Birendra Nath Mallick

Different types of norepinephrinergic receptors are involved in preoptic area mediated independent modulation of sleep-wakefulness and body temperature

The preoptic area is known to regulate sleep-wakefulness and body temperature. It was suggested earlier that though sleep-wakefulness and body temperature may affect each other, the preoptic area mediated influence on those two physiological phenomena is likely to be independent of alteration in each other. Since intrapreoptic area norepinephrine could modulate both those functions, study of that system was undertaken. It was hypothesized that since the preoptic area has different types of norepinephrinergic receptors (viz. alpha 1, alpha 2 and beta), independent modulation of those two functions was probably due to activation or inactivation of separate receptors. Hence, the effects of different agonist and antagonist of those receptors individually as well as in combination into the preoptic area were studied on those two functions in freely moving rats. The results suggest that norepinephrine induced preoptic area mediated influence on the body temperature is primarily regulated by the alpha 1 receptors while the sleep and wakefulness are regulated by alpha 2 and beta receptors, respectively. The finding should help in explaining several poorly understood observations reported earlier and it suggests that similar phenomena may possibly exist in other system involving other neurotransmitters as well.

Mild electrical stimulation of pontine tegmentum around locus coeruleus reduces rapid eye movement sleep in rats

The norepinephrinergic neurons in the locus coeruleus (LC) cease firing during REM sleep (REMS) and increase firing during REMS deprivation. Most of the earlier studies used lesion and transection techniques which could not confirm the role of LC in REMS generation and/or its maintenance, if at all. Hence, in this study it was hypothesized that if the LC REM-off neurons must cease firing before the onset of REMS, its continuous activation should eliminate or at least reduce REMS. Electrophysiological parameters characterizing sleep-wakefulness-REMS were recorded in freely moving male albino rats. In an attempt not to allow the REM-off LC neurons to cease firing, low intensity (200 microA), low frequency (2 Hz) rectangular (300 microseconds) pulses were continuously delivered to the LC bilaterally through chronically implanted electrodes, and the effects on sleep-wakefulness-REMS were investigated. Although the stimulation did not affect sleep state of the animals, it reduced REMS significantly. The effect on REMS was similar to that of REMS deprivation. Total duration of REMS was significantly reduced during stimulation and showed a rebound increase during the post stimulation period. This reduction in REMS duration was primarily due to a significant reduction in the REMS frequency/h while the mean REMS duration/episode was not affected. Thus, the results of this study suggest that the stimulated area (LC) affects REMS, most likely by suppression of REMS generation process.

Norepinephrine-Stimulated Increase in Na+,K+-ATPase Activity in the Rat Brain Is Mediated Through α1A-Adrenoceptor Possibly by Dephosphorylation of the Enzyme

Abstract: Rapid eye movement sleep deprivation is reported to increase Na+,K+‐ATPase activity. This increase was shown earlier to be stimulated by norepinephrine acting on α1‐adrenoceptor. The involvement of a subtype of α1‐adrenoceptor and the possible molecular mechanism of action of norepinephrine in increasing the enzyme activity were investigated using receptor agonists and antagonists, as well as stimulants and blockers of signal transduction pathway. It was observed that incubation of the homogenate with cyclic AMP, forskolin, A23187 (a calcium ionophore), or calmodulin alone did not stimulate the Na+,K+‐ATPase activity. However, although the spontaneous activity of the Na+,K+‐ATPase was not affected by prazosin, WB4101, heparin, W13, or cyclosporin A alone, each of them could prevent the norepinephrine‐stimulated increase in the enzyme activity. Based on these results and our previous findings, it is proposed that norepinephrine acted on α1A‐adrenoceptor and increased intracellular calcium, which in the presence of calmodulin activated a calmodulin‐dependent phosphatase, calcineurin. This calcineurin possibly dephosphorylated Na+,K+‐ATPase and increased its activity. The physiological significance especially in relation to rapid eye movement sleep deprivation is discussed.

Role of norepinephrine in the regulation of rapid eye movement sleep.

Sleep and wakefulness are instinctive behaviours that are present across the animal species. Rapid eye movement (REM) sleep is a unique biological phenomenon expressed during sleep. It evolved about 300 million years ago and is noticed in the more evolved animal species. Although it has been objectively identified in its present characteristic form about half a century ago, the mechanics of how REM is generated, and what happens upon its loss are not known. Nevertheless, extensive research has shown that norepinephrine plays a crucial role in its regulation. The present knowledge that has been reviewed in this manuscript suggests that neurons in the brain stem are responsible for controlling this state and presence of excess norepinephrine in the brain does not allow its generation. Furthermore, REM sleep loss increases levels of norepinephrine in the brain that affects several factors including an increase in Na-K ATPase activity. It has been argued that such increased norepinephrine is ultimately responsible for REM sleep deprivation, associated disturbances in at least some of the physiological conditions leading to alteration in behavioural expression and settling into pathological conditions.

Increased apoptosis in rat brain after rapid eye movement sleep loss

Rapid eye movement (REM) sleep loss impairs several physiological, behavioral and cellular processes; however, the mechanism of action was unknown. To understand the effects of REM sleep deprivation on neuronal damage and apoptosis, studies were conducted using multiple apoptosis markers in control and experimental rat brain neurons located in areas either related to or unrelated to REM sleep regulation. Furthermore, the effects of REM sleep deprivation were also studied on neuronal cytoskeletal proteins, actin and tubulin. It was observed that after REM sleep deprivation a significantly increased number of neurons in the rat brain were positive to apoptotic markers, which however, tended to recover after the rats were allowed to undergo REM sleep; the control rats were not affected. Further, it was also observed that REM sleep deprivation decreased amounts of actin and tubulin in neurons confirming our previous reports of changes in neuronal size and shape after such deprivation. These findings suggest that one of the possible functions of REM sleep is to protect neurons from damage and apoptosis.

Differential acute influence of medial and lateral preoptic areas on sleep-wakefulness in freely moving rats.

The role of preoptic area (POA) in sleep-wakefulness and related EEG changes is well established. Anatomically the area is divided into medial (mPOA) and lateral (IPOA) portions having different physiological functions. Knowledge regarding the differential role, if any, of those two areas in sleep and wakefulness was lacking in the literature. Therefore, an attempt was made in this study, to investigate the same systematically. Experiments were conducted during day and night in freely moving rats. Electrophysiological parameters defining sleep and wakefulness were recorded before and after reversible inactivation of those two areas separately by microinjection of a local anaesthetic, marcain. The responses were opposite in nature depending upon the time, day or night, when the anaesthetic was applied. During the day, anaesthetization induced wakefulness while during the night, sleep was precipitated. However, anaesthetization of both the areas though induced similar qualitative response, the degree of the responses differed significantly. The results suggest that the mPOA is more effective in maintaining tonic sleep while the IPOA is more potent in the maintenance of tonic wakefulness in the normal rats. The finding supports and fits well with the existing knowledge.

Effect of rapid eye movement sleep deprivation on rat brain monoamine oxidases

Monoamine oxidase, monoamine oxidase-A, and monoamine oxidase-B activities were compared in free moving, rapid eye movement sleep-deprived, recovered, and control rat brains. The activities were estimated in the whole brain, cerebrum, cerebellum, whole brainstem, medulla, pons, and midbrain. The flowerpot method was used for continuing deprivation for one, two, or four days. Monoamine oxidase activity decreased significantly in the cerebrum and the cerebellum of the sleep-deprived rats, whereas monoamine oxidase-A and monoamine oxidase-B were differentially affected. Medullary MAO-A was the first to be affected, showing an increase after just one day of rapid eye movement sleep deprivation, while longer deprivation decreased its activity. The activity of monoamine oxidase-B was not significantly affected in any brain areas of the deprived rats until after two days of rapid eye movement sleep deprivation. All the altered enzyme activities returned to control levels after recovery. Control experiments suggest that the decrease was primarily caused by the rapid eye movement sleep deprivation and was not due to nonspecific effects. These findings are consistent with past studies and may help to explain earlier observations. The results support the involvement of aminergic mechanisms in rapid eye movement sleep. The plausible reasons for the changes in the activities of monoamine oxidases, after rapid eye movement sleep deprivation, are discussed.

REM sleep loss increases brain excitability: role of noradrenalin and its mechanism of action

Ever since the discovery of rapid eye movement sleep (REMS), studies have been undertaken to understand its necessity, function and mechanism of action on normal physiological processes as well as in pathological conditions. In this review, first, we briefly surveyed the literature which led us to hypothesise REMS maintains brain excitability. Thereafter, we present evidence from in vivo and in vitro studies tracing behavioural to cellular to molecular pathways showing REMS deprivation (REMSD) increases noradrenaline level in the brain, which stimulates neuronal Na-K ATPase, the key factor for maintaining neuronal excitability, the fundamental property of a neuron for executing brain functions; we also show for the first time the role of glia in maintaining ionic homeostasis in the brain. As REMSD exerts a global effect on most of the physiological processes regulated by the brain, we propose that REMS possibly serves a housekeeping function in the brain. Finally, subject to confirmation from clinical studies, based on the results reviewed here, it is being proposed that the subjects suffering from REMS loss may be effectively treated by reducing either noradrenaline level or Na-K ATPase activity in the brain.

Increased levels of tyrosine hydroxylase and glutamic acid decarboxylase in locus coeruleus neurons after rapid eye movement sleep deprivation in rats

Norepinephrine, acetylcholine and GABA levels alter during rapid eye movement (REM) sleep and its deprivation. Increased synthesis of those neurotransmitters is necessary for their sustained release. Hence, in this study, the concentrations of tyrosine hydroxylase (TH), choline acetyl transferase (ChAT) and glutamic acid decarboxylase (GAD), the enzymes responsible for their synthesis, were immunohistochemically estimated within the neurons in locus coeruleus, laterodorsal tegmentum and pedunculopontine tegmentum and medial preoptic area in REM sleep deprived and control rats. It was observed that as compared to controls, deprivation increased TH and GAD significantly in the locus coeruleus only, while in other areas, they remained unchanged. The findings help explaining the mechanism of increase in neurotransmitter levels in the brain after REM sleep deprivation and their significance has been discussed.

GABA in locus coeruleus regulates spontaneous rapid eye movement sleep by acting on GABAA receptors in freely moving rats

The aminergic neurons in the locus coeruleus are known to cease firing during rapid eye movement sleep. Since electrical stimulation of locus coeruleus reduced, while carbachol stimulation increased rapid eye movement sleep and gamma-aminobutyric acid (GABA) neurons as well as terminals are present in the locus coeruleus, we hypothesized that GABA may be involved for cessation of locus coeruleus neuronal firing during rapid eye movement sleep. Under surgical anaesthesia male Wistar rats (250-300 g) with bilateral guide cannulae targeting locus coeruleus were prepared for chronic sleep-wakefulness recording. Electroencephalogram (EEG), electrooculogram (EOG), electromyogram (EMG) were recorded in normal, after 250 nl saline and after picrotoxin (250 ng in 250 nl) injection bilaterally into the locus coeruleus. The results showed that mean duration per episode of rapid eye movement sleep was significantly reduced, although its frequency of generation/h was not significantly affected. This study suggests that GABA in locus coeruleus is involved in tonic regulation of rapid eye movement sleep and the action is mediated through GABAA receptor.