Circadian and estrous cycle-dependent variations in blood pressure and heart rate in female rats

1994 ◽  
Vol 267 (5) ◽  
pp. R1250-R1256 ◽  
Author(s):  
H. Takezawa ◽  
H. Hayashi ◽  
H. Sano ◽  
H. Saito ◽  
S. Ebihara
Keyword(s):  
Heart Rate ◽  
Estrous Cycle ◽  
Female Rats ◽  
Constant Darkness ◽  
Dark Phase ◽  
Daily Rhythms ◽  
Abrupt Decrease ◽  
Internal Phase ◽  
Free Running ◽  
Cycle Dependent

To determine whether cardiovascular functions are controlled by the endogenous circadian system and whether they change with the estrous cycle in female rats, we measured mean arterial pressure (MAP), heart rate (HR), and spontaneous activity (ACT) of female rats using an implantable radiotelemetry device and a computerized data-collecting system. Under a 12:12-h light-dark (LD) cycle, these parameters exhibited daily rhythms that were entrained to the photic cycle. The patterns of the daily rhythms varied with estrous cycles, and variations were particularly marked in the proestrous stage. During the dark period of this stage, ACT levels were significantly higher, but HR was significantly lower than in other stages. Although the peak MAP occurred within 2 h after the onset of the dark phase in three of the estrous stages, it occurred around midnight in the proestrous stage. Such estrous cycle-dependent variations were eliminated by ovariectomy. The implantation of 17 beta-estradiol produced a gradual increase in MAP and an abrupt decrease in HR. During constant darkness, all three parameters were free running, maintaining the same internal phase relationships with each other as during LD cycles. These results indicate that daily variations in these parameters were controlled by the endogenous circadian oscillating system, that they vary with the estrous cycle in female rats, and that estrogen may be responsible for these estrous cycle-dependent variations.

Gonadal hormones organize and modulate the circadian system of the rat

1981 ◽  
Vol 241 (1) ◽  
pp. R62-R66 ◽  
Author(s):  
H. E. Albers
Keyword(s):  
Testosterone Propionate ◽  
Wheel Running ◽  
Activity Rhythm ◽  
Gonadal Hormones ◽  
Circadian System ◽  
Female Rats ◽  
Constant Darkness ◽  
Before And After ◽  
Free Running ◽  
Free Running Period

The circadian wheel-running rhythms of gonadectomized adult male, female, and perinatally androgenized female rats, maintained in constant darkness, were examined before and after implantation of Silastic capsules containing cholesterol (C) or estradiol-17 beta (E). The free-running period of the activity rhythm (tau) before capsule implantation tended to be shorter in animals exposed to perinatal androgen. Administration of C did not reliably alter tau in any group. E significantly shortened tau in 100% of females injected with oil on day 3 of life. In females, injected with 3.5 micrograms testosterone propionate on day 3, and males, E shortened or lengthened tau, with the direction and magnitude of this change in tau inversely related to the length of the individual's pretreatment tau. These data indicate that the presence of perinatal androgen does not eliminate the sensitivity of the circadian system of the rat to estrogen, since estrogen alters tau in a manner that depends on its pretreatment length.

Splitting of the locomotor activity rhythm in rats by exposure to continuous light

1983 ◽  
Vol 244 (4) ◽  
pp. R573-R576 ◽  
Author(s):  
Phyllis W. Cheung ◽  
Charles E. McCormack
Keyword(s):  
Locomotor Activity ◽  
Estrous Cycle ◽  
Activity Rhythm ◽  
Continuous Light ◽  
Female Rats ◽  
Locomotor Rhythm ◽  
Estrous Cycles ◽  
Locomotor Activity Rhythm ◽  
Active Portion ◽  
Free Running

Female rats exposed to low intensities (0.1–1.5 lx) of continuous light (LL), displayed regular estrous cycles and free-running circadian rhythms of locomotor activity. In most rats, as the intensity of LL was increased to >2.0 lx, components within the active portion (α) of the locomotor rhythm remained synchronized as the periodicity of the rhythm lengthened. However, in a few rats agr split into two components; one of which free-ran with a period shorter than 24 h, while the other free-ran with a period longer than 24 h. As soon as the two components became maximally separated they spontaneously rejoined. In most rats, estrous cycles ceased shortly after the intensity of LL was increased to >2.0 lx even though the locomotor activity rhythm retained its unsplit free-running nature. These observations suggest that the multiple oscillators that control the rhythms of locomotor activity and the estrous cycle are normally coupled to one another. In certain intensities of LL, these oscillators uncouple and free-run with different periodicities, a condition which causes estrous cycles to cease and sometimes produces a split locomotor activity rhythm. circadian rhythm; oscillators; estrous cycle Submitted on November 9, 1981 Accepted on October 11, 1982

A circadian rhythm of behavioural thermoregulation in a freshwater gastropod, Helisoma trivolis

1980 ◽  
Vol 58 (11) ◽  
pp. 2152-2155 ◽  
Author(s):  
Martin Kavaliers
Keyword(s):  
Circadian Rhythm ◽  
Constant Darkness ◽  
Dark Phase ◽  
Behavioural Thermoregulation ◽  
Dark Cycle ◽  
Preferred Temperature ◽  
Temperature Selection ◽  
Freshwater Gastropod ◽  
Free Running ◽  
Maximum Temperatures

The behaviour of the aquatic gastropod Helisoma trivolis was examined in a thermal gradient. Under a 12 h light: 12 h dark cycle gastropods displayed a diel rhythm of preferred temperature selection. Maximum temperatures (21–22 °C) were selected during the dark phase and minimum temperatures (17–18 °C) were selected during the light phase of the light–dark cycle. Under constant darkness temperature selection continued as an endogenous free-running circadian rhythm of behavioural thermoregulation.

scholarly journals Chronic stress influences nociceptive sensitivity of female rats in an estrous cycle-dependent manner

Stress ◽  
2019 ◽  
Vol 23 (4) ◽  
pp. 386-392
Author(s):  
Chun-Xiao Yang ◽  
Yi Wang ◽  
Qi Lu ◽  
Yan-Na Lian ◽  
Enoch Odame Anto ◽  
...  
Keyword(s):  
Estrous Cycle ◽  
Chronic Stress ◽  
Female Rats ◽  
Dependent Manner ◽  
Nociceptive Sensitivity ◽  
Cycle Dependent ◽  
Stress Influences

Melatonin administration entrains female rat activity rhythms in constant darkness but not in constant light

1988 ◽  
Vol 255 (2) ◽  
pp. R237-R242
Author(s):  
E. M. Thomas ◽  
S. M. Armstrong
Keyword(s):  
Estrous Cycle ◽  
Activity Rhythm ◽  
Onset Time ◽  
Circadian System ◽  
Female Rats ◽  
Male Rats ◽  
Constant Darkness ◽  
Female Rat ◽  
Continuous Darkness ◽  
Activity Rhythms

In female rats the luteinizing hormone (LH) is timed by the circadian system and is followed by a display of intense, estrogen-induced running behavior. This proestrous running on the night of ovulation can be used as a marker of the estrous cycle. Entrainment of the mammalian circadian system by exogenous melatonin (MT) has been demonstrated only in the activity rhythms of male rats. The present experiments were designed to study the effect of daily MT injections on activity rhythms and proestrous running of female rats in 1) continuous dim white light (LL) and 2) continuous darkness (DD). In LL, MT injections (50 micrograms/kg or 1 mg/kg) had no discernible effect on activity rhythms. In DD, four of the six MT-treated rats (100 micrograms/kg) entrained to the injection, and a fifth animal showed phase advances in its activity rhythm when onset of activity passed through injection time. The sixth animal was not injected with MT at activity onset time. None of the six control animals showed either effect. MT had no effect on the length of the estrous cycle. Thus MT injections can entrain circadian rhythms of activity and proestrous running in female rats in DD but not in LL.

scholarly journals Cardiac Neural Regulation Oscillates with the Estrous Cycle in Freely Moving Female Rats: The Role of Endogenous Estrogens

Endocrinology ◽  
2010 ◽  
Vol 151 (6) ◽  
pp. 2613-2621 ◽  
Author(s):  
Terry B. J. Kuo ◽  
C. T. Lai ◽  
Fu-Chun Hsu ◽  
Yi-Jhan Tseng ◽  
Jia-Yi Li ◽  
...  
Keyword(s):  
Heart Rate ◽  
Heart Rate Variability ◽  
Estrous Cycle ◽  
Sympathetic Activity ◽  
Low Frequency ◽  
Female Rats ◽  
Tamoxifen Treatment ◽  
Freely Moving ◽  
Low Frequency Power ◽  
Frequency Power

Both estrogens levels and sleep/wakefulness states have been separately reported to affect cardiac autonomic regulation. In this study, we examined the integrated effects of the estrous and sleep cycles on cardiac autonomic activity in freely moving adult female rats. Cardiac autonomic activities were measured by analyzing the power spectrum of heart rate variability. High-frequency power (HF) and low-frequency power to HF ratio are closely correlated with cardiac parasympathetic and sympathetic activity, respectively. Ten days after electrodes were implanted, electroencephalogram, electromyogram, and electrocardiogram were recorded 6 h daily for 12 consecutive days to cover at least two estrous cycles. Estrous-cycle stages were determined using vaginal smears. Sleep cycle-related heart rate variability parameter oscillations were seen in all rats. However, the estrous cyclicity and estrous-cycle-related changes were only observed in the control rats and not in ovariectomized or the estrogen receptor antagonist, tamoxifen, treatment rats. A significantly higher HF was observed in estrous rats compared with diestrous rats or ovariectomized rats no matter whether the rats were asleep or awake. However, a significantly low-frequency power to HF ratio was only observed in quiet sleep (QS) during estrus. All these differences disappeared after treatment with tamoxifen. Our results suggest that estrous-cycle-related changes in cardiac neural regulations can be mainly attributed to endogenous estrogens, and these effects are most obviously manifest during QS. Estrous rats during QS would be equivalent to the late follicular phase of the women menstrual cycle and involve strong vagal tone but weak sympathetic activity.

Sex and hormonal cycle differences in rat brain levels of pain-related cannabimimetic lipid mediators

2006 ◽  
Vol 291 (2) ◽  
pp. R349-R358 ◽  
Author(s):  
Heather B. Bradshaw ◽  
Neta Rimmerman ◽  
Jocelyn F. Krey ◽  
J. Michael Walker
Keyword(s):  
Sex Differences ◽  
Estrous Cycle ◽  
Lipid Mediators ◽  
Female Rats ◽  
Male Rats ◽  
Sexually Dimorphic ◽  
Hormonal Cycle ◽  
Time Period ◽  
Cycle Dependent ◽  
Arachidonoyl Glycerol

One important function of endocannabinoids and related lipid mediators in mammalian central nervous system is modulation of pain. Evidence obtained during the last decade shows that altered levels of these compounds in the brain accompany decreases in pain sensitivity. Such changes, if sexually dimorphic, could account for sex differences in pain and differences that occur during different phases of the hormonal cycle in females. To examine this possibility, we measured the levels of the pain-modulatory lipids anandamide, 2-arachidonoyl glycerol, N-arachidonoyl glycine, N-arachidonoyl gamma amino butyric acid, and N-arachidonoyl dopamine in seven different brain areas (pituitary, hypothalamus, thalamus, striatum, midbrain, hippocampus, and cerebellum) in male rats, and in female rats at five different points in the estrous cycle. The cerebellum did not demonstrate a change in endocannabinoid production across the estrous cycle, whereas all other areas tested showed significant differences in at least one of the compounds measured. These changes in levels occurred predominantly within the 36-h time period surrounding ovulation and behavioral estrus. Differences between males and females were measured as either estrous cycle-independent (all estrous cycles combined) or cycle-dependent (comparisons of males to each estrous cycle). In cycle-independent analyses, small sex differences were observed in the pituitary, hypothalamus, cerebellum, and striatum, whereas no differences were observed in the thalamus, midbrain, and hippocampus. In cycle-dependent analyses, the hypothalamus and pituitary showed largest sex differences followed by the striatum, midbrain, and hippocampus, whereas no sex differences were measured in thalamus and cerebellum. These data provide a basis for investigations into how differences in sex and hormonal status play a role in mechanisms regulating endocannabinoid production and pain.

Palatable high-fat diet intake influences mnemonic and emotional aspects in female rats in an estrous cycle-dependent manner

2021 ◽  
Author(s):  
Sara Pereira Silva ◽  
José Ivo Araújo Beserra-Filho ◽  
Melina Chiemi Kubota ◽  
Gabriela Nascimento Cardoso ◽  
Francisca Rayanne Silva Freitas ◽  
...  
Keyword(s):  
Estrous Cycle ◽  
High Fat Diet ◽  
Female Rats ◽  
Dependent Manner ◽  
High Fat ◽  
Emotional Aspects ◽  
Diet Intake ◽  
Cycle Dependent

The chronobiology of the brushtail possum, Trichosurus vulpecula (Marsupialia:Phalangeridae): tests of internal and external control of timing

1999 ◽  
Vol 47 (6) ◽  
pp. 579 ◽  
Author(s):  
P. A. Herbert ◽  
R. D. Lewis
Keyword(s):  
Internal Control ◽  
Internal Clock ◽  
External Control ◽  
Constant Darkness ◽  
Brushtail Possum ◽  
Dark Phase ◽  
Trichosurus Vulpecula ◽  
Direct Response ◽  
Natural Behaviour ◽  
Free Running

The chronobiology of the brushtail possum (Trichosurus vulpecula) was investigated in a vivarium and in light-controlled cabinets to determine what controls the timing of natural patterns of activity and rest. It is proposed that the timing of natural behaviour of the possum is not regulated entirely by direct response to environmental factors, but that it may have an element of internal control. Unless perturbed by wind and/or rain, the onset of activity is precisely timed each day, beginning as light intensity declines following sunset. In tests of an internal clock hypothesis, possums in constant darkness exhibited free-running circadian rhythms of activity with periods initially slightly shorter than 24 h, spontaneously reducing to c.22 h 40 min after c. 40 days. The internal rhythm of the possum could be entrained by 24-h light/dark cycles with activity initiated at the onset of the dark phase. We propose that the timing of the onset of natural behaviour of the possum is controlled through the output of a circadian clock that may be modulated by direct responses to wind and rain.

CIRCADIAN RHYTHM OF PLASMA CORTICOSTEROID IN ADULT FEMALE RATS: CHRONOLOGICAL SHIFTS IN ABNORMAL LIGHTING REGIMENS AND CONNECTION WITH OESTROUS CYCLE

1975 ◽  
Vol 80 (3) ◽  
pp. 527-541 ◽  
Author(s):  
Yasuhiko Morimoto ◽  
Tatsuo Oishi ◽  
Kazutaka Arisue ◽  
Zensuke Ogawa ◽  
Fumiko Tanaka ◽  
...  
Keyword(s):  
Circadian Rhythm ◽  
Adult Female ◽  
Female Rats ◽  
Constant Light ◽  
Constant Darkness ◽  
Vaginal Smear ◽  
Free Running ◽  
Normal Light ◽  
Lighting Regimen ◽  
Day By Day

ABSTRACT The circadian rhythm of plasma corticosteroid (CS) levels in adult female rats was studied chronologically under the following conditions: normal light-dark (LD), inverted light-dark (DL), constant dark (DD) and constant light (LL). Animals were accustomed to LD condition for 7 days before exposure to each abnormal lighting regimen. Normal circadian rhythm established under LD condition was clearly inverted on the third day of DL regimen, and the inverted rhythm persisted thereafter under DL condition. The circadian CS rhythm persisted essentially unchanged throughout DD condition, but lost its regular periodicity showing "free running" and changed day by day under LL condition. The average CS levels over a 24 h period were higher under LL than under DD condition. Plasma CS levels in each lighting regimen exhibited diurnal variations regardless of the vaginal smear patterns of autopsied animals. Exposure of rats to LL for 21 days made the circadian CS rhythm flat, but induced persistent oestrus in only a few animals. The data suggest that (1) an unexpectedly rapid inversion of the circadian CS rhythm occurs if animals are exposed to inverted light-dark environment; (2) constant darkness seems to be a near-natural environment for rats, and changes little of the pre-established circadian CS rhythm; (3) constant light, on the contrary, is assumed to be a stress for rats, and disrupts the circadian CS rhythm and elevates CS levels; (4) the change in circadian CS rhythm in adult female rats is not mediated by a change in gonadal function and the two conditions may not be connected directly with each other.

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