Chronic lack of hypocretin signaling may entail consequences on blood pressure that are potentially adverse and that vary widely among wake-sleep states.

Cortelli P. Sleep-dependent changes in the coupling between heart period and blood pressure in human subjects. We investigated whether in human subjects, the pattern of coupling between the spontaneous fluctuations of heart period (HP) and those of systolic blood pressure (SBP) differs among wake-sleep states. Polysomnographic recordings and finger blood pressure measurements were performed for 48 h in 15 nonobese adults without sleep-disordered breathing. The cross-correlation function (CCF) between the fluctuations of HP and SBP at frequencies Ͻ0.15 Hz was computed during quiet wakefulness (QW), light (stages 1 and 2) and deep (stages 3 and 4) nonrapid-eye-movement sleep (NREMS), and rapid-eye-movement sleep (REMS). A positive correlation between HP and the previous SBP values, which is the expected result of baroreflex feedback control, was observed in the sleep states but not in QW. In deep NREMS, the maximum CCF value was significantly higher than in any other state, suggesting the greatest baroreflex contribution to the coupling between HP and SBP. A negative correlation between HP and the subsequent SBP values was also observed in each state, consistent with the mechanical feed-forward action of HP on SBP and with central autonomic commands. The contribution of these mechanisms to the coupling between HP and SBP, estimated from the minimum CCF value, was significantly lower in deep NREMS than either in light NREMS or QW. These results indicate that the pattern of coupling between HP and SBP at low frequencies differs among wake-sleep states in human subjects, with deep NREMS entailing the highest feedback contribution of the baroreflex and a low effectiveness of feed-forward mechanisms.feedback and feed-forward mechanisms; baroreflex; central autonomic commands; cross-correlation analysis; sequence technique THE PATTERN OF COUPLING BETWEEN the spontaneous fluctuations of heart period (HP) and those of blood pressure indicates the contribution of different mechanisms to cardiovascular control during real-life behavior. In particular, a positive correlation between HP and the previous pressure values is the expected result of the arterial baroreflex, which acts as a delayed negative-feedback control (37). In turn, the fluctuations of HP may alter cardiac output, eliciting pressure fluctuations that are negatively correlated with them. Central autonomic commands (15) cause opposite changes in HP and vascular resistance (13), thereby apparently enhancing this feed-forward interaction.In animal models, the pattern of coupling between HP and blood pressure suggests a variable contribution of central and baroreflex mechanisms to cardiovascular control in different wake-sleep states (33,34,39). The baroreflex contribution appears most prominent during quiet sleep in lambs (33) and during nonrapid-eye-movement sleep (NREMS) in rats (34,39). On the other hand, in rapid-eye-movement sleep (REMS), the contribution of feed-forward mechanisms prevails in rats due to central autonomic commands (6,34,39), which manifest a...

Rolipram, a type IV-specific phosphodiesterase inhibitor, is known to improve memory under various learning tasks. Moreover, Rolipram treatments have been shown to increase expression and phosphorylation of a key factor for hippocampal memory consolidation, the cAMP-dependent response element-binding protein, CREB. However, the exact correlation between hippocampal CREB phosphorylation and memory improvement induced by Rolipram has not yet been determined in a CREB-dependent type of hippocampal-related learning in normogenic, intact rodents. Here, we report that subchronic Rolipram delivery by using osmotic minipumps increased the basal rat hippocampal expression and phosphorylation of CREB, as well as the expression of the cAMPdependent, memory-related protein, Arc. In parallel, the same treatment improved memory consolidation of conditioned fear. Furthermore, the increase of CREB phosphorylation and Arc expression consequent to the learning experience was enhanced in Rolipram-treated rats, compared to controls. By evaluating the time course of memory extinction over 10 days after the initial learning test, we also observed significant slowing down of the memory extinction rate in Rolipram-treated rats. This effect could be attributed to CREB phosphorylation and memory having been initially higher, as osmotic minipumps stopped to release Rolipram the first day after the initial learning test. Our data define the conditions through which the pharmacological manipulation of hippocampal CREB expression and activation result in memory amelioration in normogenic, intact animals. These results are relevant for the study of molecular correlates of memory, and may also be important in view of the efforts to design new pharmacological treatments, targeting the CREB pathway and leading to enhancement of learning and memory, even in the absence of patent neuropathology.

The central neural pathways underlying the physiological coordination between thermoregulation and the controls of the wake-sleep behavior and cardiovascular function remain insufficiently understood. Growing evidence supports the involvement of hypocretin (orexin) peptides in behavioral, cardiovascular, and thermoregulatory functions. We investigated whether the effects of ambient temperature on wake-sleep behavior and cardiovascular control depend on the hypothalamic neurons that release hypocretin peptides. Orexin-ataxin3 transgenic mice with genetic ablation of hypocretin neurons (n = 11) and wild-type controls (n = 12) were instrumented with electrodes for sleep scoring and a telemetric blood pressure transducer. Simultaneous sleep and blood pressure recordings were performed on freely-behaving mice at ambient temperatures ranging between mild cold (20°C) and the thermoneutral zone (30°C). In both mouse groups, the time spent awake and blood pressure were higher at 20°C than at 30°C. The cold-related increase in blood pressure was significantly smaller in rapid-eye-movement sleep (REMS) than either in non-rapid-eye-movement sleep (NREMS) or wakefulness. Blood pressure was higher in wakefulness than either in NREMS or REMS at both ambient temperatures. This effect was significantly blunted in orexin-ataxin3 mice irrespective of ambient temperature and particularly during REMS. These data demonstrate that hypocretin neurons are not a necessary part of the central pathways that coordinate thermoregulation with wake-sleep behavior and cardiovascular control. Data also support the hypothesis that hypocretin neurons modulate changes in blood pressure between wakefulness and the sleep states. These concepts may have clinical implications in patients with narcolepsy with cataplexy, who lack hypocretin neurons.

Abstract-Leptin increases sympathetic activity, possibly contributing to hypertension in obese subjects. Hypertension increases cardiovascular mortality, with nighttime (sleep) blood pressure having a substantial prognostic value. We measured blood pressure in male leptin-deficient obese mice (ob/ob; nϭ7) and their lean wild-type littermates (ϩ/ϩ; nϭ11) during wakefulness, non-rapid-eye-movement sleep, and rapid-eye-movement sleep to investigate whether, in the absence of leptin, derangements of blood pressure are still associated with obesity and depend on the wake-sleep state. Mice were implanted with a telemetric pressure transducer and electrodes for discriminating wake-sleep states. Mean blood pressure was significantly higher in ob/ob than in ϩ/ϩ mice during wakefulness (7.3Ϯ2.6 mm Hg) and non-rapid-eye-movement sleep (6.7Ϯ2.8 mm Hg) but not during rapid-eye-movement sleep (2.6Ϯ2.6 mm Hg). In ob/ob and ϩ/ϩ mice, mean blood pressure was substantially higher during wakefulness than during non-rapid-eye-movement sleep. On passing from non-rapid-eye-movement sleep to rapid-eye-movement sleep, mean blood pressure decreased significantly in ob/ob but not in ϩ/ϩ mice. The time spent during wakefulness was lower in ob/ob than in ϩ/ϩ mice during the dark (active) period, whereas the opposite occurred during the light (rest) period. Consequently, mean blood pressure was significantly higher in ob/ob than in ϩ/ϩ mice during the light (8.2Ϯ2.4 mm Hg) but not during the dark (3.0Ϯ2.9 mm Hg) period. These data suggest that, in the absence of leptin, obesity may entail hypertensive derangements of blood pressure, which are substantially modulated by the cardiovascular effects of the wakesleep states. Key Words: arterial pressure Ⅲ behavior Ⅲ heart rate Ⅲ hypertension Ⅲ obesity Ⅲ investigative techniques Ⅲ mice O besity is a threat to health care because it is rapidly increasing in prevalence 1 and is associated with hypertension and cardiovascular risk. 2 The hormone leptin signals the abundance of fat stores and acts on the hypothalamus to mount adaptive adjustments of energy balance. 3 Leptin also increases sympathetic activity and blood pressure (BP). 4 -6 Diet-induced obesity entails hyperleptinemia and resistance to the anorectic but not to the cardiovascular effects of leptin, 7 which may, thus, contribute to obesityrelated hypertension. 8,9 Mutations that cause a lack of leptin or leptin receptors cause morbid obesity, 3 allowing us to disentangle the cardiovascular correlates of obesity from those of hyperleptinemia. Although values of BP in the hypertensive range have been reported in obese subjects with congenital leptin deficiency, 10 evidence of hypertension is not consistent in this rare form of obesity. 11 Evidence is inconsistent also on obese mice with congenital impairment of leptin signaling, in which either hypotensive 12-14 or hypertensive 15-17 derangements of BP have been reported. In these mice, the occurrence 15 or severity 17 of hypertension vary between the light and dark periods, which entail ...

In the present experiments, we used conditioned fear to study whether changes in expression or functional state of proteins known to be involved in hippocampal learning could suggest correlation with age-related memory deficits. We focused on both alterations constitutively present in the hippocampus of aged rats and alterations related to different learning responses. Our results point at the dysregulation of the phosphorylation state of CREB in the hippocampus of aged rats as a primary biochemical correlate of their impaired memory. Other proteins, known to be important for various steps of memory formation and consolidation and linked to CREB, are to some extent altered in their constitutive expression or in the response to learning in the aged hippocampus. In particular, phosphorylated CREB and Arc, a protein functionally related to CREB in memory consolidation, are both present at constitutively higher levels in the hippocampus of aged rats, but they are not susceptible to the learning-related up-regulation occurring in young adults. Two other CREB-regulated proteins involved in memory consolidation, the neurotrophin BDNF and the transcription factor C/EBPbeta, are expressed at similar levels in the hippocampus of young-adult and aged rats, but their response to conditioned fear learning appears dysregulated by aging. Calcineurin, a protein phosphatase having CREB among its substrates and whose expression negatively correlates with learning, is more expressed in the hippocampus of aged rats. However, while calcineurin expression decreases in the hippocampus of young adults after learning, no changes are observed in the hippocampus of aged, learning-impaired rats.

A major limitation in the study of sleep breathing disorders in mouse models of pathology is the need to combine whole-body plethysmography (WBP) to measure respiration with electroencephalography/electromyography (EEG/EMG) to discriminate wake-sleep states. However, murine wake-sleep states may be discriminated from breathing and body movements registered by the WBP signal alone. Our goal was to compare the EEG/EMG-based and the WBP-based scoring of wake-sleep states of mice, and provide formal guidelines for the latter. EEG, EMG, blood pressure and WBP signals were simultaneously recorded from 20 mice. Wake-sleep states were scored based either on EEG/EMG or on WBP signals and sleep-dependent respiratory and cardiovascular estimates were calculated. We found that the overall agreement between the 2 methods was 90%, with a high Cohen’s Kappa index (0.82). The inter-rater agreement between 2 experts and between 1 expert and 1 naïve sleep investigators gave similar results. Sleep-dependent respiratory and cardiovascular estimates did not depend on the scoring method. We show that non-invasive discrimination of the wake-sleep states of mice based on visual inspection of the WBP signal is accurate, reliable and reproducible. This work may set the stage for non-invasive high-throughput experiments evaluating sleep and breathing patterns on mouse models of pathophysiology.

A recently discovered neurodevelopmental disorder caused by the mutation of the cyclin-dependent kinase-like 5 gene (CDKL5) entails complex autistic-like behaviours similar to Rett syndrome, but its impact upon physiological functions remains largely unexplored. Sleep-disordered breathing is common and potentially life-threatening in patients with Rett syndrome; however, evidence is limited in children with CDKL5 disorder, and is lacking altogether in adults. The aim of this study was to test whether the breathing pattern during sleep differs between adult Cdkl5 knockout (Cdkl5-KO) and wild-type (WT) mice. Using whole-body plethysmography, sleep and breathing were recorded non-invasively for 8 h during the light period. Sleep apneas occurred more frequently in Cdkl5-KO than in WT mice. A receiver operating characteristic (ROC) analysis discriminated Cdkl5-KO significantly from WT mice based on sleep apnea occurrence. These data demonstrate that sleep apneas are a core feature of CDKL5 disorder and a respiratory biomarker of CDKL5 deficiency in mice, and suggest that sleep-disordered breathing should be evaluated routinely in CDKL5 patients.