Numbers of neurons and astroglial cells in the suprachiasmatic nucleus of male and female rats

Güldner, F.-H.

doi:10.1007/bf00239203

Cited by 63 publications

(46 citation statements)

References 10 publications

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“…Our absolute estimate of SCN volume in males (0.060 mm 3 per side) is similar to that of Guldner (1983), who reported a unilateral SCN volume of 0.064 mm 3 . Robinson et al (1986) and Gorski et al (1978) also reported sex differences in volume of SCN, consistent with the present results.…”

Section: Discussionsupporting

confidence: 81%

Partial demasculinization of several brain regions in adult male (XY) rats with a dysfunctional androgen receptor gene

et al. 2005

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The adult rat posterodorsal medial amygdala (MePD) is sexually dimorphic in regional volume and neuronal soma size, both of which are larger in males than in females. This sexual dimorphism is entirely dependent on adult circulating levels of testicular androgens, and both androgen and estrogen treatment can masculinize MePD structure. We examined male rats that are rendered androgen-insensitive by the testicular feminization mutation (tfm) of the androgen receptor (AR) gene to determine how a dysfunctional AR affects this and other brain sexual dimorphisms. In adult wild-type rats, the MePD in males had a greater regional volume, rostrocaudal extent, and soma size than in females. In genetic males, defective ARs affected some but not all of these indices: MePD volume and soma size in tfm males were intermediate between those of wild-type males and females, but the rostrocaudal extent of the MePD was unaffected by the mutation, being as great in tfm males as in wild-type males. Regional volume and soma size in the suprachiasmatic nucleus was reduced in tfm males compared with wild-type males, suggesting that AR normally affects this region in male rats. Interestingly, whereas volume of the sexually dimorphic nucleus of the preoptic area was unaffected by the tfm allele, soma size in this region was reduced in tfm males compared with wild-type males. Although estrogen receptor activation has been shown to be vital for masculinization of the rodent brain, our results indicate that ARs also contribute to this process in several brain regions.

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Section: Discussionsupporting

confidence: 81%

Partial demasculinization of several brain regions in adult male (XY) rats with a dysfunctional androgen receptor gene

et al. 2005

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“…After treatment with identical doses of testosterone propionate, males have higher AR expression than do females (116), suggesting sexually dimorphic development of this system. This is consistent with findings of sex differences in SCN morphology in human (94,95) and rat (96)(97)(98) and in some aspects of circadian timing as well as the sensitivity of the circadian system to gonadal hormones (99)(100)(101). Sexually differentiated sleep patterns that appear at puberty and disappear in old age, presumably involving the circadian system, have also been reported (102).…”

Section: Testicular Hormones and Circadian Behaviorsupporting

confidence: 89%

Minireview: The Neuroendocrinology of the Suprachiasmatic Nucleus as a Conductor of Body Time in Mammals

Karatsoreos

Silver

2007

Endocrinology

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Circadian rhythms in physiology and behavior are regulated by a master clock resident in the suprachiasmatic nucleus (SCN) of the hypothalamus, and dysfunctions in the circadian system can lead to serious health effects. This paper reviews the organization of the SCN as the brain clock, how it regulates gonadal hormone secretion, and how androgens modulate aspects of circadian behavior known to be regulated by the SCN. We show that androgen receptors are restricted to a core SCN region that receives photic input as well as afferents from arousal systems in the brain. We suggest that androgens modulate circadian behavior directly via actions on the SCN and that both androgens and estrogens modulate circadian rhythms through an indirect route, by affecting overall activity and arousal levels. Thus, this system has multiple levels of regulation; the SCN regulates circadian rhythms in gonadal hormone secretion, and hormones feed back to influence SCN functions.For optimal function, organisms and cells must locate and operate in a defined temporal and spatial niche. The need for resource partitioning is obvious in the spatial domain and is also important in the temporal domain. The daily rising and setting of the sun provides a predictable environmental time cue to which organisms are sensitive. In mammals, a master circadian clock located in the suprachiasmatic nucleus (SCN) ensures that peripheral clocks throughout the brain and body function in the appropriate phase. Entrainment (synchronization to the environment) in mammalian systems involves the resetting of this master clock, which then communicates timing information to the rest of the body. In the absence of environmental cues, the internal clock runs at its endogenous, free-running period. This system permits the prediction of environmental changes while maintaining plastic responses to changes in the environment. SCN as Brain ClockEvidence that the SCN is the locus of a master circadian clock in mammals has been gathered over many years from many labs and entails methodologically distinct experimental paradigms with converging lines of evidence (1, 2). Briefly, lesions of the SCN result in a loss of all circadian rhythmicity in behavior and physiology, including hormone secretion. The SCN expresses rhythmic electrical and metabolic activity, even when placed in a dish in isolation from the rest of the brain (3, 4). After creation of a hypothalamic island containing the SCN, rhythmic electrical activity continues within the island (5), and hamsters bearing such hypothalamic islands continue to show rhythmic locomotor activity although the gonadal regression response to long-term constant darkness is lost (6). Transplantation of fetal hypothalamic tissue containing the SCN into the third ventricle of an SCN-lesioned animal restores circadian locomotor rhythms with a period reflecting that of the donor animal, but again, the gonadal regression response to constant darkness is lost (7,8). Interestingly, rhythms in hormone secretion are not restored by ...

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“…In Brown Norway rats (Roozendaal et al, 19871, the numbers of cells are greater than the numbers we estimated, contrary to the numbers found in Fischer rats (van den Pol, 19801, which are smaller. For Sprague-Dawley rats, some authors reported greater numbers than ours (PaulaBarbosa et al, 19901, whereas others found exactly the opposite (Guldner, 1983;Moore and Speh, 1993;Woods et al, 1993). The only estimation performed in the same strain as that used in this study was carried out by Nagai et al (19921, and the numbers found were smaller than those estimated in this report.…”

Section: Stereological Considerationscontrasting

confidence: 83%

Age and sex do not affect the volume, cell numbers, or cell size of the suprachiasmatic nucleus of the rat: An unbiased stereological study

Madeira¹,

Sousa²,

Santer

et al. 1995

J of Comparative Neurology

121

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The circadian rhythms displayed by numerous biological functions are known to be sex specific and affected by aging. It has not been settled yet whether the sex- and age-related characteristics of circadian rhythms derive from changes in the anatomy of the suprachiasmatic nucleus. To shed light on these issues, we applied unbiased stereological techniques to estimate the volume of the suprachiasmatic nucleus as well as the total number of its cells and the mean volume of their somata and nuclei in progressively older groups of male and female Wistar rats (aged 1, 6, 12, 18, 24, and 30 months). The volume of the nucleus was estimated with the Cavalieri principle on serial sections. The total numbers of neurons and astrocytes were estimated by applying the optical fractionator, and the mean somatic and nuclear volumes of cells were estimated by using isotropic, uniform random sections and the nucleator method. On average, the volume of the suprachiasmatic nucleus was 0.044 mm3, and the total number of neurons and astrocytes was 17,400. Cells of the dorsomedial and ventrolateral components of the nucleus, which are morphologically different, have identical mean perikaryal and nuclear volumes, which we estimated to be 750 microns3 and 400 microns3, respectively. We further demonstrated that, at all ages analysed, the volume of the suprachiasmatic nucleus, the total cell number, and the mean somatic and nuclear volumes of its cells are affected neither by the age nor by the sex of the animal, regardless of the presence of sex- and age-related variations in circadian rhythms. However, the possibility that females may display changes in the volume of the suprachiasmatic nucleus at older ages cannot be ruled out. No effect of aging was observed in the total number of neurons or in the total number of astrocytes.

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Numbers of neurons and astroglial cells in the suprachiasmatic nucleus of male and female rats

Cited by 63 publications

References 10 publications

Partial demasculinization of several brain regions in adult male (XY) rats with a dysfunctional androgen receptor gene

Partial demasculinization of several brain regions in adult male (XY) rats with a dysfunctional androgen receptor gene

Minireview: The Neuroendocrinology of the Suprachiasmatic Nucleus as a Conductor of Body Time in Mammals

Age and sex do not affect the volume, cell numbers, or cell size of the suprachiasmatic nucleus of the rat: An unbiased stereological study

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