Effect of Sex, Intrauterine Position and Androgen Manipulation on the Development of Brain Aromatase Activity in Fetal Ferrets

Krohmer, Randolph W.; Baum, Michael J.

doi:10.1111/j.1365-2826.1989.tb00114.x

Cited by 43 publications

(34 citation statements)

References 36 publications

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“…An obvious possibility is that in males exposure to testicular androgen over a prolonged prenatal and/or immediate postparturient period sensitizes the developing brain to respond to the relatively slight increments in circulating testosterone that occur neonatally in this species, as in other species including the rat (14). The results of a recent study (39) support such a conclusion.…”

Section: Developmental Effects Of Oestrogen and Androgensupporting

confidence: 79%

“…Evidence presented earlier in this review showed that the availability of androgenic substrate to the neural aromatizing enzymes is consistently greater in male than in female ferrets throughout the last quarter of gestation, when the steroids act to organize the Mn-POA/AH. Experimental manipulations of androgen receptor activation (either blockade via transplacental administration of the anti-androgen, flutamide, or activation via transplacental DHT) failed to influence the level of aromatase activity in POA + hypothalamus or temporal lobes of foetal ferrets (14). This finding implies that the increased level of oestrogen biosynthesis which apparently occurs in the male ferret's POA/AH must result from increased availability of androgenic substrate in foetuses of this sex, as opposed to an androgendependent activation of the aromatase enzyme such as occurs in the adult mammalian nervous system (102).…”

Section: Tonic Pulsatile Lh Secretionmentioning

confidence: 99%

“…In ferrets testicular steroidogenesis begins on or about embryonic Day 24 (E24) of a 41-day gestation (14, IS). Measurements of whole body androgen content, conducted after removal of the gonads in ferrets taken by caesarean section between Days E26 and E34 (14), showed that whole body androgen content was significantly higher in males than in females at all ages ( Fig. 1).…”

Section: Perinatal Profile Of Androgen Secretion In Ferretsmentioning

confidence: 99%

“…Foetal POA/AH and temporal lobe tissues are capable of aromatizing androgenic substrates as early as Day E26, shortly after the onset of testicular steroidogenesis in the male ferret, and the level of aromatase activity increases across the last quarter of gestation and persists before declining again after the seventh postnatal week (14,42). Oestradiol and androgen receptors have been isolated from ferret POA/AH on Day E36 (101); it seems likely that they exist at even earlier ages.…”

Section: Tonic Pulsatile Lh Secretionmentioning

confidence: 99%

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Steroidal Control of Behavioural, Neuroendocrine and Brain Sexual Differentiation: Studies in a Carnivore, the Ferret

Baum

Carroll

Cherrv

et al. 1990

J Neuroendocrinology

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More than 30 years have passed since the publication ( I ) showing that transplacental administration of testosterone to female guinea-pigs caused permanent changes in their ability to exhibit reproductive behaviours in response to ovarian steroids in adulthood. Over the intervening years articles have appeared which have extended this type of observation to numerous other mammalian species, including rat, hamster, gerbil, mouse, dog, ferret, pig, sheep, rhesus monkey, and marmoset (2, 3). In many instances inferences have been made about the probable existence of steroid-induced changes in the structure and function of the nervous system which underlie these changes in behaviour. These so-called 'organizational' effects of perinatal steroid exposure on the developing nervous system are often distinguished from the later 'activational' effects of these same steroids on the expression of sociosexual behaviours in adulthood. The number of different mammalian species used for mechanistic studies on the organizational effects of steroids, such as determining the precise perinatal timing of hormone action, the identity of the steroid(s) responsible for behavioural sexual differentiation, and the neural sites of steroid action, has been relatively small, and generally restricted to rodents. In the late 1970's sex steroids acting during development were first implicated in the differentiation of sexually dimorphic telencephalic structures in passerine song birds which control singing associated with courtship (4, 5). Since this early work, numerous studies have exploited the canary and zebra finch to explore mechanisms of steroid action in controlling the ontogeny of song in the male and the underlying changes in the nervous system. Other studies using the rat have explored in detail the role of androgen and oestrogen in controlling the differentiation in males of patterns of reproductive behaviour (2) as well as aspects of neural sex dimorphisms in the preoptic area/anterior hypothalamus (POA/AH) (6) and in the lumbar spinal cord (7). The concentration of mechanistic (behavioural, biochemical, neuroanatomical) studies of steroidal effects on sexually dimorphic behavioural potential in a few avian and rodent species is understandable, in light of their relative availability, low expense, and rapid time-course of neural development.Despite the substantial progress already made using these lower vertebrate models in promoting our understanding of how sex steroids influence neural and behavioural development, extrapolation of the results obtained in these studies to higher mammals including man cannot occur in the absence of some degree of empirical verification. Obviously, experimental manipulations of steroidal exposure during the development of human subjects would be unethical, thus we are left with experiments of nature (e.g. congenital adreno-genital syndrome,androgen insensitivity syndrome, and Sa-reductase deficient pseudohermaphroditism; details in later sections) with which to ask questions about the role of sex...

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Section: Developmental Effects Of Oestrogen and Androgensupporting

confidence: 79%

Section: Tonic Pulsatile Lh Secretionmentioning

confidence: 99%

Section: Perinatal Profile Of Androgen Secretion In Ferretsmentioning

confidence: 99%

Section: Tonic Pulsatile Lh Secretionmentioning

confidence: 99%

See 2 more Smart Citations

Steroidal Control of Behavioural, Neuroendocrine and Brain Sexual Differentiation: Studies in a Carnivore, the Ferret

Baum

Carroll

Cherrv

et al. 1990

J Neuroendocrinology

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“…There are sex differences in exposures to androgens and estrogens that appear to underlie normal reproductive neuroendocrine development [85,164,146]. Aberrations in these developmental patterns in females can cause masculinization (acquisition of a male-typical trait) or defeminization (loss of a female-typical trait), and in males, may cause feminization or demasculinization (comparably defined).…”

Section: Introduction To Development Of Reproductive Neuroendocrine Cmentioning

confidence: 99%

Developmental programming and endocrine disruptor effects on reproductive neuroendocrine systems

Gore¹

2008

Frontiers in Neuroendocrinology

231

122

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The ability of a species to reproduce successfully requires the careful orchestration of developmental processes during critical time points, particularly the late embryonic and early postnatal periods. This article begins with a brief presentation of the evidence for how gonadal steroid hormones exert these imprinting effects upon the morphology of sexually differentiated hypothalamic brain regions, the mechanisms underlying these effects, and their implications in adulthood. Then, I review the evidence that aberrant exposure to hormonally-active substances such as exogenous endocrine-disrupting chemicals (EDCs), may result in improper hypothalamic programming, thereby decreasing reproductive success in adulthood. The field of endocrine disruption has shed new light on the discipline of basic reproductive neuroendocrinology through studies on how early life exposures to EDCs may alter gene expression via non-genomic, epigenetic mechanisms, including DNA methylation and histone acetylation. Importantly, these effects may be transmitted to future generations if the germline is affected via transgenerational, epigenetic actions. By understanding the mechanisms by which natural hormones and xenobiotics affect reproductive neuroendocrine systems, we will gain a better understanding of normal developmental processes, as well as to develop the potential ability to intervene when development is disrupted.

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Sex difference and steroidal stimulation of galanin immunoreactivity in the ferret's dorsal preoptic area/anterior hypothalamus

1997

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A sexually dimorphic male nucleus (MN) is seen in Nissl-stained sections from the dorsal preoptic area/anterior hypothalamus (dPOA/AH) of male, but not female, ferrets. We used immunohistochemical methods to determine whether particular neuropeptides are found in cells of the MN. A sexually dimorphic cluster of galanin-immunoreactive (IR) cells was found in the dPOA/AH of ferrets killed either on embryonic day (E) 38 or in adulthood. Significantly more galanin-IR cells were distributed in the MN and in other subregions of the dPOA/AH of intact breeding males than estrous females. The density of galanin-IR cells in the dPOA/AH was significantly reduced in adult males by castration and restored to the level of intact breeding males by daily injections of testosterone propionate (TP) for 5 weeks. The same TP treatment failed to augment the density of galanin-IR cells in the dPOA/AH of adult, ovariectomized females. Computer-assisted image analysis and grid-crossing analysis showed that the area and the number of galanin-IR fibers in the dPOA/AH were significantly greater in adult females than in males, regardless of subjects' concurrent steroidal condition. A cluster of galanin-IR cells was present in the dPOA/AH of males, but not females, killed on either E34 or E38. Administration of TP between E28 and E37 significantly increased the density of galanin-IR cells in the dPOA/AH of females killed on E38, up to the level seen in control males. The results suggest that the capacity of cells located in the dPOA/AH to express galanin after adult steroid exposure is sexually differentiated by the fetal action of testosterone, or its metabolite, estradiol, in males.

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Effect of Sex, Intrauterine Position and Androgen Manipulation on the Development of Brain Aromatase Activity in Fetal Ferrets

Cited by 43 publications

References 36 publications

Steroidal Control of Behavioural, Neuroendocrine and Brain Sexual Differentiation: Studies in a Carnivore, the Ferret

Steroidal Control of Behavioural, Neuroendocrine and Brain Sexual Differentiation: Studies in a Carnivore, the Ferret

Developmental programming and endocrine disruptor effects on reproductive neuroendocrine systems

Sex difference and steroidal stimulation of galanin immunoreactivity in the ferret's dorsal preoptic area/anterior hypothalamus

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