Fos-immunoreactivity in the hypothalamus: dependency on the diurnal rhythm, sleep, gender, and estrogen

Péterfi, Zoltán; Churchill, Lynn; Hajdu, I.; Obál, F.; Krueger, James M.; Párducz, Á.

doi:10.1016/j.neuroscience.2003.10.047

Cited by 68 publications

(37 citation statements)

References 64 publications

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“…The dSCN has been clearly shown to send afferents to other hypothalamic areas, including a main thermoregulatory area, the POA [30]. According to Fos expression studies in rats [31,32], the number of Fos-IR cells in the dSCN decreases in the light phase when the T cor of animals is maintained at low levels. The food deprivation-induced fall in T cor has been shown to be associated with reduced Fos expression in the dSCN [14].…”

Section: Discussionmentioning

confidence: 99%

Contribution of the Suprachiasmatic Nucleus to the Formation of a Time Memory for Heat Exposure in Rats

et al. 2007

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Abstract:We have reported that after rats were acclimated to heat for about 5 h daily at a fixed time, the pattern of day-night variations of core temperature (T cor ) altered, i.e., their T cor fell, especially during the period when they had previously been exposed to heat. The suprachiasmatic nucleus (SCN) of the hypothalamus is known to be indispensable for the genesis of circadian rhythms of T cor . We therefore investigated the involvement of the SCN in the characteristic fall in T cor in heat-acclimated rats. The rats were exposed to an ambient temperature of 33°C only in the last half of the dark phase for 10 consecutive days. After the heat exposure schedule, the nocturnal pattern of T cor variations and Fos expression in the dorsomedial SCN altered so that the T cor and the number of Fos immunoreactive cells decreased in the last half of the dark phase. The bilateral lesions of the SCN of rats were made electrically, and the electrical lesions of the SCNs abolished the daily cycle of T cor . In the SCN-lesioned rats, theT cor levels were significantly lowered after the 10-day heat exposure schedule. However, their T cor did not specifically drop during the period when they had previously been exposed to heat. These findings suggest that the SCN is crucial for establishing a time memory for heat stress, and it plays a minimal role in heat acclimation-induced changes in T cor in rats.Key words: heat acclimation, circadian rhythm, core temperature, suprachiasmatic nucleus Acclimation to heat has been repeatedly shown to alter core temperature (T cor ) levels and to modify autonomic thermoregulatory functions in various species of animals. When rats are subjected to daily heat exposure limited to about 5 h at a fixed time and then transferred to a constant thermoneutral ambient temperature (T a ), the pattern of day-night variations in their T cor alters so that T cor falls for 3 to 4 h around the period when they were previously exposed to heat [1][2][3]. The newly established pattern of the T cor cycle has been shown to persist for 1, 3, and 6 days after the repetition of timed daily heat exposure for 5, 14, and 28 consecutive days, respectively, with no actual temperature stimuli or time cues [2]. Furthermore, heat acclimation-induced changes in thermoregulatory functions, such as downward shifts of thermoeffector thresholds [4], the enhancement of thermoregulatory responses to acute heat load, and reduced resting metabolic rate [5], were clearly seen during the period of the previous heat exposure time. From these observations, we have proposed that a time memory for heat exposure can be formed in rats as a result of repeated heat exposure limited to a fixed time once a day, and according to this memory, thermoregulatory systems may be activated during the specific period so that their heat tolerance improves [6]; however, the central mechanism for the formation and retention of such a time memory is totally unknown.It is well known that the suprachiasmatic nucleus (SCN) of the hypothalamus acts as an ...

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Section: Discussionmentioning

confidence: 99%

Contribution of the Suprachiasmatic Nucleus to the Formation of a Time Memory for Heat Exposure in Rats

et al. 2007

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“…Sham operation was performed with a knife blade in the front, lowered at Ϫ1.8 mm posterior to bregma until it reached the skull bone at the bottom; no rotation of the knife was performed. The rats were provided with cortical stainless-steel screw electroencephalogram (EEG) electrodes, and a thermistor to record brain temperature (Tbr) (60). Motor activity was determined from signals generated in electromagnetic transducers activated by the movements of the recording cable (60).…”

Section: Surgerymentioning

confidence: 99%

The anterolateral projections of the medial basal hypothalamus affect sleep

Péterfi¹,

Makara²,

Obál³

et al. 2009

American Journal of Physiology-Regulatory, Integrative and Comp

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Peterfi Z, Makara GB, Obál F Jr, Krueger JM. The anterolateral projections of the medial basal hypothalamus affect sleep. Am J Physiol Regul Integr Comp Physiol 296: R1228 -R1238, 2009. First published February 4, 2009 doi:10.1152/ajpregu.90958.2008-The role of the medial basal hypothalamus (MBH) and the anterior hypothalamus/preoptic area (AH/POA) in sleep regulation was investigated using the Halász knife technique to sever MBH anterior and lateral projections in rats. If both lateral and anterior connections of the MBH were cut, rats spent less time in non-rapid eye movement sleep (NREMS) and rapid eye movement sleep (REMS). In contrast, if the lateral connections remained intact, the duration of NREMS and REMS was normal. The diurnal rhythm of NREMS and REMS was altered in all groups except the sham control group. Changes in NREMS or REMS duration were not detected in a group with pituitary stalk lesions. Water consumption was enhanced in three groups of rats, possibly due to the lesion of vasopressin fibers entering the pituitary. EEG delta power during NREMS and brain temperatures (Tbr) were not affected by the cuts during baseline or after sleep deprivation. In response to 4 h of sleep deprivation, only one group, that with the most anterior-to-posterior cuts, failed to increase its NREMS or REMS time during the recovery sleep. After deprivation, Tbr returned to baseline in most of the treatment groups. Collectively, results indicate that the lateral projections of the MBH are important determinants of duration of NREMS and REMS, while more anterior projections are concerned with the diurnal distribution of sleep. Further, the MBH projections involved in sleep regulation are distinct from those involved in EEG delta activity, water intake, and brain temperature.anterior hypothalamus/preoptic area; sleep regulation; non-rapid eye movement sleep A RELATIONSHIP BETWEEN THE somatotropic axis and sleep was first recognized 40 years ago when the association between plasma growth hormone (GH) levels and non-rapid eye movement sleep (NREMS) was described by Takahashi et al. (77). Subsequently, much evidence has supported the hypothesis that hypothalamic growth hormone releasing hormone (GHRH) is involved in NREMS sleep regulation and, through its induction of pituitary release of GH, rapid eye movement sleep (REMS) as well (reviewed in Ref. 55). Within the hypothalamus, the majority of the GHRH-containing perikarya resides in the arcuate nucleus (ARC) (50,51,66). A smaller number of GHRH-containing neurons are found around the ventral border of the ventromedial nucleus, the dorsomedial nucleus, and in the parvocellular portion of the paraventricular nucleus (PVN), and the posterior hypothalamus. Previously, we showed that microinjection of GHRH into the medial preoptic region/anterior hypothalamus promotes NREMS, while injection of a GHRH antagonist peptide inhibited NREMS (80). The stimulated areas likely included the rostral portion of the periventricular (PeV) nucleus due to diffusion. Sites in the posterior...

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“…Original studies on functional mapping of Fos-IR reported low levels of Fos-positive neurons in the MnPN of rats that were sleep deprived compared with spontaneously sleeping rats (Gong et al, 2000), whereas recent studies have reported higher numbers of Fos-immunoreactive neurons (IRNs) in the MnPN of sleep-deprived rats (Modirrousta et al, 2004;Peterfi et al, 2004;Gvilia et al, 2005) and of rapid eye movement (REM) sleepdeprived rats (Gvilia et al, 2006). The number of MnPN and vlPOA GABAergic neurons manifesting Fos-IR is elevated during recovery sleep after total sleep deprivation (Gong et al, 2004) and during recovery sleep after REM-sleep restriction (Gvilia et al, 2006).…”

Section: Introductionmentioning

confidence: 99%