Sex and estrous cycle differences in the behavioral effects of high-strength static magnetic fields: role of ovarian steroids

2006 ◽  
Vol 290 (3) ◽  
pp. R659-R667 ◽  
Author(s):  
Angie M. Cason ◽  
Megan DenBleyker ◽  
Kimberly Ferrence ◽  
James C. Smith ◽  
Thomas A. Houpt
Keyword(s):  
Magnetic Fields ◽  
Estrous Cycle ◽  
Hormone Replacement ◽  
High Strength ◽  
Behavioral Effects ◽  
Female Rats ◽  
Male Rats ◽  
Static Magnetic Fields ◽  
Ovarian Steroids ◽  
Intact Rats

Advances in magnetic resonance imaging are driving the development of higher-resolution machines equipped with high-strength static magnetic fields (MFs). The behavioral effects of high-strength MFs are largely uncharacterized, although in male rats, exposure to 7 T or above induces locomotor circling and leads to a conditioned taste avoidance (CTA) if paired with a novel taste. Here, the effects of MFs on male and female rats were compared to determine whether there are sex differences in behavioral responses and whether these can be explained by ovarian steroid status. Rats were given 10-min access to a novel saccharin solution and then restrained within a 14-T magnet for 30 min. Locomotor activity after exposure was scored for circling and rearing. CTA extinction was measured with two-bottle preference tests. In experiment 1, males were compared with females across the estrous cycle after a single MF exposure. Females circled more and acquired a more persistent CTA than males; circling was highest on the day of estrus. In experiment 2, the effects of three MF exposures were compared among intact rats, ovariectomized females, and ovariectomized females with steroid replacement. Compared with intact rats, ovariectomy increased circling; estrogen replacement blocked the increase. Males acquired a stronger initial CTA but extinguished faster than intact or ovariectomized females. Thus the locomotor circling induced by MF exposure was increased in females and modulated by ovarian steroids across the estrous cycle and by hormone replacement. Furthermore, female rats acquired a more persistent CTA than male rats, which was not dependent on estrous phase or endogenous ovarian steroids.

scholarly journals Behavioral Effects of High-Strength Static Magnetic Fields on Rats

2003 ◽  
Vol 23 (4) ◽  
pp. 1498-1505 ◽  
Author(s):  
Thomas A. Houpt ◽  
David W. Pittman ◽  
Jan M. Barranco ◽  
Erin H. Brooks ◽  
James C. Smith
Keyword(s):  
Magnetic Fields ◽  
High Strength ◽  
Behavioral Effects ◽  
Static Magnetic Fields

The anorectic effect of fenfluramine is influenced by sex and stage of the estrous cycle in rats

2005 ◽  
Vol 288 (6) ◽  
pp. R1486-R1491 ◽  
Author(s):  
Lisa A. Eckel ◽  
Heidi M. Rivera ◽  
Deann P. D. Atchley
Keyword(s):  
Food Intake ◽  
Estrous Cycle ◽  
Female Rats ◽  
Male Rats ◽  
Gonadal Hormone ◽  
Estrous Female ◽  
Male And Female Rats ◽  
Daily Food ◽  
Hormone Status ◽  
Anorectic Effect

The controls of food intake differ in male and female rats. Daily food intake is typically greater in male rats, relative to female rats, and a decrease in food intake, coincident with the estrous stage of the ovarian reproductive cycle, is well documented in female rats. This estrous-related decrease in food intake has been attributed to a transient increase in the female rat's sensitivity to satiety signals generated during feeding bouts. Here, we investigated whether sex or stage of the estrous cycle modulate the satiety signal generated by fenfluramine, a potent serotonin (5-HT) releasing agent. To examine this hypothesis, food intake was monitored in male, diestrous female, and estrous female rats after intraperitoneal injections of 0, 0.25, and 1.0 mg/kg d-fenfluramine. The lower dose of fenfluramine decreased food intake only in diestrous and estrous females, suggesting that the minimally effective anorectic dose of fenfluramine is lower in female rats, relative to male rats. Although the larger dose of fenfluramine decreased food intake in both sexes, the duration of anorexia was greater in diestrous and estrous female rats, relative to male rats. Moreover, the magnitude of the anorectic effect of the larger dose of fenfluramine was greatest in estrous rats, intermediate in diestrous rats, and least in male rats. Thus our findings indicate that the anorectic effect of fenfluramine is modulated by gonadal hormone status.

Sexual dimorphism in vasopressin-induced contraction of rat aorta

1991 ◽  
Vol 260 (2) ◽  
pp. H453-H458 ◽  
Author(s):  
J. N. Stallone ◽  
J. T. Crofton ◽  
L. Share
Keyword(s):  
Estrous Cycle ◽  
Vascular Reactivity ◽  
Rat Aorta ◽  
Isometric Tension ◽  
Female Rats ◽  
Male Rats ◽  
Maximal Response ◽  
Sprague Dawley ◽  
Tension Development ◽  
Sprague Dawley Rats

Previously, we reported that, in the rat, pressor responsiveness to vasopressin (VP) is higher in males than in females during most phases of the estrous cycle. To explore the role of the vasculature in this phenomenon, we examined vascular reactivity to VP in thoracic aortas of male rats and female rats during each phase of the estrous cycle. Aortic rings were prepared from age-matched male and female Sprague-Dawley rats and mounted for isometric tension recording. Maximal response of female aortas to VP (4,246 +/- 163 mg/mg ring dry wt) was more than twice (P less than 0.001) that of male aortas (1,877 +/- 215 mg/mg ring wt). Sensitivity of female aortas to VP was substantially higher (P less than 0.001) than that of male aortas (EC50: 10.9 +/- 0.7 vs. 19.0 +/- 1.6 nM, respectively). Maximal rate of tension development (dT/dtmax) during contraction with VP was nearly twofold higher (P less than 0.01) in female aortas (536 +/- 23 mg/min) than in male aortas (300 +/- 19 mg/min). Maximal response, sensitivity, and dT/dtmax of female aortas did not vary significantly during the estrous cycle. Maximal response of female aortas to phenylephrine (PE; 1,251 +/- 93 mg/mg ring wt) was half that (P less than 0.001) of male aortas (2,546 +/- 194 mg/mg ring wt); sensitivity to PE did not differ significantly (EC50: 0.33 +/- 0.02 vs. 0.38 +/- 0.06 microM, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)

scholarly journals A decade of magnetic vestibular stimulation: from serendipity to physics to the clinic

2019 ◽  
Vol 121 (6) ◽  
pp. 2013-2019 ◽  
Author(s):  
Bryan K. Ward ◽  
Dale C. Roberts ◽  
Jorge Otero-Millan ◽  
David S. Zee
Keyword(s):  
Magnetic Fields ◽  
Inner Ear ◽  
Lorentz Force ◽  
Semicircular Canals ◽  
High Strength ◽  
Ionic Currents ◽  
Vestibular Stimulation ◽  
Static Magnetic Fields ◽  
Magnetic Resonance Imaging Mri ◽  
Vestibular Asymmetry

For many years, people working near strong static magnetic fields of magnetic resonance imaging (MRI) machines have reported dizziness and sensations of vertigo. The discovery a decade ago that a sustained nystagmus can be observed in all humans with an intact labyrinth inside MRI machines led to a possible mechanism: a Lorentz force occurring in the labyrinth from the interactions of normal inner ear ionic currents and the strong static magnetic fields of the MRI machine. Inside an MRI, the Lorentz force acts to induce a constant deflection of the semicircular canal cupula of the superior and lateral semicircular canals. This inner ear stimulation creates a sensation of rotation, and a constant horizontal/torsional nystagmus that can only be observed when visual fixation is removed. Over time, the brain adapts to both the perception of rotation and the nystagmus, with the perception usually diminishing over a few minutes, and the nystagmus persisting at a reduced level for hours. This observation has led to discoveries about how the central vestibular mechanisms adapt to a constant vestibular asymmetry and is a useful model of set-point adaptation or how homeostasis is maintained in response to changes in the internal milieu or the external environment. We review what is known about the effects of stimulation of the vestibular system with high-strength magnetic fields and how the understanding of the mechanism has been refined since it was first proposed. We suggest future ways that magnetic vestibular stimulation might be used to understand vestibular disease and how it might be treated.

Effects on growth and body composition of androgen deprivation by castration or autoimmunization to LH-releasing hormone in the male rat under conditions of controlled food intake

1986 ◽  
Vol 110 (1) ◽  
pp. 97-102 ◽  
Author(s):  
J. M. Fletcher ◽  
G. E. Lobley ◽  
A. Connell
Keyword(s):  
Body Composition ◽  
Food Intake ◽  
Gonadal Hormones ◽  
Female Rats ◽  
Male Rats ◽  
Releasing Hormone ◽  
Energy Retention ◽  
Lh Releasing Hormone ◽  
Testicular Steroids ◽  
Intact Rats

ABSTRACT The effects of endogenous gonadal hormones on the regulation of body composition and energy retention have been investigated under conditions of controlled food intake. Male and female rats were fed the same amount from weaning to 82 days of age. The carcases of males contained more protein, less lipid and yielded more ash than females, but they had the same amount of total energy in their carcases as females. In a second experiment, male rats were sham-operated or castrated at 19 days and then fed equal amounts from weaning. At 40 days, intact and castrated rats did not differ in total carcase energy content nor in carcase composition. At 82 days the carcases of intact rats had more protein but had retained the same amount of energy as castrated rats. By 131 days, the difference in protein content was larger and intact rats had less carcase lipid, less carcase energy and gave less ash than castrated rats. At the same age and with a similar food intake, the differences in carcase composition between intact males and females were considerably larger than between intact and castrated males. In a third experiment, male rats were sham-operated or castrated at 1 day post partum and fed the same amount as in the second experiment from weaning to 82 days. Both sham-castrated and castrated rats grew less well than rats operated on at 19 days. The differences in carcase composition between intact and castrated rats were in the same direction but of greater magnitude than in rats operated at the later age. In a fourth experiment the effects on body compositon and energy retention of sham-operation, castration or immunization to LH-releasing hormone (LHRH) at weaning were compared in male rats fed the same amount from weaning to 131 days. Intact rats retained less carcase energy, less lipid and produced less ash than castrated and LHRH-immunized animals. Castrated and LHRH-immunized rats did not differ in carcase composition or amount of energy retained. It is concluded that (1) endogenous sex steroids affect growth and carcase composition independently of food intake, (2) the characteristic carcase composition of the female rat is largely due to the presence of ovarian steroids rather than lack of testicular steroids, (3) in the absence of increased food intake the effects of testicular steroids upon growth and energy expenditure are small but similar to those found in animals with free access to food, (4) the long-terms effects of perinatal exposure to testicular steroids upon growth and carcase composition are not only a consequence of changed food intake and (5) surgical castration and functional castration, induced by LHRH auto-immunization, produce the same effects on carcase composition. J. Endocr. (1986) 110, 97–102

scholarly journals Local Cerebral Glucose Utilization in Normal Female Rats: Variations during the Estrous Cycle and Comparison with Males

1985 ◽  
Vol 5 (3) ◽  
pp. 393-400 ◽  
Author(s):  
Astrid Nehlig ◽  
Linda J. Porrino ◽  
Alison M. Crane ◽  
Louis Sokoloff
Keyword(s):  
Estrous Cycle ◽  
Glucose Utilization ◽  
Brain Regions ◽  
Female Rats ◽  
Male Rats ◽  
Normal Male ◽  
Normal Female ◽  
Female Rat ◽  
Males And Females ◽  
The Brain

The quantitative 2-[14C]deoxyglucose autoradiographic method was used to study the fluctuations of energy metabolism in discrete brain regions of female rats during the estrous cycle. A consistent though statistically nonsignificant cyclic variation in average glucose utilization of the brain as a whole was observed. Highest levels of glucose utilization occurred during proestrus and metestrus, whereas lower rates were found during estrus and diestrus. Statistically significant fluctuations were found specifically in the hypothalamus and in some limbic structures. Rates of glucose utilization in the female rat brain were compared with rates in normal male rats. Statistically significant differences between males and females at any stage of the estrous cycle were confined mainly to hypothalamic areas known to be involved in the control of sexual behavior. Glucose utilization in males and females was not significantly different in most other cerebral structures.

scholarly journals Gender Differences in the Effect of Prenatal Methamphetamine Exposure and Challenge Dose of Other Drugs on Behavior of Adult Rats

2013 ◽  
pp. S99-S108 ◽  
Author(s):  
R. ŠLAMBEROVÁ ◽  
E. MACÚCHOVÁ ◽  
K. NOHEJLOVÁ-DEYKUN ◽  
B. SCHUTOVÁ ◽  
L. HRUBÁ ◽  
...  
Keyword(s):  
Estrous Cycle ◽  
Adult Male ◽  
Gonadal Hormones ◽  
Female Rats ◽  
Male Rats ◽  
Prenatally Exposed ◽  
Challenge Dose ◽  
Adult Rats ◽  
Male And Female ◽  
Male And Female Rats

The aim of the present study was to compare the response to acute application of several drugs in adult male and female rats prenatally exposed to methamphetamine (MA). Spontaneous locomotor activity and exploratory behavior of adult male and female rats prenatally exposed to MA (5 mg/kg) or saline were tested in a Laboras apparatus (Metris B.V., Netherlands) for 1 h. Challenge dose of the examined drug [amphetamine – 5 mg/kg; cocaine – 5mg/kg; MDMA (3,4-methylenedioxymethamphetamine) – 5 mg/kg; morphine – 5 mg/kg; THC (delta9-tetrahydrocannabinol) – 2 mg/kg] or saline was injected prior to testing. Our data demonstrate that prenatal MA exposure did not affect behavior in male rats with cocaine or morphine treatment, but increased locomotion and exploration in females. Application of amphetamine and MDMA in adulthood increased activity in both sexes, while cocaine and THC only in female rats. Morphine, on the other hand, decreased the activity in the Laboras test in both sexes. As far as sex and estrous cycle is concerned, the present study shows that males were generally less active than females and also females in proestrus-estrus phase of the estrous cycle were more active than females in diestrus. In conclusion, the present study shows that the prenatal MA exposure does not induce general sensitization but affects the sensitivity to drugs dependently to mechanism of drug action and with respect to gonadal hormones.

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 Changes in RFamide-Related Peptide-1 (RFRP-1)-Immunoreactivity During Postnatal Development and the Estrous Cycle

Endocrinology ◽  
2014 ◽  
Vol 155 (11) ◽  
pp. 4402-4410 ◽  
Author(s):  
Sara R. Jørgensen ◽  
Mille D. Andersen ◽  
Agnete Overgaard ◽  
Jens D. Mikkelsen
Keyword(s):  
Postnatal Development ◽  
Estrous Cycle ◽  
Third Ventricle ◽  
Female Rats ◽  
Male Rats ◽  
Relative Distribution ◽  
Gonadotropin Secretion ◽  
Related Peptide

Abstract GnRH is a key player in the hypothalamic control of gonadotropin secretion from the anterior pituitary gland. It has been shown that the mammalian counterpart of the avian gonadotropin inhibitory hormone named RFamide-related peptide (RFRP) is expressed in hypothalamic neurons that innervate and inhibit GnRH neurons. The RFRP precursor is processed into 2 mature peptides, RFRP-1 and RFRP-3. These are characterized by a conserved C-terminal motif RF-NH2 but display highly different N termini. Even though the 2 peptides are equally potent in vitro, little is known about their relative distribution and their distinct roles in vivo. In this study, we raised an antiserum selective for RFRP-1 and defined the distribution of RFRP-1-immunoreactive (ir) neurons in the rat brain. Next, we analyzed the level of RFRP-1-ir during postnatal development in males and females and investigated changes in RFRP-1-ir during the estrous cycle. RFRP-1-ir neurons were distributed along the third ventricle from the caudal part of the medial anterior hypothalamus throughout the medial tuberal hypothalamus and were localized in, but mostly in between, the dorsomedial hypothalamic, ventromedial hypothalamic, and arcuate nuclei. The number of RFRP-1-ir neurons and the density of cellular immunoreactivity were unchanged from juvenile to adulthood in male rats during the postnatal development. However, both parameters were significantly increased in female rats from peripuberty to adulthood, demonstrating prominent gender difference in the developmental control of RFRP-1 expression. The percentage of c-Fos-positive RFRP-1-ir neurons was significantly higher in diestrus as compared with proestrus and estrus. In conclusion, we found that adult females, as compared with males, have significantly more RFRP-1-ir per cell, and these cells are regulated during the estrous cycle.

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