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

The Antidepressant-like Effects of Estrogen-mediated Ghrelin

Ghrelin, one of the brain-gut peptides, stimulates food-intake. Recently, ghrelin has also shown to play an important role in depression treatment. However, the mechanism of ghrelin's antidepressant-like actions is unknown. On the other hand, sex differences in depression, and the fluctuation of estrogens secretion have been proved to play a key role in depression. It has been reported that women have higher level of ghrelin expression, and ghrelin can stimulate estrogen secretion while estrogen acts as a positive feedback mechanism to up-regulate ghrelin level. Ghrelin may be a potential regulator of reproductive function, and estrogen may have additional effect in ghrelin's antidepressantlike actions. In this review, we summarize antidepressant-like effects of ghrelin and estrogen in basic and clinical studies, and provide new insight on ghrelin's effect in depression.

A study on fear memory retrieval and REM sleep in maternal separation and isolation stressed rats

As rapid brain development occurs during the neonatal period, environmental manipulation during this period may have a significant impact on sleep and memory functions. Moreover, rapid eye movement (REM) sleep plays an important role in integrating new information with the previously stored emotional experience. Hence, the impact of early maternal separation and isolation stress (MS) during the stress hyporesponsive period (SHRP) on fear memory retention and sleep in rats were studied. The neonatal rats were subjected to maternal separation and isolation stress during postnatal days 5-7 (6h daily/3d). Polysomnographic recordings and differential fear conditioning was carried out in two different sets of rats aged 2 months. The neuronal replay during REM sleep was analyzed using different parameters. MS rats showed increased time in REM stage and total sleep period also increased. MS rats showed fear generalization with increased fear memory retention than normal control (NC). The detailed analysis of the local field potentials across different time periods of REM sleep showed increased theta oscillations in the hippocampus, amygdala and cortical circuits. Our findings suggest that stress during SHRP has sensitized the hippocampus-amygdala-cortical loops which could be due to increased release of corticosterone that generally occurs during REM sleep. These rats when subjected to fear conditioning exhibit increased fear memory and increased fear generalization. The development of helplessness, anxiety and sleep changes in human patients, thus, could be related to the reduced thermal, tactile and social stimulation during SHRP on brain plasticity and fear memory functions.

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.

Reproductive depression

Reproductive depression is the depression in women that is related to the hormonal changes of the menstrual cycle, pregnancy and the menopause and is manifested clinically as premenstrual depression, postnatal depression and climacteric depression. These three components occur in the same vulnerable women in that a woman with depression in the menopausal transition will usually have a history of premenstrual syndrome (PMS; premenstrual dysphoric disorder [PMDD]), would have been in a good mood during pregnancy and then develop postnatal depression. When the periods return the depression becomes cyclical as PMS. These three conditions are effectively treated with transdermal estrogens which should be the first-choice therapy rather than antidepressants. Estrogens can be used together with antidepressants. The critical time to prevent long-term mood problems is the correct treatment of postnatal depression. In women with low energy and libido, often a side effect of antidepressants, the addition of transdermal testosterone is useful. These women with reproductive depression are often progesterone/progestogen intolerant and a smaller dose or duration of progestogen is a necessary compromise. Alternatively a Mirena IUS or rarely a hysterectomy is required.

Noradrenergic modulation of wakefulness/arousal

The locus coeruleus-noradrenergic system supplies norepinephrine throughout the central nervous system. State-dependent neuronal discharge activity of locus coeruleus noradrenergic neurons has long-suggested a role of this system in the induction of an alert waking state. Work over the past two decades provides unambiguous evidence that the locus coeruleus, and likely other noradrenergic nuclei, exert potent wake-promoting actions via an activation of noradrenergic β- and α₁-receptors located within multiple subcortical structures, including the general regions of the medial septal area, the medial preoptic area and, most recently, the lateral hypothalamus. Conversely, global blockade of β- and α₁-receptors or suppression of norepinephrine release results in profound sedation. The wake-promoting action of central noradrenergic neurotransmission has clinical implications for treatment of sleep/arousal disorders, such as insomnia and narcolepsy, and clinical conditions associated with excessive arousal, such as post-traumatic stress disorder.

Tailoring treatment of depression for women across the reproductive lifecycle: the importance of pregnancy, vasomotor symptoms, and other estrogen-related events in psychopharmacology

Compared with men, women are at increased risk of depression, especially at several reproductive-related lifecycle points. This may be partially due to changing levels of estrogen, a hormone that can affect levels of neurotransmitters and neural proteins. As estrogen levels vary throughout the lifespan, risk of depression in women also varies, and not all treatments are appropriate or effective at all times. In adolescence, onset of depression may be associated with onset of puberty, but treating underage girls with antidepressants can risk suicidality. In females of childbearing age, mood disturbances associated with menstrual cycles signal a risk for later full-blown major depressive disorder. In depressed pregnant and postpartum women, risks of treatment versus risks of nontreatment are intricate and require case-by-case evaluation. In perimenopause, vasomotor symptoms may be harbingers of oncoming depression and also may signal the presence of dysregulated hormones and neurotransmitters. Relieving vasomotor symptoms may be a necessary dimension of treating depression. In postmenopause, response to selected antidepressants may depend on whether the patient is also taking hormone-replacement therapy. To attain optimal outcomes, modern psychopharmacologists must tailor treatment of depression to a woman's reproductive stage of life.

Noradrenergic modulation of arousal

Through a highly divergent efferent projection system, the locus coeruleus-noradrenergic system supplies norepinephrine throughout the central nervous system. State-dependent neuronal discharge activity of locus coeruleus neurons has long-suggested a role of this system in the induction of an alert waking state. More recent work supports this hypothesis, demonstrating robust wake-promoting actions of the locus coeruleus-noradrenergic system. Norepinephrine enhances arousal, in part, via actions of beta- and alpha1-receptors located within multiple subcortical structures, including the general regions of the medial septal area and the medial preoptic areas. Recent anatomical studies suggest that arousal-enhancing actions of norepinephrine are not limited to the locus coeruleus system and likely include the A1 and A2 noradrenergic cell groups. Thus, noradrenergic modulation of arousal state involves multiple noradrenergic systems acting within multiple subcortical regions. Pharmacological studies indicate that the combined actions of these systems are necessary for the sustained maintenance of arousal levels associated with spontaneous waking. Enhanced arousal state is a prominent aspect of both stress and psychostimulant drug action and evidence indicates that noradrenergic systems likely play an important role in both stress-related and psychostimulant-induced arousal. These and other observations suggest that the dysregulation of noradrenergic neurotransmission could well contribute to the dysregulation of arousal associated with a variety of behavioral disorders including insomnia and stress-related disorders.

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.