Marco Luppi

The Inhibition of Neurons in the Central Nervous Pathways for Thermoregulatory Cold Defense Induces a Suspended Animation State in the Rat

The possibility of inducing a suspended animation state similar to natural torpor would be greatly beneficial in medical science, since it would avoid the adverse consequence of the powerful autonomic activation evoked by external cooling. Previous attempts to systemically inhibit metabolism were successful in mice, but practically ineffective in nonhibernators. Here we show that the selective pharmacological inhibition of key neurons in the central pathways for thermoregulatory cold defense is sufficient to induce a suspended animation state, resembling natural torpor, in a nonhibernator. In rats kept at an ambient temperature of 15°C and under continuous darkness, the prolonged inhibition (6 h) of the rostral ventromedial medulla, a key area of the central nervous pathways for thermoregulatory cold defense, by means of repeated microinjections (100 nl) of the GABAA agonist muscimol (1 mm), induced the following: (1) a massive cutaneous vasodilation; (2) drastic drops in deep brain temperature (reaching a nadir of 22.44 ± 0.74°C), heart rate (from 440 ± 13 to 207 ± 12 bpm), and electroencephalography (EEG) power; (3) a modest decrease in mean arterial pressure; and (4) a progressive shift of the EEG power spectrum toward slow frequencies. After the hypothermic bout, all animals showed a massive increase in NREM sleep Delta power, similarly to that occurring in natural torpor. No behavioral abnormalities were observed in the days following the treatment. Our results strengthen the potential role of the CNS in the induction of hibernation/torpor, since CNS-driven changes in organ physiology have been shown to be sufficient to induce and maintain a suspended animation state.

The direct cooling of the preoptic-hypothalamic area elicits the release of thyroid stimulating hormone during wakefulness but not during REM sleep.

Thermoregulatory responses to temperature changes are not operant during REM sleep (REMS), but fully operant in non-REM sleep and wakefulness. The specificity of the relationship between REMS and the impairment of thermoregulation was tested by eliciting the reflex release of Thyrotropin Releasing Hormone (TRH), which is integrated at hypothalamic level. By inducing the sequential secretion of Thyroid Stimulating Hormone (TSH) and Thyroid Hormone, TRH intervenes in the regulation of obligatory and non-shivering thermogenesis. Experiments were performed on male albino rats implanted with epidural electrodes for EEG recording and 2 silver-copper wire thermodes, bilaterally placed in the preoptic-hypothalamic area (POA) and connected to small thermoelectric heat pumps driven by a low-voltage high current DC power supply. In preliminary experiments, a thermistor was added in order to measure hypothalamic temperature. The activation of TRH hypophysiotropic neurons by the thermode cooling of POA was indirectly assessed, in conditions in which thermoregulation was either fully operant (wakefulness) or not operant (REMS), by a radioimmunoassay determination of plasmatic levels of TSH. Different POA cooling were performed for 120 s or 40 s at current intensities of 80 mA and 125 mA, respectively. At both current intensities, POA cooling elicited, with respect to control values (no cooling current), a significant increase in plasmatic TSH levels in wakefulness, but not during REMS. These results confirm the inactivation of POA thermal sensitivity during REMS and show, for the first time, that this inactivation concerns also the fundamental endocrine control of non-shivering thermogenesis.

Enhanced slow-wave EEG activity and thermoregulatory impairment following the inhibition of the lateral hypothalamus in the rat.

Neurons within the lateral hypothalamus (LH) are thought to be able to evoke behavioural responses that are coordinated with an adequate level of autonomic activity. Recently, the acute pharmacological inhibition of LH has been shown to depress wakefulness and promote NREM sleep, while suppressing REM sleep. These effects have been suggested to be the consequence of the inhibition of specific neuronal populations within the LH, i.e. the orexin and the MCH neurons, respectively. However, the interpretation of these results is limited by the lack of quantitative analysis of the electroencephalographic (EEG) activity that is critical for the assessment of NREM sleep quality and the presence of aborted NREM-to-REM sleep transitions. Furthermore, the lack of evaluation of the autonomic and thermoregulatory effects of the treatment does not exclude the possibility that the wake-sleep changes are merely the consequence of the autonomic, in particular thermoregulatory, changes that may follow the inhibition of LH neurons. In the present study, the EEG and autonomic/thermoregulatory effects of a prolonged LH inhibition provoked by the repeated local delivery of the GABAA agonist muscimol were studied in rats kept at thermoneutral (24°C) and at a low (10°C) ambient temperature (Ta), a condition which is known to depress sleep occurrence. Here we show that: 1) at both Tas, LH inhibition promoted a peculiar and sustained bout of NREM sleep characterized by an enhancement of slow-wave activity with no NREM-to-REM sleep transitions; 2) LH inhibition caused a marked transitory decrease in brain temperature at Ta 10°C, but not at Ta 24°C, suggesting that sleep changes induced by LH inhibition at thermoneutrality are not caused by a thermoregulatory impairment. These changes are far different from those observed after the short-term selective inhibition of either orexin or MCH neurons, suggesting that other LH neurons are involved in sleep-wake modulation.

Changes in EEG activity and hypothalamic temperature as indices for non-REM sleep to REM sleep transitions

A shift of physiological regulations from a homeostatic to a non-homeostatic modality characterizes the passage from non-NREM sleep (NREMS) to REM sleep (REMS). In the rat, an EEG index which allows the automatic scoring of transitions from NREMS to REMS has been proposed: the NREMS to REMS transition indicator value, NIV [J.H. Benington et al., Sleep 17 (1994) 28-36]. However, such transitions are not always followed by a REMS episode, but are often followed by an awakening. In the present study, the relationship between changes in EEG activity and hypothalamic temperature (Thy), taken as an index of autonomic activity, was studied within a window consisting of the 60s which precedes a state change from a consolidated NREMS episode. Furthermore, the probability that a transition would lead to REMS or wake was analysed. The results showed that, within this time window, both a modified NIV (NIV(60)) and the difference between Thy at the limits of the window (Thy(D)) were related to the probability of REMS onset. Both the relationship between the indices and the probability of REMS onset was sigmoid, the latter of which saturated at a probability level around 50-60%. The efficacy for the prediction of successful transitions from NREMS to REMS found using Thy(D) as an index supports the view that such a transition is a dynamic process where the physiological risk to enter REMS is weighted at a central level.

Waking and Sleeping following Water Deprivation in the Rat

Wake-sleep (W-S) states are affected by thermoregulation. In particular, REM sleep (REMS) is reduced in homeotherms under a thermal load, due to an impairment of hypothalamic regulation of body temperature. The aim of this work was to assess whether osmoregulation, which is regulated at a hypothalamic level, but, unlike thermoregulation, is maintained across the different W-S states, could influence W-S occurrence. Sprague-Dawley rats, kept at an ambient temperature of 24°C and under a 12 h∶12 h light-dark cycle, were exposed to a prolonged osmotic challenge of three days of water deprivation (WD) and two days of recovery in which free access to water was restored. Two sets of parameters were determined in order to assess: i) the maintenance of osmotic homeostasis (water and food consumption; changes in body weight and fluid composition); ii) the effects of the osmotic challenge on behavioral states (hypothalamic temperature (Thy), motor activity, and W-S states). The first set of parameters changed in WD as expected and control levels were restored on the second day of recovery, with the exception of urinary Ca++ that almost disappeared in WD, and increased to a high level in recovery. As far as the second set is concerned, WD was characterized by the maintenance of the daily oscillation of Thy and by a decrease in activity during the dark periods. Changes in W-S states were small and mainly confined to the dark period: i) REMS slightly decreased at the end of WD and increased in recovery; ii) non-REM sleep (NREMS) increased in both WD and recovery, but EEG delta power, a sign of NREMS intensity, decreased in WD and increased in recovery. Our data suggest that osmoregulation interferes with the regulation of W-S states to a much lesser extent than thermoregulation.

REM Sleep and Endothermy: Potential Sites and Mechanism of a Reciprocal Interference

Numerous data show a reciprocal interaction between REM sleep and thermoregulation. During REM sleep, the function of thermoregulation appears to be impaired; from the other hand, the tonic activation of thermogenesis, such as during cold exposure, suppresses REM sleep occurrence. Recently, both the central neural network controlling REM sleep and the central neural network controlling thermoregulation have been progressively unraveled. Thermoregulation was shown to be controlled by a central “core” circuit, responsible for the maintenance of body temperature, modulated by a set of accessory areas. REM sleep was suggested to be controlled by a group of hypothalamic neurons overlooking at the REM sleep generating circuits within the brainstem. The two networks overlap in a few areas, and in this review, we will suggest that in such overlap may reside the explanation of the reciprocal interaction between REM sleep and thermoregulation. Considering the peculiar modulation of thermoregulation by REM sleep the result of their coincidental evolution, REM sleep may therefore be seen as a period of transient heterothermy.

A Randomized Controlled Trial of Listening to Recorded Music for Heart Failure Patients: Study Protocol.

AIMS To describe a conceptual framework and to test the effectiveness of a recorded music-listening protocol on symptom burden and quality of life in heart failure (HF) patients. BACKGROUND Heart failure is an important public health problem. Many HF patients experience symptoms burden and poor quality of life, even with current improvements in pharmacological treatments. Recorded music listening has been shown to improve outcomes in cardiovascular patients, but it has never been tested on HF patients and with a specific music protocol and a randomized controlled trial methodology. METHODS This study is a multicenter blinded randomized controlled trial that will involve 150 patients. Eligible patients will have a diagnosis of HF, in New York Heart Association functional classification of I to III, and will be recruited from 3 large hospitals in Northern Italy. Patients will be randomly allocated in a 1:1 ratio to receive recorded music-listening intervention with or without standard care for 3 months. Data will be collected at baseline and at the end of the first, second, and third month during the intervention, and at 6 months for follow-up. The following variables will be collected from HF patients with validated protocols: quality of life (primary endpoint), use of emergency services, rehospitalization rates, all cause mortality, self-care, somatic symptoms, quality of sleep, anxiety and depression symptoms, and cognitive function. DISCUSSION This study will examine the effect of recorded music listening on HF patients and will inform clinical practice. If the findings are found to be positive, the protocol could be used as a tool for evidence-based applications of recorded music in HF patients. The framework developed in this study may be helpful for future research focused on the effects of music in HF patients.

MCH and Thermoregulation

Homeothermy represents a remarkable step in animal evolution, albeit at a very high cost in terms of metabolic demand. The maintenance of core body temperature in mammals represents one of the prominent physiological components contributing to the basal metabolic rate. Homeostatic thermoregulation is coordinated by the central nervous system by means of different strategies, spanning from behavioral modifications, aimed at finding a better environment, to the activation or inhibition of key regulatory mechanisms, which are mainly driven by the autonomic nervous system. The hypothalamic neuropeptide MCH plays a pivotal role in regulating basal metabolism, and the activation of this system results in a slowing down of the metabolic rate and also stimulates food intake. On the contrary, blocking the MCH system, in animal models, promotes a lean phenotype with higher body temperature. Even though MCH is not involved in thermoregulatory processes, modifying MCH activity induces metabolic rate modifications, and thermoregulation is modified accordingly. The activation of the MCH system also leads to the dampening of the normal daily oscillation of body temperature. The well-known involvement of MCH in wake-sleep cycle regulation, by stabilizing sleep, and in particular REM sleep, reinforces the hypothesis that the functions of metabolism, thermoregulation, and sleep regulation are closely linked.

Effects of Listening to Live Singing in Patients Undergoing Hemodialysis: A Randomized Controlled Crossover Study

Background: Participation in music therapy is associated with improved psychological and physical indices among chronically ill patients. Listening to music during hemodialysis treatments positively affects patients’ hemodynamics, laboratory values, quality of life, and physical symptoms. The effect of live singing during hemodialysis treatments, however, has not previously been studied. Methods: A total of 24 participants with a diagnosis of end-stage kidney disease participated in the study. The vocalist was a musically trained dialysis nurse. Twelve of the patients listened to 15 min of live singing during 6 consecutive hemodialysis sessions, while the other 12 underwent standard hemodialysis. After a washout period of 2 days, the two groups were reversed. Results: Listening to live music was associated with improvements in systolic and diastolic blood pressure, better quality of sleep, fewer cramps, and reduced anxiety/depression, pain, and itching (p < .05, all values). Conclusions: Listening to live music during hemodialysis is an effective and potentially low-cost therapy for the dialysis care team to employ during hemodialysis treatments.

Wake-sleep and cardiovascular regulatory changes in rats made obese by a high-fat diet

HighlightsDiet‐induced obesity rats sleep more than lean controls during the daily activity period.Diet‐induced obesity rats produces more sequential REM sleep than lean controls.Sleep homeostasis is maintained in diet‐induced obesity rats.Arterial pressure is increased in diet‐induced obesity rats throughout the different wake‐sleep states. ABSTRACT Obesity is known to be associated with alterations in wake‐sleep (WS) architecture and cardiovascular parameters. This study was aimed at assessing the possible influence of diet‐induced obesity (DIO) on sleep homeostasis and on the WS state‐dependent levels of arterial pressure (AP) and heart rate in the rat. Two groups of age‐matched Sprague‐Dawley rats were fed either a high‐fat hypercaloric diet, leading to DIO, or a normocaloric standard diet (lean controls) for 8 weeks. While under general anesthesia, animals were implanted with instrumentation for the recording of electroencephalogram, electromyogram, arterial pressure, and deep brain temperature. The experimental protocol consisted of 48 h of baseline, 12 h of gentle handling, enhancing wake and depressing sleep, and 36‐h post‐handling recovery. Compared to lean controls, DIO rats showed: i) the same amount of rapid‐eye movement (REM) and non‐REM (NREM) sleep in the rest period, although the latter was characterized by more fragmented episodes; ii) an increase in both REM sleep and NREM sleep in the activity period; iii) a comparable post‐handling sleep homeostatic response, in terms of either the degree of Delta power increase during NREM sleep or the quantitative compensation of the REM sleep loss at the end of the 36‐h recovery period; iv) significantly higher levels of AP, irrespectively of the different WS states and of the changes in their intensity throughout the experimental protocol. Overall, these changes may be the reflection of a modification in the activity of the hypothalamic areas where WS, autonomic, and metabolic regulations are known to interact.