Acute sleep deprivation induces synaptic remodeling at the soleus muscle neuromuscular junction in rats

Sleep is important for cognitive and physical performance. Sleep deprivation not only affects neural functions but also results in muscular fatigue. A good night's sleep reverses these functional derangements caused by sleep deprivation. The role of sleep in brain function has been extensively studied. However, its role in neuromuscular junction (NMJ) or skeletal muscle morphology is sparsely addressed although skeletal muscle atonia and suspended thermoregulation during rapid eye movement sleep possibly provide a conducive environment for the muscle to rest and repair; somewhat similar to slow-wave sleep for synaptic downscaling. In the present study, we have investigated the effect of 24 h sleep deprivation on the NMJ morphology and neurochemistry using electron microscopy and immunohistochemistry in the rat soleus muscle. Acute sleep deprivation altered synaptic ultra-structure viz. mitochondria, synaptic vesicle, synaptic proteins, basal lamina, and junctional folds needed for neuromuscular transmission. Further acute sleep deprivation showed the depletion of the neurotransmitter acetylcholine and the overactivity of its degrading enzyme acetylcholine esterase at the NMJ. The impact of sleep deprivation on synaptic homeostasis in the brain has been extensively reported recently. The present evidence from our studies shows new information on the role of sleep on the NMJ homeostasis and its functioning.

1146 SLEEP DEPRIVATION INDUCES AGEING-LIKE CHANGES IN ANTIGRAVITY MUSCLES OF YOUNG ADULT MALE WISTAR RATS

Introduction

Poor muscle health is associated with a series of chronic and metabolic conditions that are prevalent in individuals who chronically experience poor-quality sleep. But there is no study deciphering the role of sleep deprivation on muscle ageing. Therefore, in the present study we have measured the ultrastructure, histopathology, and oxidative stressors in soleus muscle of wistar rat after sleep deprivation and recovery sleep.

Material and Methods

The experiments were conducted in 18 rats of three groups. Group I rats had normal sleep wake cycle, Group II rats were subjected to 24 h sleep deprivation (SD) by gentle handling method1 and Group III rats had recovery sleep after 24 h SD. At the end of the sleep, sleep deprivation and recovery period, soleus muscle tissue was collected for ultrastructural, histological and oxidative stress markers. Oxidative damage was assessed by lipid peroxidation, catalase activity, reduced glutathione and nuclear labelling of 8-OHdG. The study was conducted as per the guidelines of the Institutional Animal Ethics Committee (960/IAEC/16).

Results

The data demonstrated that SD leads to ultrastructural changes in soleus muscle which includes sarcolemmal and mitochondrial alterations. In case of histopathological and histomorphological changes there was signs of tissue degeneration, inflammatory infiltrate in type I fibres and muscle atrophy was observed in soleus muscles. There was significant increase in level of 8-OHdG (p=0.02) and malondialdehyde in 24h SD (p=0.02) than control and recovery sleep groups. Moreover, the catalase activity and reduced glutathione level was significantly decreased in 24h SD group (p≤0.02) than control and recovery sleep.

Conclusion

24hr sleep deprivation leads to an ageing like state in the skeletal muscle, which was recovered after sleep rebound.

Electrophysiological Evidence of Local Sleep During Yoga Nidra Practice

Background and Objectives

Yoga nidra is a technique sages use to self-induce sleep. Classically, sleep is characterized by three cardinal electrophysiological features, namely, electroencephalography (EEG), electromyography (EMG), and electrooculography (EOG). As the literature on electrophysiological characterization of Yoga nidra is lacking, it is not known whether it is a sleep or awake state. The objective of the study was to electrophysiologically characterize yoga nidra practice.

Materials and Methods

Thirty subjects underwent five initial supervised yoga nidra sessions and then continued practice on their own. The subjects completed their sleep diaries for 2 weeks before and during the intervention. The electrophysiological characterization was done after 2 weeks of yoga nidra practice using 19 EEG channels polysomnography for pre-yoga nidra, yoga nidra practice and post-yoga nidra. Polysomnographic data were scored for sleep-wake stages as per standard criteria. Power spectral density (PSD) was calculated from various frequency bands in different time bins. EEG data were grouped by areas, namely, central, frontal, prefrontal, parietal, temporal, and occipital in time bins. Sleep diary parameters were also compared for pre-post-yoga nidra training.

Results

After 2 weeks of yoga nidra practice, awake was scored throughout the session (n = 26). PSD results (mean difference in dB between different time bins; P value) showed significant changes. When compared to pre-yoga nidra, there was an increase in delta power in the central area (1.953; P = 0.033) and a decrease in the prefrontal area (2.713; P = 0.041) during yoga nidra. Sleep diary showed improvement in sleep duration (P = 0.0001), efficiency (P = 0.0005), quality (P = 0.0005), and total wake duration (P = 0.00005) after 2 weeks of practice.

Interpretations and Conclusions

Yoga nidra practice in novices is electrophysiologically an awake state with signs of slow waves locally, often referred to as local sleep.

Clinical Trial

Clinical Trial Registry of India, http://www.ctri.nic.in/Clinicaltrials/pmaindet2.php? trialid = 6253, 2013/05/003682.

Yoga nidra practice shows improvement in sleep in patients with chronic insomnia: A randomized controlled trial

Background Yoga nidra is practised by sages for sleep. The practice is simple to use and has been clearly laid out, but its role in the treatment of chronic insomnia has not been well studied. Methods In this randomized parallel-design study conducted during 2012-16, we enrolled 41 patients with chronic insomnia to receive conventional intervention of cognitive behavioural therapy for insomnia (n=20) or yoga nidra (n=21). Outcome measures were both subjective using a sleep diary and objective using polysomnography (PSG). Salivary cortisol levels were also measured. PSG was done before the intervention in all patients and repeated only in those who volunteered for the same. Results Both interventions showed an improvement in subjective total sleep time (TST), sleep efficiency, wake after sleep onset, reduction in total wake duration and enhancement in subjective sleep quality. Objectively, both the interventions improved TST and total wake duration and increased N1% of TST. Yoga nidra showed marked improvement in N2% and N3% in TST. Salivary cortisol reduced statistically significantly after yoga nidra (p=0.041). Conclusion Improvement of N3 sleep, total wake duration and subjective sleep quality occurred following yoga nidra practice. Yoga nidra practice can be used for treatment of chronic insomnia after supervised practice sessions.

Muscle temperature is least altered during total sleep deprivation in rats

It has often been said that the brain is mostly benefitted from sleep. To understand the importance of sleep, extensive studies on other organs are too required. One such unexplored area is the understanding of muscle physiology during the sleep-wake cycle. Changes in muscle tone with different sleep phases are evident from the rapid eye movement sleep muscle atonia. There is variation in brain and body temperature during sleep stages, the brain temperature being higher during rapid eye movement sleep than slow-wave sleep. However, the change in muscle temperature with different sleep stages is not known. In this study, we have implanted pre-calibrated K-type thermocouples in the hypothalamus and the dorsal nuchal muscle, and a peritoneal transmitter to monitor the hypothalamic, muscle, and body temperature respectively in rats during 24 h sleep-wake cycle. The changes in muscle, body, and hypothalamic temperature during total sleep deprivation were also monitored. During normal sleep-wake stages, the temperature in the decreasing order was that of the hypothalamus, body, and muscle. Total sleep deprivation by gentle handling caused a significant increase in hypothalamic and body temperature, while there was least change in the muscle temperature. The circadian rhythm of the hypothalamic and body temperature in the sleep-deprived rats was disrupted, while the same was preserved in the muscle temperature. The results of our study show that muscle atonia during rapid eye movement sleep is a physiologically regulated thermally quiescent muscle state offering a conducive environment for muscle rest and repair.

Mediodorsal thalamus lesion increases paradoxical sleep in rats

INTRODUCTION

The mediodorsal thalamic nucleus has extensive connections with prefrontal cortex, which is considered as seat of cognition. It also receives connections from sleep-wakefulness regulating areas in the brainstem and hypothalamus. Decreased volume and degeneration of mediodorsal thalamic nuclei have been reported in schizophrenia and fatal familial insomnia, respectively. In both conditions, the sleep is abnormal.

OBJECTIVE

To study the role of mediodorsal thalamic nuclei in sleep wakefulness in rats.

MATERIAL AND METHODS

Neurotoxic lesion of mediodorsal thalamic nuclei with ibotenic acid was performed in adult male Wistar rats and sleep wakefulness was recorded. The recordings were taken on 2nd, 7th and 14th days after lesion and compared with the baseline recordings. In order to study the diurnal changes, lesion recordings were of 24h duration. We also performed L-glutamate excitation of mediodorsal thalamic nuclei in another set of animals. After L-glutamate microinjection, sleep wakefulness was recorded for 4h. The recordings were obtained in a digital acquisition system (BSL 4.0 MP 36, Biopac Systems, Inc., USA).

RESULTS

In the present investigation, ibotenic acid lesion of mediodorsal thalamic nuclei reduced the wakefulness and increased paradoxical sleep, which contradicts the reports from earlier lesion studies in cats. Glutamate excitation of mediodorsal thalamic nuclei produced prolonged wakefulness.

DISCUSSION

The results suggest that the mediodorsal thalamic nuclei augments arousal in the ascending reticular wake promoting pathways in contrast to the earlier reports that mediodorsal thalamic nucleus is involved in generation of slow wave sleep. The present study adds another evidence for the role of thalamus in sleep-wake regulation.

Acute sleep deprivation elevates brain and body temperature in rats

Available sleep deprivation studies lack data on simultaneous changes in hypothalamic, cortical and body temperature during sleep deprivation and recovery. Ten adult male Wistar rats chronically implanted with electroencephalogram, electro-oculogram and electromyogram electrodes for recording sleep were used in this study. Hypothalamic and cortical temperatures were measured by pre-implanted thermocouples. A radio transmitter (TA10TAF-40, DSI USA) was implanted intraperitoneally to measure body temperature. All the temperatures were measured simultaneously at 15-s intervals during baseline conditions, sleep deprivation and recovery sleep. Sleep deprivation was carried out for 24 hr by the gentle handling method; however, sleep and temperature were only recorded during the first 12 hr of deprivation. During sleep deprivation the body, hypothalamic and cortical temperatures increased significantly as compared to baseline. During recovery sleep, body and cortical temperature recovered earlier than the hypothalamic temperature. Hypothalamic temperature remained higher than the baseline values throughout 12 hr of recovery sleep. In the recovery sleep, cortical temperature decreased immediately and reached near baseline by 4 hr. We observed a quicker return of cortical temperature towards control temperature during recovery sleep compared with hypothalamic and body temperature. The results of the present study show that acute sleep deprivation results in a rise in both cortical and hypothalamic temperature, along with body temperature. A rise in cortical temperature may be a contributing factor for cognitive dysfunction resulting from sleep deprivation.

Intragastric administration of glutamate increases REM sleep in rats

Monosodium glutamate, a umami taste substance is commonly used flavor enhancer. The effect of intragastric administration of 1.5 ml of 0.12M monosodium glutamate on sleep-wake was studied in 10 adult male Wistar rats. Sleep-wake parameters were recorded through chronically implanted electroencephalogram, electrooculogram and electromyogram electrodes using a digital recording system (BIOPAC system Inc. BSL PRO 36, USA). The sleep-wake was recorded for 6h after the intragastric administration of either glutamate or saline. Sleep-wake stages were analyzed as wake, slow wave sleep and REM sleep. Compared to saline, intragastric administration of glutamate significantly increased REM sleep duration and episode frequency. REM sleep duration was increased in all the three 2h bins, 10:00-12:00 h (p=0.037), 12:00-14:00 h (p=0.037) and 14:00-16:00 h (p=0.007). The slow wave sleep and total sleep time were not affected. It is concluded that intragastric glutamate administration increases REM sleep.

Hypothalamic temperature: a key regulator in homeostatic restoration of sleep during chronic cold exposure in rats

Exposure to cold ambient temperature (Ta) affects sleep-wake (S-W) state. The vigilance states on the other hand influence thermal status of the animals. Simultaneous recording of body temperature (Tb) with S-W is crucial to understand the homeostatic relationship between the two. In the present study we recorded both Tb and hypothalamic temperature (Thy) along with S-W, during acute and chronic exposure to mild cold (Ta). Electrooculogram (EOG), electroencephalogram (EEG) and electromyogram (EMG) electrodes were chronically implanted in rats to assess S-W. A thermocouple, near the preoptic area, and radio transmitter in the peritoneum, were implanted, to record Thy and Tb respectively. After three days of baseline recordings of S-W, Thy and Tb at Ta of 26 dergrees C, the rats were exposed to mild cold Ta (18 degrees C) for 28 days. All the parameters were recorded during cold exposure and also for five days after the termination of cold exposure. On the first day of cold exposure there was a decrease in slow wave sleep and paradoxical sleep, but they were restored by the 21st day of continued exposure. The Thy remained decreased throughout the cold exposure. Though the Tb showed a slight decrease on the first day of cold exposure, there was no appreciable change during the subsequent days. The Thy came back to near pre exposure level on termination of cod exposure. The decrease in Thy during mild cold exposure would have triggered cold defense mechanisms. Increase in wakefulness during acute cold exposure and non-shivering thermogenesis during chronic cold exposure are probably responsible for the maintenance of Tb. Decrease in Thy is probably the key trigger for initiating thermoregulatory measures to maintain Tb and homeostatic restoration of sleep.

Basal forebrain thermoregulatory mechanism modulates auto-regulated sleep

Regulation of body temperature and sleep are two physiological mechanisms that are vital for our survival. Interestingly neural structures implicated in both these functions are common. These areas include the medial preoptic area (POA), the lateral POA, the ventrolateral POA, the median preoptic nucleus, and the medial septum, which form part of the basal forebrain (BF). When given a choice, rats prefer to stay at an ambient temperature of 27°C, though the maximum sleep was observed when they were placed at 30°C. Ambient temperature around 27°C should be considered as the thermoneutral temperature for rats in all sleep studies. At this temperature the diurnal oscillations of sleep and body temperature are properly expressed. The warm sensitive neurons of the POA mediate the increase in sleep at 30°C. Promotion of sleep during the rise in ambient temperature from 27 to 30°C, serve a thermoregulatory function. Autonomous thermoregulatory changes in core body temperature and skin temperature could act as an input signal to modulate neuronal activity in sleep-promoting brain areas. The studies presented here show that the neurons of the BF play a key role in regulating sleep. BF thermoregulatory system is a part of the global homeostatic sleep regulatory mechanism, which is auto-regulated.

Warm sensitive neurons of the preoptic area regulate ambient temperature related changes in sleep in the rat

Warm sensitive neurons (WSN) play a major role not only in body temperature regulation, but also in sleep regulation. The present study was undertaken to investigate the role of WSN of the preoptic area (POA) in mediating the ambient temperature (T(amb)) related changes in sleep. The effect of T(amb) changes on sleep and body temperature was studied in rats before and after destruction of WSN of the POA by local intracerebral injection of capsaicin. Though the rats preferred 27 degrees C T(amb), they slept maximum at 30 degrees C. After destruction of WSN of the POA, slow wave sleep (SWS) peak was brought down to 27 degrees C, which was the preferred T(amb) of the rats. This indicates that WSN of the POA mediate the increase in SWS, at temperatures higher than preferred T(amb). On the other hand, in WSN destroyed rats, rapid eye movement (REM) sleep was maximum at 33 degrees C. It suggests that the REM sleep generation is under inhibitory control of the WSN of the POA. The study supports several earlier reports that the neurons of the POA play a key role in coordinating sleep and body temperature regulation.

Glycine enhances glutamate-induced excitation in ventromedial hypothalamic neurons in awake rats

The finding that glycine potentiates N-methyl-D-aspartate (NMDA) receptor-mediated responses, has tremendously changed our understanding of glutamatergic synaptic transmission in the brain. Although the phenomenon has been confirmed in number of preparations, it is yet to be demonstrated in awake animals. Further, the controversy that glycine binding sites of NMDA receptor are saturated in vivo or not, can be best verified in awake animals. Here, we have demonstrated that glycine enhanced glutamate-induced neuronal discharges in the ventromedial nucleus of the hypothalamus of awake behaving rats using microiontophoresis technique, suggesting that the glycine binding sites of NMDA receptor are not saturated under physiological conditions.

Lysine and arginine reduce the effects of cerebral ischemic insults and inhibit glutamate-induced neuronal activity in rats

Intravenous administration of arginine was shown to be protective against cerebral ischemic insults via nitric oxide production and possibly via additional mechanisms. The present study aimed at evaluating the neuroprotective effects of oral administration of lysine (a basic amino acid), arginine, and their combination on ischemic insults (cerebral edema and infarction) and hemispheric brain swelling induced by transient middle cerebral artery occlusion/reperfusion in rats. Magnetic resonance imaging and 2,3,5-triphenyltetrazolium chloride staining were performed 2 days after ischemia induction. In control animals, the major edematous areas were observed in the cerebral cortex and striatum. The volumes associated with cortical edema were significantly reduced by lysine (2.0 g/kg), arginine (0.6 g/kg), or their combined administration (0.6 g/kg each). Protective effects of these amino acids on infarction were comparable to the inhibitory effects on edema formation. Interestingly, these amino acids, even at low dose (0.6 g/kg), were effective to reduce hemispheric brain swelling. Additionally, the effects of in vivo microiontophoretic (juxtaneuronal) applications of these amino acids on glutamate-evoked neuronal activity in the ventromedial hypothalamus were investigated in awake rats. Glutamate-induced neuronal activity was robustly inhibited by microiontophoretic applications of lysine or arginine onto neuronal membranes. Taken together, our results demonstrate the neuroprotective effects of oral ingestion of lysine and arginine against ischemic insults (cerebral edema and infarction), especially in the cerebral cortex, and suggest that suppression of glutamate-induced neuronal activity might be the primary mechanism associated with these neuroprotective effects.

Homosexuality: a dilemma in discourse!

Homosexuality has been in practice even prior to its recorded history. In the Indian cultural context, discourse on sexuality had never gained an agreeable consensus from any platform. However, in the recent past, efforts were made by governmental and nongovernmental organizations to bring sex-related issues to the masses after speculation on presumably the fast spread of AIDS (acquired immuno-deficiency syndrome) particularly through illegal homosexual activities. Nevertheless, strong cultural and religious ideologies discouraged any valid discussions on homosexuality. In light of the given scenario, the present essay aimed to highlight several aspects of homosexuality that include a brief history, biological basis, effect of nature versus nurture, evolutionary perspective and related issues concerning general well-being and health.

Activation of the gut-brain axis by dietary glutamate and physiologic significance in energy homeostasis

l-Glutamate is a multifunctional amino acid involved in taste perception, intermediary metabolism, and excitatory neurotransmission. In addition, recent studies have uncovered new roles for l-glutamate in gut-brain axis activation and energy homeostasis. l-Glutamate receptors and their cellular transduction molecules have recently been identified in gut epithelial cells. Stimulation of such l-glutamate receptors by luminal l-glutamate activates vagal afferent nerve fibers and then parts of the brain that are targeted directly or indirectly by these vagal inputs. Notably, 3 areas of the brain-the medial preoptic area, the hypothalamic dorsomedial nucleus, and the habenular nucleus-are activated by intragastric l-glutamate but not by glucose or sodium chloride. Furthermore, the chronic, ad libitum ingestion of a palatable solution of monosodium l-glutamate (1% wt:vol) by rats has also been found to reduce weight gain, fat deposition, and plasma leptin concentrations compared with rats that ingest water alone. No difference in food intake was observed. Such effects may also be vagally mediated. Together, such findings contribute to the growing knowledge base that indicates that l-glutamate signaling via taste and gut l-glutamate receptors may influence multiple physiologic functions, such as thermoregulation and energy homeostasis.

Changes in hypothalamic and body temperatures during 24 hours in rats

The available information on simultaneous assessment of body and hypothalamic temperatures in rats are lacking. In the present study these temperatures were recorded for 24 h, on three alternate days, in rats maintained at an ambient temperature of 26 +/- 1 degrees C. Hypothalamic temperature was significantly higher than body temperature during the night. In nocturnal rats the magnitude of circadian variation in hypothalamic temperature was higher than body temperature. Though maintained at different levels, both the temperatures showed closely associated diurnal changes throughout the 24 h period.

Perirhinal cortex lesions delay ejaculation in rats

Afferents from the perirhinal cortex (PRh) form a major input to the hippocampal formation, which is known to be involved in sexual behavior in rodents. But there is a lacuna in literature regarding the role of the PRh in sexual behavior. Bilateral neurotoxic lesions of the PRh delayed the ejaculation latency and prolonged the mean inter-intromission interval significantly, suggesting a facilitatory role of the PRh in male rat sex behavior.

The medial septum acts through the medial preoptic area for thermoregulation and works with it for sleep regulation

The chronic changes in sleep-wakefulness (S-W), body temperature (Tb), locomotor activity (LMA) and thermal preference were studied in male Wistar rats after the destruction of neurons in both the medial preoptic area (mPOA) and the medial septum (MS) by intracerebral injection of N-methyl-D-aspartic acid. An increase in the Tb, and a preference for higher ambient temperature (Tamb) of 30 degrees C were observed after the combined lesion of the mPOA and the MS. Similar changes were reported to occur after the lesion that was restricted to the mPOA. But these alterations were in contrast to the decrease in Tb and preference for lower Tamb, observed after the MS lesion. The thermostat of the brain would have been reset at a higher level after the combined lesion, as there was an increase in Tb, along with a preference for a higher Tamb, and an increase in LMA. There was a reduction in the frequency and the duration of the slow wave sleep (SWS) episodes, and a reduction in the frequency of the paradoxical sleep (PS) episodes after the combined lesion. The destruction of the MS neurons was probably responsible for the reduction in the frequency of SWS, whereas the loss of mPOA neurons was responsible for the decrease in the duration of SWS and frequency of PS. It can be suggested that the MS exerts its influence on thermoregulation through the mPOA. However, the MS and the mPOA seem to play independent, but complementary roles in sleep promotion.

Understanding safety of glutamate in food and brain

Glutamate is ubiquitous in nature and is present in all living organisms. It is the principal excitatory neurotransmitter in central nervous system. Glutamate is being used as food additive for enhancing flavour for over last 1200 years imparting a unique taste known as "umami" in Japanese. It is being marketed for about last 100 years. The taste of umami is now recognized as the fifth basic taste. Many of the foods used in cooking for enhancing flavour contain high amount of glutamate. Breast milk has the highest concentration of glutamate amongst all amino acids. Glutamate in high doses as gavage or parenteral injection have been reported to produce neurodegeneration in infant rodents. The neurodegeneration was not produced when gluamate was given with food. The Joint FAO/WHO Expert Committee on Food Additives, based on enumerable scientific evidence, has declared that, "glutamate as an additive in food" is not an health hazard to human being. Glutamate is used as signaling molecule not only in neuronal but also in non-neuronal tissues. Excessive accumulation of glutamate in the synaptic cleft has been associated with excitotoxicty and glutamate is implicated in number of neurological disorders. Excessive accumulation could be attributed to increase release, failure of transport system for uptake mechanism, neuronal injury due to hypoxia-ischemia, trauma and associated metabolic failures. The role blood brain barrier, vesicular glutamate and sodium dependent excitatory amino acid transporters in glutamate homeostasis are emphasized in the review.

Noradrenergic afferents and receptors in the medial preoptic area: neuroanatomical and neurochemical links between the regulation of sleep and body temperature

Several studies have shown the importance of the medial preoptic area in the regulation of sleep-wakefulness and of body temperature. The medial preoptic area has a rich noradrenergic innervation, coming mostly from the lateral tegmental noradrenergic system. The accumulating evidences show that the noradrenergic afferents to the medial preoptic area are involved in the induction of sleep. This hypnogenic mechanism operates through the postsynaptic alpha1 and alpha2-adrenergic receptors. Noradrenergic afferents are also involved in the thermoregulatory mechanisms, and the activation of these fibers brings about a fall in body temperature. Though the body temperature changes are brought about by the same receptor subtypes as those involved in hypnogenesis, observations suggest the possibility of separate sets of noradrenergic afferents in the medial preoptic area for sleep regulation and thermoregulation. In this review, we present the compelling evidences, which showed that the noradrenergic afferents of the medial preoptic area bring about a fall in body temperature and other thermoregulatory behavioral alterations associated with sleep.

Brain areas activated after ejaculation in healthy young human subjects

Brain mechanisms for the refractory period that characteristically follows ejaculation in animals and human are poorly understood. The possibility of active inhibition of brain areas being responsible for the post-ejaculatory inhibitory state has not been ruled out. Using Blood Oxygen Level Dependent (BOLD) functional magnetic resonance imaging (fMRI) we have mapped brain areas in healthy young volunteers immediately after ejaculation. Functional imaging of the brain for 30 minutes beginning after three minutes of ejaculation induced by masturbation showed spatio-temporal activation in amygdala, temporal lobes and septal areas. The septal areas were observed to be active for a shorter duration than the amygdala and the temporal lobe. Thus the temporal sequence of involvement of the above neural structures may contribute to temporary inhibition of sexual arousal/penile erection during the post-ejaculatory refractory period in humans.

Alpha-1 adrenergic receptors in the medial preoptic area are involved in the induction of sleep

This paper reviews the recent studies that led to the conclusion that the noradrenergic neurons projecting to the medial preoptic area (mPOA) are hypnogenic and that they mediate this action through alpha(1) adrenergic receptors. Microinjection of noradrenaline (NA) into the mPOA induced arousal. Studies using alpha(2) adrenergic drugs showed that the arousal induced by intrapreoptic injection of NA was due to its action on presynaptic alpha(2) adrenergic receptors. A combination of lesion and chemical stimulation techniques demonstrated that when NA acted on the postsynaptic alpha(1 )receptors in the mPOA, it induced sleep. Intrapreoptic injection of alpha(1) agonist, methoxamine could induce sleep, when the hypothermia, which was simultaneously produced, was behaviorally compensated for by the animal. Increased arousal produced by the destruction of noradrenergic fibers in the mPOA further confirmed the hypnogenic role of these fibers.

Sleep induction and temperature lowering by medial preoptic α1 adrenergic receptors

Changes in sleep-wakefulness (S-W) and body temperature (T(b)) on administration of alpha(1) agonist (methoxamine) and antagonist (prazosin) into the medial preoptic area (mPOA) were studied in rats. Presynaptic catecholaminergic terminals of the mPOA were destroyed by injecting 6-hydroxydopamine at the ventral noradrenergic bundle (VNA), before administration of the drugs. Microinjection of 0.05 microg methoxamine induced sleep, though 0.1 microg prazosin produced no change in S-W. On the other hand, in normal rats, the same dose of methoxamine produced no change, while prazosin produced arousal. Denervation hypersensitivity may be responsible for the appearance of hypnogenic response on methoxamine administration, in the VNA-lesioned rats. The VNA-lesioned animals (before administration of any drug) had higher pre-injection values of wake period than the normal rats. A reduction in the tonic activity of noradrenergic fibers to the mPOA, and resulting reduced activity of alpha(1) receptors, may be responsible for increased wake period in the VNA-lesioned rats. The action of prazosin was probably abolished in the absence of tonic activity of alpha(1) receptor in the VNA-lesioned rats. Reduction and increase in T(b) produced by methoxamine and prazosin, respectively, confirm the involvement of alpha(1) receptors in the thermal changes. Methoxamine was less effective, than in normal rats, in reducing T(b). So, the possibility of involvement of presynaptic receptors in the thermal response is suggested. The results suggest the involvement of separate sets of alpha(1) receptors (and neurons) in hypnogenesis and in lowering T(b). As sleep is associated with fall in T(b), the alpha(1) adrenergic receptors may be involved in interlinking sleep regulation and thermoregulation.

Tonic activity of alpha1 adrenergic receptors of the medial preoptic area contributes towards increased sleep in rats

Several studies have suggested that noradrenergic afferents to the medial preoptic area might be involved in hypnogenesis and in lowering the body temperature, and that the alpha1 adrenergic receptors might be mediating these responses. This study was undertaken to find out the changes in sleep-wakefulness and body temperature in rats, when these adrenergic receptors of the medial preoptic area are blocked by alpha1 selective antagonist, prazosin. Adult male Wistar rats were chronically implanted with electrooculogram, electroencephalogram and electromyogram electrodes for sleep-wakefulness assessment, and a bilateral guide cannula for microinjection of prazosin at the medial preoptic area. A radio-transmitter was implanted in the abdomen for telemetric measurement of body temperature in four groups of rats. Sleep-wakefulness was also assessed telemetrically in four other groups of rats. Sleep-wakefulness recordings from these rats were done in a specialized chamber, where they could move about freely and select the ambient temperature which they prefer. Prazosin induced a dose dependent increase in wake period and in body temperature, when microinjected into the medial preoptic area. Results suggest that preoptic alpha1 adrenergic receptors mediate hypnogenic and hypothermic responses. It is proposed that the noradrenergic afferents to the medial preoptic area, by tonic activation of alpha1 adrenergic receptors, contribute towards increase in sleep especially during the daytime.

Ambient temperature related sleep changes in rats neonatally treated with capsaicin

Ambient temperature related sleep changes in rats neonatally treated with capsaicin. PHYSIOL BEHAV 00(0) 000-000, 2004. The study was conducted on adult male Wistar rats, neonatally treated with capsaicin to destroy the peripheral warm receptors. The sleep-wakefulness was recorded for 5 h at an ambient temperature (T(amb)) of 18, 24, 30 and 33 degrees C on different days. The rectal temperatures (T(r)) of the rats were studied on exposure to 6 and 37 degrees C for 2 h to assess their thermoregulatory ability. The changes in the behavioral thermoregulation were assessed by noting the thermal preference of rats when they were placed in an environmental chamber with 3 interconnected compartments maintained at 24, 27 and 30 degrees C. Slow wave (SWS) and rapid eye movement (REM) sleep were decreased at 18 degrees C and increased at 30 degrees C, in control rats. There was a decrease in REM sleep and no change in SWS when T(amb) was raised from 30 to 33 degrees C. However, in neonatally capsaicin treated rats, sleep was increased even at 33 degrees C, though there was no significant change in sleep when T(amb) was increased from 18 to 24 degrees C. Capsaicin treated rats showed thermoregulatory deficiency at 37 degrees C but the thermal preference was unaltered in these rats. The results suggest that the central warm receptors can produce alteration in sleep at different T(amb), even in absence of peripheral warm receptors. The behavioral thermoregulation was unaffected in these rats, though their ability to defend the body temperature in warm environment was affected.

Differences in the effects of medial and lateral preoptic lesions on thermoregulation and sleep in rats

The effects of the destruction of the medial preoptic area and the lateral preoptic area with N-methyl-d-aspartic acid on sleep-wakefulness, brain temperature and thermoregulation were studied in two groups of male Wistar rats. Electroencephalogram, electrooculogram and electromyogram, along with brain temperature, were recorded for 3 days, prior to the destruction of the medial preoptic area and the lateral preoptic area, and on the 7th and 21st days after the destruction of these areas. The thermoregulatory capacity of the rats was assessed by recording their brain temperature when they were exposed to severe cold (5+/-1 degrees C) and heat (37+/-1 degrees C) before and after the lesion. Though sleep was decreased after the destruction of both the medial preoptic area and the lateral preoptic area, paradoxical sleep was reduced only by the destruction of the medial preoptic area. Decrease in sleep after the medial preoptic area lesion was brought about by a decrease in the duration of the slow wave sleep episodes and the frequency of paradoxical sleep episodes. Decrease in sleep after the lateral preoptic area lesion was brought about by a decrease in the frequency of slow wave sleep episodes. There was a significant increase in brain temperature after the medial preoptic area lesion but not after the lateral preoptic area lesion. The rats with lesion in the medial preoptic area showed deficits in thermoregulation on exposure to cold, while those with the lateral preoptic area lesion showed deficits in heat defense ability. The present findings suggest that the medial preoptic area and the lateral preoptic area regulate sleep by different modalities and that there is an anatomical segregation of heat and cold defense functions within the basal forebrain.

The changes in thermal preference, sleep–wakefulness, body temperature and locomotor activity in the rats with medial septal lesion

The effects of the destruction of the medial septal neurons (MS) with N-methyl-d-aspartic acid on sleep-wakefulness (S-W), body temperature (Tb), locomotor activity (LMA) and thermal preference were studied in male Wistar rats. When these rats were given a choice of three ambient temperatures (Tamb) of 24, 27 and 30 degrees C, they preferred 27 degrees C before the lesion. But they chose 30 degrees C during the initial days and 24 degrees C by the third week after the MS lesion. The MS lesion produced an increase in paradoxical sleep (PS) though this change was not very evident when the rats were not allowed to choose their Tamb. Though there was a decrease in slow wave sleep (SWS), it recovered considerably, when the lesioned rats chose their preferred Tamb. However, the frequency of SWS episodes did not show any recovery. There was a decrease in both Tb and LMA by the third week after the MS lesion. It can, therefore, be concluded that the MS lesion affected the initiation of SWS, as there was a decrease in the frequency of SWS episodes. Study of S-W in the rats that were given freedom to select Tamb helped to demonstrate the role of the MS in the inhibition of PS. It also showed that the thermostat of the rats was reset at a lower level by the third week after the MS lesion. Decrease in heat production resulting from a decrease in LMA, could have contributed towards the animals' efforts to maintain a lower Tb.

Sleep changes during chronic cold exposure showed that the homeostatic requirement of sleep is reduced in the medial preoptic area lesioned rats

The effects of chronic exposure to a mildly cold ambient temperature (T(a)) of 18 degrees C on sleep wakefulness (S-W) and brain temperature (T(br)) were studied in the medial preoptic area (mPOA) lesioned male Wistar rats. Electroencephalogram (EEG), electrooculogram (EOG) and electromyogram (EMG) electrodes were chronically implanted to assess S-W, and a thermocouple above the dura to record the T(br). After three recordings (24 h each) of S-W and T(br) at 24 degrees C, N-methyl D-aspartic acid (NMDA) was intracerebrally injected to produce bilateral destruction of neurons in the mPOA. There was decreased sleep and increased T(br) even four weeks after the mPOA lesion. T(a) of the environmental chamber was then reduced to 18 degrees C, and the S-W and T(br) were again recorded for 24 h each on the 1st, 7th, 14th, 21st, and on 28th days of continuous exposure to the mild cold T(a). Exposure to the cold produced further decrease in sleep and increase in the T(br). However, sleep came back to the pre-exposure level by the 14th day. An increase in the duration of sleep episodes was responsible for the restoration of sleep during chronic cold exposure. The study showed that the requirement of sleep was reset at a lower level in the mPOA lesioned rats. The mPOA lesion affected the sleep maintenance and sleep initiation, though the latter became evident only during chronic cold exposure. The magnitude of the acute changes in T(br) and S-W were less in the lesioned rats, as compared to those observed in the normal rats exposed to similar cold T(a). On the basis of these observations, it could be proposed that the mPOA plays some role in cold induced changes in thermoregulation and sleep regulation. The T(br) remained elevated throughout the period of cold exposure. Resetting of the T(br), at a higher level may be part of the homeostatic readjustment to restore sleep.

Unmasking of alpha1 adrenoceptor induced hypnogenic response from medial preoptic area

Earlier studies had indicated the possibility of the involvement of the alpha(1) adrenergic receptors on the medial preoptic (mPOA) neurons in hypnogenesis. Microinjection of alpha1 agonist methoxamine (0.05 microg) into the mPOA of the rats, maintained at an ambient temperature (Tamb) of 24 degrees C, did not produce any significant change in sleep-wakefulness (S-W), except for an arousal of short duration, which coincided with the steep fall in body temperature (Tb). It was probably not possible to elicit sleep, because of hypothermia simultaneously produced by this drug. To test this hypothesis, experiments were conducted in an environment where the effects of hypothermia could be partially compensated for. When the rats were allowed to select their Tamb, they moved over to a compartment having a higher Tamb of 30 degrees C, on administration of methoxamine into the mPOA. Simultaneously, there was induction of sleep, which lasted for 60 min. Thus, it was possible to demonstrate the hypnogenic action of methoxamine, which was masked by hypothermic action of the drug. The findings indicate that the alpha1 adrenergic receptors in the mPOA are involved in the induction of sleep.

Changes in brain temperature and thermoregulation produced by destruction of medial septal neurons in rats

Brain temperatures (Tbr) of male Wistar rats were recorded at every 15 min interval for 24 h, prior to the destruction of the medial septal (MS) neurons with N-methyl-D-aspartic acid, and on the 7th, 14th and 21st days after the destruction. The capacity of the rats to regulate their body temperature under severe cold and heat was assessed by recording their Tbr when they were exposed to 5+/-1 and 37+/-1 degrees C for 2 h, before lesion and on 8th, 9th, 15th, 16th, 22nd and 23rd days after the lesion. The Tbr was decreased and its circadian variation increased after the MS lesion. On exposure to an ambient temperature of 5+/-1 degrees C the Tbr was decreased on 9th and 16th days after the lesion, when compared with the sham lesion group on identical days, though the fall in temperature was not significant on the 23rd day. The change in Tbr (compared with the sham lesion group) was not significantly different on all days of exposure to 37+/-1 degrees C. The decrease in Tbr after the MS lesion is in contrast to the hyperthermia produced by lesion of the adjoining thermoregulatory areas. The present findings suggest that the MS lesions caused an alteration in the set point of body temperature, without drastic changes in thermoregulatory ability.

Gating of the dorsal penile nerve inputs by norepinephrine at the medial preoptic area in rats

The medial preoptic area neurons related to male sexual behaviour in rats were identified by their responses to dorsal penile nerve stimulation. These neurons were further tested with norepinephrine applied iontophoretically. From the 21 medial preoptic area neurons recorded in urethane anaesthetized rats, 17 neurons responded to dorsal penile nerve stimulation. Excitatory and inhibitory responses were found in almost equal number of neurons. 14 neurons responded to norepinephrine application, out of which six neurons were excited and eight were inhibited. The direction of changes produced by dorsal penile nerve stimulation and norepinephrine application were similar in 10 neurons. The results suggest that the sensory inputs from the genitalia are possibly gated by norepinephrine at the level of the medial preoptic area. Afferent information from the genitalia carried by dorsal penile nerve and the availability of norepinephrine at the level of the medial preoptic area probably help in maintaining adequate level of sexual arousal.

Changes in sleep on chronic exposure to warm and cold ambient temperatures

Alterations in sleep induced by chronic exposure to mild changes in ambient temperature (Ta) were studied in male Wistar rats with chronically implanted electrodes for recording electrooculogram (EOG), electroencephalogram (EEG) and electromyogram (EMG), and a thermocouple to record the brain temperature (Tbr). Changes in sleep-wakefulness (S-W) and Tbr on exposure to warm (30+/-1 degrees C) and cold (18+/-1 degrees C) Ta for 4 weeks were studied in two groups of five rats each. Chronic heat exposure produced a persistent increase in sleep, primarily due to an increase in the durations of sleep episodes. A disproportionate increase in sleep during the dark period resulted in reduced circadian variation. The paradoxical sleep (PS)/total sleep time (TST) ratio also remained increased, during heat exposure. On chronic cold exposure, the sleep was decreased initially, but it recovered after 3 weeks, due to an increase in the frequency of slow wave sleep (SWS) episodes. The Tbr was not altered on exposure to warm Ta, but it remained high throughout the 4 weeks of cold exposure. The increase in the amount of sleep, especially the PS with enhanced ambient temperature, may be considered as an adaptation to thermal load aimed at energy conservation. Though the increased wakefulness is suggested to enable the organism to optimize thermoregulation during acute cold stress, thermoregulation itself may be readjusted to ensure homeostatic restoration of sleep during chronic cold exposure.

Functional MRI shows activation of the medial preoptic area during sleep

Changes in the activity of the basal forebrain sleep regulating areas were studied noninvasively in conscious rats by employing functional magnetic resonance imaging (fMRI). Sleep-wakefulness (S-W) stages were identified with the help of electrophysiological recordings carried out simultaneously. An increase in the signal intensity was observed in the medial preoptic area (mPOA) during sleep indicating a heightened activity of neurons in this area. In some rats, there was a decrease in the activity of the fronto-parietal cortex. The sleep-induced increase in activity in the mPOA and decrease in the fronto-parietal cortex are in relation to their levels in the awake state. The findings helped to localize the critical area for the maintenance of slow wave sleep at the mPOA. These results further corroborate some of the previous suggestions based on neurotoxic lesion, chemical stimulation and electrophysiological recordings.

Changes in sleep-wakefulness in the medial preoptic area lesioned rats: role of thermal preference

Changes in sleep-wakefulness (S-W) were studied in adult male Wistar rats, along with body temperature (T(b)), locomotor activity (LMA) and thermal preference, after the lesion of the medial preoptic area (mPOA) with N-methyl-D-aspartic acid (NMDA). The sleep was decreased after the lesion of the mPOA, but there was recovery when the rats were given freedom to stay in an ambient temperature (T(amb)) which they preferred. When given a choice between three T(amb) (24, 27 and 30 degrees C), the rats preferred 27 degrees C before the mPOA lesion, and 24 degrees C during the initial days after the lesion. There was a shift in the thermal preference to 30 degrees C, on the fourth week after the lesion, which coincided with the considerable recovery of sleep. The preference for higher T(amb) probably helped to improve sleep, as T(amb) of 30 degrees C is known to promote sleep. When the lesioned rats were not given the freedom to select the T(amb), there was no recovery in sleep. The mPOA seems to be essential for increasing the durations of slow wave sleep (SWS) episodes, especially the light SWS (S1), as they remained shorter than the pre-lesion value, even when the rats were given freedom to stay in a preferred T(amb). The homeostatic recovery of sleep, especially the night time sleep, resulted in the disruption of circadian sleep rhythm. But, the LMA, T(b) and thermal preference maintained their diurnal variation. T(b) and LMA were elevated after the mPOA lesion and they remained so till the end of the study.

Atenolol or butoxamine injection at the lateral septum doesn't inhibit male sexual behavior in rats

To investigate the role of specific adrenoreceptors subtypes on sexual behavior, atenolol, butoxamine, a mixture of atenolol and butoxamine, and saline (vehicle) were injected into the lateral septum in four different groups of sexually active male rats. Application of a mixture of atenolol and butoxamine produced inhibition of copulatory activity. On the other hand, application of either atenolol or butoxamine alone did not inhibit copulatory activity. But it produced stimulation of some of the components of male sexual behavior. Inability of either atenolol or butoxamine to inhibit the male sexual behavior, and inhibition of the same by the mixture of atenolol and butoxamine, indicate that both beta-adrenoreceptors at the lateral septum are involved in the elaboration of male sexual behavior. Stimulation of some components of sexual behavior on application of atenolol or butoxamine could be attributed to an unbalanced activity of beta-adrenoreceptors.

Sleep-related penile erections do not occur in rats during carbachol-induced rapid eye movement sleep

This study was undertaken to find out whether sleep-related penile erections occur in the carbachol-induced rapid eye movement sleep model in rats. Bulbospongiosus EMG, as a measure of penile erection, was recorded along with EEG, EMG, and EOG during normal sleep-wakefulness. These parameters were again recorded after injection of carbachol into the pontine tegmentum. Carbachol-induced rapid eye movement sleep was not accompanied by penile erections.

Sleep changes produced by destruction of medial septal neurons in rats

Changes in sleep-wakefulness were studied in male Wistar rats after destruction of the medial septal neurons with NMDA. Electroencephalogram, electromyogram and electrooculogram were recorded for 24 h prior to the destruction of the medial septum, and 7, 14 and 21 days after the destruction. There was a decrease in the total amount of slow wave sleep and frequency of slow wave sleep episodes after the lesion. It also produced an increase in the duration of paradoxical sleep episodes. These findings are in contrast to the changes produced after lesion of other basal forebrain areas. The present findings suggest that the medial septum may be involved in the genesis of slow wave sleep and inhibition of the durations of paradoxical sleep episodes.

Changes in thermal preference, sleep–wakefulness, body temperature and locomotor activity of rats during continuous recording for 24 hours

This study was aimed at correlating diurnal changes in thermal preference of rats with their body temperature (Tb), sleep-wakefulness (S-W) and locomotor activity (LMA). Electroencephalogram (EEG), electromyogram (EMG), electrooculogram (EOG) and Tb were recorded by telemetry, while an activity monitor measured LMA and thermal preference. A special environmental chamber, which was designed and fabricated, enabled for the first time, simultaneous measurement of thermal preference, along with S-W and Tb. S-W, thermal preference and LMA were recorded continuously in six adult male Wistar rats, for 24 h, for 3 days, and Tb with thermal preference and LMA were recorded for another 3 days. LMA and Tb were higher at night than during day. The rats slept less during the night time. Increased frequency of sleep episodes contributed towards increased sleep during day time. They preferred an ambient temperature (Tamb) of 24 degrees C at night and 27 degrees C during the day. Though the preference for higher Tamb during day time coincided with increased sleep, the rats did not move over to higher Tamb prior to the onset of sleep episodes. Though the diurnal alterations in sleep, Tb and LMA were similar to those reports from animals kept in constant Tamb, the day-night variation of paradoxical sleep (PS) was exaggerated when the rats selected their own preferred Tamb.

Repeated intracerebral microinjections: efficacy in studying brain functions

Injection of chemicals into the brain has been considered as an important technique to study various functions of the brain. In these studies, as a rule, only one bilateral injection is given in one animal. This study was undertaken to evaluate the quality of the body temperature data obtained after first and second injections of methoxamine and artificial cerebrospinal fluid into the medial preoptic area. Though there was quantitative decrease in the effects produced after the second injection of the drug, there was no significant change in the effects produced by the second injections of artificial cerebrospinal fluid, which was used as a vehicle. Results of this study support the earlier recommendation to perform only one injection in any of the brain sites for evaluating the effect of any drug. But the vehicle can be administered as a second injection, without compromising on the quality of data.

Free glutamic acid content of milk in Indian mothers

Free amino acids levels in the milk of 11 healthy Indian mothers were determined using automatic precolumn derivatization procedure. The aim of the study was to find out the relative concentration of glutamic acid and glutamine in the milk. Glutamic acid is the dominant free amino acid found in the milk of Indian mothers. Glutamic acid and glutamine together formed the major nonessential amino acids present in the human milk. Although glutamic acid has been shown to be the major amino acid in human milk in many studies, to the best our knowledge, this is the first report to confirm that glutamic acid is the most abundant amino acid in milk in Indian mothers.

Changes in body temperature and sleep-wakefulness after intrapreoptic injection of methoxamine in rats

Several pieces of evidence suggest that the noradrenergic afferents in the medial preoptic area produce sleep and hypothermia by acting on alphal adrenergic receptors. On the other hand, in a few studies monitoring body temperature with a rectal probe, preoptic injection of the alphal adrenergic agonist methoxamine produced contradictory changes in body temperature and sleep-wakefulness. Such contradictions call for the re-examination of methoxamine induced body temperature changes using a better technique like telemetric recording. In the present study, we monitored body temperature and sleep-wakefulness simultaneously after the micro-injection of 0.5, 1, and 2 micromol methoxamine, into the medial preoptic area of adult male Wistar rats. Methoxamine injection produced hypothermia but no major change in sleep-wakefulness during the 3 hours after drug injection, except for a short period (15 min) of sleep after 120 min of injection. A short period of wakefulness, coinciding with the maximum fall in body temperature (30 min after injection) occurred when methoxamine was administered at higher doses. The results of this study indicate that alphal adrenergic receptors participate in preoptically mediated thermoregulatory measures that reduce body temperature. Hypothermia induced by methoxamine might have masked the hypnogenic action of this drug.

Orexin A (hypocretin-1) application at the medial preoptic area potentiates male sexual behavior in rats

The medial preoptic area plays an important role in the regulation of male sexual behavior in rats, and this area receives orexinergic inputs. The role of orexinergic inputs in the medial preoptic area in sexual behavior has not been studied, though they have been shown to play a role in some other physiological functions. In this study, the changes in male sexual behavior in rats were studied after local injection of orexin A (Hypocretin-1) at the medial preoptic area. The results of the study showed that orexin A application at the medial preoptic area increased sexual arousal as well as the copulatory performance. Sexual arousal is one of the physiological stimuli, which influences wakefulness. It is possible that the earlier reports showing increased wakefulness, on application of orexin A at the medial preoptic area/basal forebrain, has a contribution from sexual arousal.