal value in the 3rd week of stay at HA in both right and left eye. However, the changes observed in NPN complex in terms of wave latencies were within the physiological limits. The amplitude of wave N1-P1 of both the right and left eye did not show any change. The changes observed reflect the process of acclimatisation to 3500m high altitude.

Effect of high altitude (HA) on event related brain potentials.

Event Related brain potentials (ERPs) were recorded in 15 subjects using standard auditory odd ball paradigm, in which subjects were presented a sequence of two distinguishable sound stimuli of that occurred frequently (frequently (frequent stimulus-non target) and the other infrequently (rare stimulus-target). These recordings were made at sea level (SL) and then the subjects were air lifted to 3500 m altitude (HA), where they stayed for 3 weeks. Their ERPs were recorded during the first and third week of stay at HA and on return to sea level (RSL). Data indicated impairment in cognitive function as a result of exposure to HA as depicted by increase in the latency of P3 which was significant during the 1st week of stay at HA compared to sea level. The P3 wave latency during the 3rd week of stay at HA showed an increase compared to SL but was not statistically significant. From the results it may be concluded that high altitude hypoxia induced slow processing of stimulus evaluation, may be responsible for increase in P3 latency. The difference in the latent period of P3 waves during the first and third week of stay at HA may be due to continuous stay at HA which might lead to the time dependent adaptive processes occurring with increasing duration of exposure to HA which may induce learning effects.

Effect of a carbohydrate supplement on feeding behaviour and exercise in rats exposed to hypobaric hypoxia.

The effect of a carbohydrate supplement, offered as a diet option, on feeding behaviour, body weight gain, and endurance exercise was studied in rats exposed to hypobaric hypoxia. Male albino rats (n = 35) were randomly divided into 5 groups; hypoxic supplemented and control groups; normoxic supplemented and control groups, and an untreated control group. After treadmill training for 5 days, the hypoxic groups were exposed to simulated high altitude equivalent to 6960 m for 18 days continuously. Food and water intakes, body weight and endurance exercise were recorded before and during the exposure period. Blood glucose, insulin, muscle and liver glycogen were assayed at the end of the exposure period. Hypobaric hypoxia resulted in a significant decrease in food and water intake, and body weight, and reduced endurance exercise capacity compared to the basal and normoxic group values. The carbohydrate supplement did not ameliorate the hypoxia-induced loss in body weight, but however, significantly delayed the onset of fatigue during exercise in the supplemented rats compared to the hypoxic control group.

Effect of high altitude on sensitivity to the taste of phenylthiocarbamide.

Sensitivity to the taste of phenylthiocarbamide (PTC) was studied using the Harris-Kalmus method in healthy human volunteers at sea level and then subsequently at an altitude of 3500 m over a period of 3 weeks, after which they were brought back to sea level. Blood sugar, insulin and blood cortisol levels were estimated weekly. The results indicated that, out of 51 subjects studied, 26 (55%) were PTC tasters at sea level. Eight of those unable to taste PTC at sea level tested as tasters at high altitude, and 2 of them reverted to being non-tasters on return to sea level. In the blood, an increase in cortisol and blood insulin levels was seen without any significant change in sugar levels. All the changes recorded at high altitude tended to return to basal values after re-induction to sea level. The study suggests that high-altitude hypoxia in some way, possibly involving changes in hormonal profile among other factors, causes an alteration in sensitivity to the taste of PTC, resulting in some of the individuals shifting to lower PTC sensitivity.

Effect of Sahaja yoga meditation on auditory evoked potentials (AEP) and visual contrast sensitivity (VCS) in epileptics.

The effect of Sahaja yoga meditation on 32 patients with primary idiopathic epilepsy on regular and maintained antiepileptic medication was studied. The patients were randomly divided into 3 groups: group I practiced Sahaja Yoga meditation twice daily for 6 months under proper guidance; group II practiced postural exercises mimicking the meditation for the same duration; and group III was the control group. Visual Contrast Sensitivity (VCS), Auditory Evoked Potentials (AEP), Brainstem Auditory Evoked Potentials (BAEP), and Mid Latency Responses (MLR) were recorded initially (0 month) and at 3 and 6 months for each group. There was a significant improvement in VCS following meditation practice in group I participants. Na, the first prominent negative peak of MLR and Pa, the positive peak following Na did not register changes in latency. The Na-Pa amplitude of MLR also showed a significant increase. There were no significant changes in the absolute and interpeak latencies of BAEP. The reduced level of stress following meditation practice may make patients more responsive to specific stimuli. Sahaja Yoga meditation appears to bring about changes in some of the electrophysiological responses studied in epileptic patients.

Hypobaric hypoxia and hedonic matrix in rats.

This study was carried out to evaluate the effect of continuous exposure to hypobaric hypoxia on the feeding behavior and taste responses of rats, under simulated conditions of a high altitude (HA) of 7,620 m for 21 h a day and consecutively for 18 d, which more closely resembles actual field conditions. Their food, water intake and body weight were recorded daily, and blood sugar was estimated once a week. All the parameters were recorded for a period of 18 d each, before, during, and after exposure to simulated HA. The results show a decrease in daily food and water intake and body weight, and mild hypoglycemia during hypoxic exposure. Single-bottle and two-bottle tests showed a preference for sweet solutions over water, citric acid, sodium chloride, and quinine sulfate during exposure. The two-bottle test showed a preference for glucose over calorically-inert saccharine. The continuous exposure in this study produced qualitatively similar but quantitatively accentuated results as compared to intermittent 6 h exposure contiguously for 21 d. High-altitude stress appears to influence food intake such that sensory cues assume greater significance during feeding behavior.

Effect of vitamin C in modulating the hypothermic influence on nerve conduction.

The study was carried out to evaluate the effect of different degrees of hypothermia on nerve conduction and the possible beneficial effect of vitamin C in the amelioration of the impairment in nerve conduction due to hypothermia. Sixty male Wistar rats, 225-250 g, were randomly divided into two equal groups of untreated controls and vitamin C treated experimental groups. Sciatic nerve conduction and nerve temperature (Tn) were recorded at different degrees of hypothermia by step-wise lowering of rectal temperature (Tr) from 38 to 20 degrees C. A regression analysis showed a positive linear relationship of Tr with nerve conduction velocity (NCV) and with Tn in both groups (p < 0.001). There was also a positive linear relationship between Tn and NCV in both groups: control, p < 0.001; experimental, p < 0.05. Comparisons between the regression equations of Tr with NCV, Tr with Tn, and Tn with NCV showed significant differences between the two groups (p < 0.001). There was no significant relationship between Tr and the amplitude of the action potential. Vitamin C may have a protective effect against the impairment of NCV due to hypothermia.

Effect of Sahaja yoga practice on seizure control & EEG changes in patients of epilepsy.

The effect of Sahaja yoga meditation on seizure control and electroencephalographic alterations was assessed in 32 patients of idiopathic epilepsy. The subjects were randomly divided into 3 groups. Group I (n = 10) practised Sahaja yoga for 6 months, Group II (n = 10) practised exercises mimicking Sahaja yoga for 6 months and Group III (n = 12) served as the epileptic control group. Group I subjects reported a 62 per cent decrease in seizure frequency at 3 months and a further decrease of 86 per cent at 6 months of intervention. Power spectral analysis of EEG showed a shift in frequency from 0-8 Hz towards 8-20 Hz. The ratios of EEG powers in delta (D), theta (T), alpha (A) and beta (B) bands i.e., A/D, A/D + T, A/T and A + B/D + T were increased. Per cent D power decreased and per cent A increased. No significant changes in any of the parameters were found in Groups II and III, indicating that Sahaja yoga practice brings about seizure reduction and EEG changes. Sahaja yoga could prove to be beneficial in the management of patients of epilepsy.

Brainstem auditory evoked potentials in epileptics on different anti-epileptic drugs.

The effects of anti-epileptic drugs (AEDs) on brainstem auditory evoked potentials (BAEPs) were studied on 32 female patients of epilepsy and 10 age-matched normal healthy females (NS). The patients were divided into 6 groups, those not receiving medication (drug free, DF) and those receiving AEDs: Phenytoin (PHT), Carbamazepine (CBZ), Phenobarbital (PB), a combination of PHT and PB and a combination of CBZ and PB. DF epileptics had shortened were V absolute latency (AL) and I-V interpeak latency (IPL) as compared to NS. Phenytoin and CBZ monotherapy produced a prolongation of wave III AL (by PHT only), wave V AL, wave I-III IPL and I-V IPL, as compared to DF epileptics. Phenytoin monotherapy also prolonged wave III AL and I-III IPL, as compared to NS. When PB in the dosage of 30-60 mg/d was used in combination with PHT the above mentioned changes were not observed. These findings indicate altered neuronal conduction and/or synaptic transmission in epileptics. Anti-epileptic drugs in the dosages studied, with exception of PHT appear to lead towards "normalization" of BAEPs.

Effect of Sahaja yoga practice on stress management in patients of epilepsy.

An attempt was made to evaluate the effect of Sahaja yoga meditation in stress management in patients of epilepsy. The study was carried out on 32 patients of epilepsy who were rendomly divided into 3 groups: group I subjects practised Sahaja yoga meditation for 6 months, group II subjects practised postural exercises mimicking Sahaja yoga and group III served as the epileptic control group. Galvanic skin resistance (GSR), blood lactate and urinary vinyl mandelic acid (U-VMA) were recorded at 0, 3 and 6 months. There were significant changes at 3 & 6 months as compared to 0 month values in GSR, blood lactate and U-VMA levels in group I subjects, but not in group II and group III subjects. The results indicate that reduction in stress following Sahaja yoga practice may be responsible for clinical improvement which had been earlier reported in patients who practised Sahaja yoga.