Pradeep Sahota

Adenosine and the homeostatic control of sleep: Effects of A1 receptor blockade in the perifornical lateral hypothalamus on sleep–wakefulness

The orexinergic neurons of the lateral hypothalamus (LH) are critical for wakefulness [McCarley RW (2007) Neurobiology of REM and NREM sleep. Sleep Med 8:302-330]. Recent evidence suggests that adenosine (AD), a homeostatic sleep factor, may act via A1 receptor (A1R) to control orexinergic activity and regulate sleep-wakefulness [Thakkar MM, Winston S, McCarley RW (2002) Orexin neurons of the hypothalamus express adenosine A1 receptors. Brain Res 944:190-194; Liu ZW, Gao XB (2006) Adenosine inhibits activity of hypocretin/orexin neurons via A1 receptor in the lateral hypothalamus: a possible sleep-promoting effect. J Neurophysiol]. To evaluate the role of AD in the orexinergic LH and its influences on sleep-wakefulness, we designed two experiments in freely behaving rats: First, we bilaterally microinjected 1,3-dipropyl-8-phenylxanthine (DPX) (1.5 pmol and 15 pmol), a selective A1R antagonist into the LH during the light cycle and examined its effect on spontaneous sleep-wakefulness. Second, we performed 6 h of sleep deprivation. Thirty minutes before the animals were allowed to enter recovery sleep, 15 pmol of DPX was bilaterally microinjected into the LH and its effects on recovery sleep were monitored. Microinjection of DPX into the orexinergic LH produced a significant increase in wakefulness with a concomitant reduction in sleep, both during spontaneous bouts of sleep-wakefulness and during recovery sleep. Local administration of DPX into the LH produced a significant increase in the latency to non-REM sleep during recovery sleep. However, total slow wave (delta) activity during non-REM sleep phase of recovery sleep remained unaffected after DPX treatment. This is the first study that implicates endogenous adenosine to have a functional role in controlling orexinergic tone and influencing the homeostatic regulation of sleep-wakefulness.

Role of adenosine and wake-promoting basal forebrain in insomnia and associated sleep disruptions caused by ethanol dependence.

J. Neurochem. (2010) 115, 782–794.

Effects of ethanol on extracellular levels of adenosine in the basal forebrain: An in vivo microdialysis study in freely behaving rats

BACKGROUND Adenosine is implicated to play a pivotal role in mediating many neuronal responses to ethanol. While in vitro studies performed in cell culture have demonstrated that acute ethanol exposure increases extracellular adenosine levels, this effect has not been demonstrated, in vivo, in the brain. We performed an in vivo microdialysis study to examine the effects of local ethanol perfusion on extracellular levels of adenosine in the basal forebrain (BF). METHODS Under sterile conditions and using a standard surgical protocol, adult male Sprague-Dawley rats were implanted with unilateral microdialysis guide cannula targeted toward the BF. Following postoperative recovery, the microdialysis probe was inserted. After allowing at least 12 to 16 hours for probe insertion recovery, the experiment was begun. Artificial cerebrospinal fluid (aCSF) was perfused (0.7 microl/min) for 80 minutes, and 4 x 20-minute pre-ethanol baseline samples were collected. Subsequently, 30, 100, and 300 mM doses of ethanol were perfused. Each ethanol dose was perfused for 80 minutes, and 4 x 20-minute samples were collected. Finally, aCSF was perfused, and 4 x 20 postethanol samples were collected. Adenosine in the microdialysate was separated and measured with HPLC coupled with an UV detector. On completion, the animals were euthanized, brain removed and processed for histology. RESULTS Local ethanol perfusion in the BF produced a significant increase in extracellular adenosine with the highest dose of 300 mM ethanol producing a 4-fold increase. Cresyl violet (Nissl) staining did not indicate any toxic damage in the area surrounding the probe tip. Choline acetyltransferase immunohistochemistry revealed that all microdialysis probe sites were localized in the BF. CONCLUSION Our study is the first to demonstrate that ethanol acts directly in the brain to increase extracellular adenosine.

Role of Wake-Promoting Basal Forebrain and Adenosinergic Mechanisms in Sleep-Promoting Effects of Ethanol

BACKGROUND Ethanol intake has significant impact on sleep. However, the cellular substrates responsible for sleep promotion following ethanol intake are unknown. The purine nucleoside, adenosine, is responsible for mediating many neuronal and behavioral responses to ethanol. Studies performed in cell cultures suggest that ethanol inhibits equilibrative nucleoside transporter 1 to block the reuptake of adenosine resulting in increased extracellular adenosine. Adenosine also has a pivotal role in sleep regulation. Adenosine acts via A1 receptor to inhibit the wake-promoting neurons of the basal forebrain (BF) resulting in the promotion of sleep. Is ethanol-induced sleep associated with the inhibition of the BF wake-promoting neurons? Do adenosinergic mechanisms in the BF have a role in sleep-promoting effects of ethanol? METHODS To address these questions, we performed 3 experiments in Sprague-Dawley rats. First, we verified the effect of ethanol on sleep promotion. Second, we evaluated the effect of ethanol on c-Fos expression (a marker of neuronal activation) in the BF wake-promoting neurons and third we monitored the effects of A1 receptor blockade in the BF on ethanol-induced sleep. RESULTS Significant increase in non-rapid eye movement (NREM) sleep with a concomitant decrease in wakefulness was observed during the first 12 hours postethanol. REM sleep remained unaffected. Ethanol administration caused a significant decrease in the number of BF wake-promoting neurons with c-Fos immunoreactivity. Bilateral microinjections of a selective A1R receptor antagonist 8-cyclopentyl-1, 3-dipropylxanthine into the BF significantly attenuated sleep-promoting effects of ethanol. CONCLUSION These results suggest that the inhibition of BF wake-promoting neurons by adenosinergic mechanism may be responsible for the sleep promoting effects of ethanol. We believe our study is the first to investigate the cellular mechanisms responsible for the somnogenic effects of ethanol.

Role of Adenosine and the Orexinergic Perifornical Hypothalamus in Sleep-Promoting Effects of Ethanol

STUDY OBJECTIVES Strong clinical and preclinical evidence suggests that acute ethanol promotes sleep. However, very little is known about how and where ethanol acts to promote sleep. We hypothesized that ethanol may induce sleep by increasing extracellular levels of adenosine and inhibiting orexin neurons in the perifornical hypothalamus. DESIGN Experiments 1 and 2: Within-Subject Design; Experiment 3: Between-Subject Design. SETTING N/A. PATIENTS OR PARTICIPANTS N/A. INTERVENTIONS N/A. MEASUREMENTS AND RESULTS Using adult male Sprague-Dawley rats as our animal model, we performed three experiments to test our hypothesis. Our first experiment examined the effect of A1 receptor blockade in the orexinergic perifornical hypothalamus on sleep- promoting effects of ethanol. Bilateral microinjection of the selective A1 receptor antagonist 1,3-dipropyl-8-phenylxanthine (500 μM; 250 nL/side) into orexinergic perifornical hypothalamus significantly reduced nonrapid eye movement sleep with a concomitant increase in wakefulness, suggesting that blockade of adenosine A1 receptor attenuates ethanol-induced sleep promotion. Our second experiment examined adenosine release in the orexinergic perifornical hypothalamus during local ethanol infusion. Local infusion of pharmacologically relevant doses of ethanol significantly and dose-dependently increased adenosine release. Our final experiment used c-Fos immunohistochemistry to examine the effects of ethanol on the activation of orexin neurons. Acute ethanol exposure significantly reduced the number of orexin neurons containing c-Fos, suggesting an inhibition of orexin neurons after ethanol intake. CONCLUSIONS Based on our results, we believe that ethanol promotes sleep by increasing adenosine in the orexinergic perifornical hypothalamus, resulting in A1 receptor-mediated inhibition of orexin neurons.

Penumbra, the basis of neuroimaging in acute stroke treatment: Current evidence

In modern medicine brain imaging is an essential prerequisite not only to acute stroke triage but also to determining the specific therapy indicated. This article reviews the need for imaging the brain in acute stroke, penumbral pathophysiology, penumbral imaging techniques, as well as current status of various imaging modalities that are being employed to select patients for specific therapeutic approaches.

Sleep–wakefulness in alcohol preferring and non-preferring rats following binge alcohol administration

The alcohol-preferring (P) rat is a valid animal model of alcoholism. However, the effect of alcohol on sleep in P or alcohol non-preferring (NP) rats is unknown. Since alcohol consumption has tremendous impact on sleep, the present study compared the effects of binge alcohol administration on sleep-wakefulness in P and NP rats. Using standard surgical procedures, the P and NP rats were bilaterally implanted with sleep recording electrodes. Following post-operative recovery and habituation, pre-ethanol (baseline) sleep-wakefulness was electrographically recorded for 48 h. Subsequently, ethanol was administered beginning with a priming dose of 5 g/Kg followed by two doses of 2 g/Kg every 8 h on the first day and three doses of 3 g/Kg/8 h on the second day. On the following day (post-ethanol), undisturbed sleep-wakefulness was electrographically recorded for 24 h. Our initial results suggest that, during baseline conditions, the time spent in each of the three behavioral states: wakefulness, non-rapid eye movement (NREM) sleep and REM sleep, was comparable between P and NP rats. However, the P rats were more susceptible to changes in sleep-wakefulness following 2 days of binge ethanol treatment. As compared to NP rats, the P rats displayed insomnia like symptoms including a significant reduction in the amount of time spent in NREM sleep coupled with a significant increase in wakefulness on post-ethanol day. Subsequent analysis revealed that binge ethanol induced increased wakefulness and reduced NREM sleep in P rats occurred mainly in the dark period. This is the first study that: (1) demonstrates spontaneous sleep-wake profile in P and NP rats, and (2) compares the effects of binge ethanol treatment on sleep in P and NP rats. Our results suggest that, as compared to NP rats, the P rats were more susceptible to sleep disruptions after binge ethanol treatment. In addition, the P rats exhibited insomnia-like symptoms observed during abstinence from alcohol in human subjects.

Rapid tolerance development to the NREM sleep promoting effect of alcohol.

STUDY OBJECTIVES Alcohol tolerance is a major contributor towards the development of alcohol dependence. Does alcohol intake result in rapid tolerance development to alcohol induced NREM sleep promotion? This has never been examined. Our objective was to examine whether two bouts of alcohol consumption on consecutive days results in rapid tolerance development to alcohol-induced NREM sleep promotion. DESIGN N/A. SETTING N/A. PATIENTS OR PARTICIPANTS C57BL/6J mice. INTERVENTIONS Mice (N = 5) were implanted with sleep electrodes using standard surgical conditions. Following postoperative recovery and habituation, the experiment was begun. On baseline day, water bottle changes were performed at 10:00 (3 h after dark onset) and 14:00 to mimic conditions during alcohol consumption days. On next 2 days, (Days 1 and 2) mice were allowed to self-administer alcohol (20% v/v) for 4 h beginning at 10:00 and ending at 14:00. Sleep-wakefulness was continuously recorded from 10:00 to 18:00 (8 h; 4 h during alcohol + 4 h post-alcohol) on all 3 days. MEASUREMENTS AND RESULTS Although mice consumed comparable amounts of alcohol on Days 1 and 2, NREM sleep and wakefulness were significantly and differentially affected during 4 h post-alcohol period. A robust alcohol-induced NREM sleep promotion was observed on Day 1. However, no such sleep promotion was observed on Day 2, suggesting rapid tolerance development. CONCLUSIONS Our study is the first to demonstrate that alcohol consumption for two consecutive days results in development of rapid tolerance to alcohol-induced sleep promotion.

Psychogenic non-epileptic seizures: A challenging entity

Psychogenic non-epileptic seizures (PNES) are commonly encountered in neurologic practice. They are often misdiagnosed as epileptic seizures and treated as such for several years before a correct diagnosis is established. Such a misdiagnosis has the potential to expose patients to undue risk through several anti-epileptic drugs (AEDs). Patients are also affected in other ways, such as by financial consequences and the limitation of certain daily activities. In this review, we present the contemporary opinion of PNES with attention to clinically relevant salient features and management strategies.

Acute binge alcohol administration reverses sleep-wake cycle in Sprague Dawley rats.

BACKGROUND Binge alcohol drinking is among the most common pattern of alcohol consumption in our society. Binge alcohol consumption has serious negative consequence on mental and physical health. Although alcohol consumption is known to have profound impact on sleep, it is yet unknown as to how binge alcohol affects/alters sleep-wakefulness. The objective of this study was to examine the effect of acute binge alcohol administration on sleep-wakefulness. METHODS Male Sprague Dawley rats were used in the study. Under standard aseptic surgical conditions, rats (N = 7) were implanted with sleep-recording electrodes. After postoperative recovery and habituation, baseline sleep-wakefulness was recorded. Subsequently, rats were exposed to binge alcohol treatment as follows: One hour before light onset, a priming dose of 5 g/kg of alcohol was administered followed by 2 subsequent doses (adjusted based on the intoxication level of the rat) approximately 8 hours apart. Sleep-wakefulness was continuously recorded for 3 days post-binge. RESULTS Acute binge alcohol administration had no significant effect on sleep-wakefulness on post-binge Day 1. However, on post-binge Day 2, after blood alcohol concentration (BAC) was 0, sleep disruptions were observed manifested by a reversal of sleep-wakefulness as evident from insomnia-like symptoms (significant increase in wakefulness; significant reduction in nonrapid eye movement [NREM] sleep) during the normal sleep (light) period and excessive sleep (significant increase in NREM sleep) during the normal active (dark) period similar to excessive daytime sleepiness in humans. All sleep-wakefulness changes were normalized on Day 3 post-binge. CONCLUSIONS Alcohol hangover is defined as the presence of unpleasant symptoms that peak when BAC is 0. Our results suggest that the reversal of sleep-wakefulness accompanies alcohol hangover after binge alcohol administration.