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J D Blaustein

Publications and source records attributed to J D Blaustein.

At least 73 records · Page 4Linked to original sources
PubMed1991

Estrogen receptor binding in regions of the rat hypothalamus and preoptic area after inhibition of dopamine-beta-hydroxylase.

Previous studies have shown that administration of diethyldithiocarbamate (DDC), a dopamine-beta-hydroxylase inhibitor, results in a decreased concentration of estrogen receptors measured in the rodent hypothalamus and preoptic area. To determine if this modulation of receptor content is region-specific, in vitro estrogen binding assays were performed on cytosol and cell nuclear extracts of microdissected brain regions from female rats treated with DDC. For cytosol binding comparisons, ovariectomized (OVX) rats were treated with 550 mg DDC/kg b. wt. or the saline vehicle 12 h before sacrifice. For cell nuclear binding comparisons, OVX rats received a maximal dose of estradiol 12 h after DDC or saline treatment and 1 h before sacrifice. No region-specific decreases in estrogen binding were observed in either cytosol or nuclear extracts. To further examine possible regional specificity, quantitative autoradiographic analysis of the in vivo hypothalamic uptake of an iodinated analog of estradiol, 11 beta-methoxy-16 alpha-[125I]iodoestradiol (MIE2), in OVX rats treated with DDC was conducted. Animals received a saturating dose of [125I]MIE2 12 h after DDC or saline treatment and 1 h before sacrifice. DDC treatment resulted in higher background levels of radioactivity and a trend toward higher uptake levels in all brain regions, but with no evidence of marked regional specific effects in any area of the brain. In tissue uptake studies, DDC treatment resulted in higher levels of radioactivity recovered from serum and neural tissues of [125I]MIE2-injected rats, suggesting that DDC slows the clearance of MIE2.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

Development of estradiol-induced progestin receptor immunoreactivity in the hypothalamus of female guinea pigs.

The inability of young female guinea pigs to display progesterone-facilitated lordosis has been attributed, in part, to a deficiency in the concentration of hypothalamic estradiol-induced progestin receptors, as measured by in vitro binding assays. An immunocytochemical technique was used to ascertain where, within the mediobasal hypothalamus, estradiol-induced progestin receptor levels are lower in immature than in adult females. Adult (greater than 7 weeks) and juvenile (3 weeks) ovariectomized females received 10 micrograms estradiol benzoate, a dose that primes adult, but not immature females to respond behaviorally to progesterone. Progestin receptor-immunoreactive (PR-IR) cells were counted in the arcuate nucleus (ARC) and ventrolateral hypothalamus (VLH), the two regions containing the densest populations of estradiol-induced progestin receptors in the mediobasal hypothalamus. There was no age difference in the number of PR-IR cells in the rostral or caudal VLH, but immunostaining was darker in the rostral VLH of juveniles as compared to adults. We found similar numbers of PR-IR cells in the rostral and mid-ARC, but 35% fewer immunostained cells in the caudal ARC of immature, as compared to adult females. Furthermore, staining intensity was weaker in the mid- and caudal ARC of the juvenile females. These data suggest that the ARC, not the VLH, is a site of fewer estradiol-induced progestin receptors in immature females.

Aging↗
PubMed1991

Progesterone facilitates lordosis, but not LH release, in estradiol pulse-primed male rats.

Gonadectomized (GDX) male and female rats received repeated cycles of estradiol pulses, which prime animals of both sexes to display progesterone-facilitated lordosis. One, three and six treatment cycles of estradiol pulses followed by progesterone induced progressively higher luteinizing hormone (LH) surges in GDX females. Six treatment cycles of estradiol pulses alone (i.e., without subsequent progesterone treatment) induced a small but significant (approximately 4 ng/ml) increase in LH levels in GDX females. In contrast, GDX males never produced LH surges in response to estradiol pulses alone or estradiol pulses followed by progesterone, regardless of the number of hormone treatment cycles. Thus, female patterns of steroid-induced sexual receptivity and LH release are not inextricably linked, as steroid treatments sufficient for induction of lordosis do not stimulate LH secretion in adult male rats. These data also suggest that the neural system governing the LH surge might be more firmly sexually differentiated than that responsible for sexual receptivity in rats.

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PubMed1990

Many progestin receptor-containing neurons in the guinea pig ventrolateral hypothalamus contain substance P: immunocytochemical evidence.

Behavioral and neuroanatomical evidence in rats suggests that substance P may mediate hormonally induced sexual receptivity. To determine if progestin receptor-containing neurons in the guinea pig hypothalamus also contained substance P, we used a double antibody, immunocytochemical technique. Ovariectomized, adult guinea pigs were estradiol-primed for one week. Two days prior to perfusion, colchicine was infused into the lateral ventricle. Substance P-immunoreactive neurons and progestin receptor-immunoreactive neurons were found throughout the hypothalamus and caudal preoptic area. However, substance P and progestin receptor immunoreactivity occurred in the same neurons almost exclusively in the ventrolateral area of the hypothalamus, an important site in the hormonal regulation of female sexual behavior in guinea pigs. Within this area, approximately 35% of the progestin receptor-immunoreactive neurons also contained substance P immunoreactivity. These neuroanatomical data are consistent with the hypothesis that substance P may mediate some of the neural actions of progesterone.

Animals↗
PubMed1990

Down-regulation of progestin receptors in guinea pig brain: new findings using an immunocytochemical technique.

Progesterone injection in estradiol-primed, ovariectomized guinea pigs results in down-regulation of hypothalamic progestin receptors determined by in vitro binding assays. In order to determine if progesterone also decreases immunostaining of progestin receptors and if progestin receptors are down-regulated preferentially in particular neuroanatomical areas, ovariectomized guinea pigs were injected with doses of estradiol benzoate (10 micrograms at 42 h before progesterone injection) and progesterone (500 micrograms at 4, 12, or 24 h before perfusion) that reliably induce the expression of lordosis and subsequent behavioral refractoriness to progesterone. Progestin receptor-immunoreactive cells were counted in sections from discrete parts of the preoptic area and hypothalamus. As expected, estradiol dramatically increased cell nuclear, and, to a lesser extent, cytoplasmic, immunostaining in defined regions of the preoptic area and hypothalamus. By 12 h after progesterone injection, the number of progestin receptor-immunoreactive cells had decreased in some areas, but not others. The rostral and caudal aspects of the ventrolateral hypothalamus were particularly responsive showing a substantial decrease in progestin receptor-immunoreactivity by 12 h after injection. No decreases in the progestin receptor-immunoreactive cell number were observed in any of the preoptic regions examined, although obvious decreases in immunostaining intensity were seen. The results of these immunocytochemical experiments extend earlier findings from in vitro progestin binding experiments and demonstrate that as with progestin binding, progestin receptor-immunoreactivity decreases when progesterone is injected in a behavioral desensitization procedure. Furthermore, they point to the ventrolateral hypothalamus as one site in which the down-regulation of progestin receptors may be particularly responsive to progesterone.

Animals↗
PubMed1990

Immunocytochemical colocalization of progestin receptors and beta-endorphin or enkephalin in the hypothalamus of female guinea pigs.

Double-label immunocytochemistry was used to determine whether estradiol-induced progestin receptors and either beta-endorphin or leucine-enkephalin are colocalized in female guinea pig brain. Ovariectomized, adult guinea pigs were implanted with capsules containing estradiol-17 beta to induce high levels of progestin receptors, and injected intracerebroventricularly with colchicine to improve visualization of the opiate peptides. Sections through the hypothalamus and preoptic area were processed for progestin receptor, followed by beta-endorphin or leucine-enkephalin immunocytochemistry. As reported previously, high concentrations of progestin receptor-immunoreactive (PR-IR) cells were found in the preoptic area (medial and periventricular portions, medial preoptic nucleus) and hypothalamus (anterior hypothalamic and arcuate nuclei, ventrolateral area). Many beta-endorphin-IR cells contained PR-IR in the arcuate nucleus and its surroundings (33%) and in the dorsomedial area of the hypothalamus (64%). Scattered enkephalin-IR cells were found in the septal nucleus, medial and lateral preoptic area, bed nucleus of the stria terminalis, and the arcuate nucleus. The ventromedial nucleus of the hypothalamus and dorsolateral magnocellular nucleus, respectively, contained moderate and heavy concentrations of enkephalin-IR cells. Although some of these areas also contained PR-IR, enkephalin-IR was colocalized consistently with PR-IR only in a small number of cells in the arcuate nucleus and ventromedial/ventrolateral area of the hypothalamus. These data, taken together with earlier observations that virtually all cells containing estradiol-induced PR-IR also contain estrogen receptor-IR, provide neuroanatomical evidence that hypothalamic actions of progesterone and estradiol may be mediated by beta-endorphin and/or enkephalin.

Animals↗
PubMed1990

Effects of day length on sheep neuroendocrine estrogen and progestin receptors.

Gonadal steroid hormone receptors were studied in anterior pituitary, preoptic area, and hypothalamus of ovariectomized ewes. We established that systemic administration of estradiol benzoate elevates levels of nuclear estrogen receptor concentrations and results in the appearance of cytosolic progestin receptor the binding characteristics of which are comparable with that reported in rats and guinea pigs [0.1 nM Kd, binding site density (Bmax) of 111, 22, and 2 fmol/mg protein in pituitary, medial basal hypothalamus, and preoptic area, respectively]. Brain tissues also contained a second, low-affinity progestin binding site. To examine possible effects of photoperiod on neuroendocrine steroid receptors, two groups of sheep were exposed to artificial photoperiods. Ewes experienced alternating periods of long (LD 16:8) or short (LD 8:16) days for 290 days to induce breeding season or anestrous states. Animals were then ovariectomized and given steroid treatments designed to mimic a luteal phase followed by either follicular phase levels of estradiol or withdrawal of all exogenous hormones before determination of neuroendocrine steroid receptor concentrations. Despite the ability of long photoperiods to arrest ovarian cyclicity, magnify negative feedback actions of estradiol upon luteinizing hormone, and reduce the ability of estrogen to trigger behavioral estrus, photoperiod did not influence nuclear estrogen receptor concentrations or the induction of cytosolic progestin receptors in the pituitary, hypothalamus, or preoptic area.

Animals↗
PubMed1989

Estrogen receptor-immunostaining of neuronal cytoplasmic processes as well as cell nuclei in guinea pig brain.

We have recently developed an immunocytochemical technique for staining estrogen receptors in cell nuclei of some cells in the guinea pig brain. With optimization of this technique, we have now been successful in staining estrogen receptor-immunoreactivity in processes of many neurons in the guinea pig brain that also contain estrogen receptor-immunoreactive cell nuclei. While reaction product is visible in cell nuclei under a wide variety of conditions, neuronal processes are darkly immunostained only with modifications of the procedure optimized for maximum sensitivity, for example, the multiple-bridge immunocytochemical procedure. Omission of Triton X-100 and/or dimethylsulfoxide, usually used to increase penetration of the antibodies, had no effect on immunostaining in processes or cell nuclei, and immunostaining was apparent in both vibratome-cut and freezing microtome-cut sections. Injection of estradiol, but not progesterone, caused the total loss of cytoplasmic estrogen receptor-immunostaining, consistent with the idea that the cytoplasmic immunostaining, like the cell nuclear immunostaining is due to the presence of estrogen receptors. In all neuroanatomical regions containing estrogen receptor-immunoreactive cell nuclei, associated processes of some, but not all cells were also immunostained. However, in certain areas, such as the midbrain central gray and the preoptic area, cytoplasmic staining was particularly dark. The cellular characteristics that result in immunostaining in some estrogen receptor-immunoreactive cells, and not in others is under investigation.

Animals↗
PubMed1989

Development of progesterone-facilitated lordosis in female guinea pigs: relationship to neural estrogen and progestin receptors.

Ovariectomized (OVX), 20-day-old female guinea pigs did not exhibit lordosis following treatment with estradiol benzoate (EB) and progesterone. Behavioral responsiveness to EB and progesterone developed abruptly; by 30 days of age, responses typical of adult females (greater than 9 weeks of age) were observed. In vitro assays of neural steroid receptors were performed to test the hypothesis that a deficiency in the concentration of hypothalamic and/or preoptic area estrogen and/or progestin receptors contributes to the lack of progesterone-facilitated lordosis in juvenile (20-day-old) females. Assay of cytosol progestin receptors in the mediobasal hypothalamus (MBH) and preoptic area (POA) of immature and adult females 40 h after injection of EB confirmed a previous report that the concentration of estradiol-induced cytosol progestin receptors in the MBH of juvenile females was slightly lower than that observed in adults. Furthermore, MBH cell nuclear accumulation of progestin receptors after progesterone injection was markedly lower (i.e. 42%) in immature, as compared to adult females. The concentrations of cytosol estrogen receptors in the MBH and POA did not differ between immature and adult OVX guinea pigs. Also, cell nuclear estrogen receptor accumulation in the MBH after estradiol injection was comparable in immature and adult females. These data suggest that a deficiency in cell nuclear progestin receptor accumulation in the MBH may contribute to the absence of progesterone-facilitated lordosis in estradiol-primed, immature female guinea pigs. This age-related difference in cell nuclear progestin receptor accumulation may be due, in part, to reduced concentrations of estradiol-induced cytosol progestin receptors.(ABSTRACT TRUNCATED AT 250 WORDS)

Aging↗
PubMed1989

Long-term ovariectomy and hormone-induced sexual behavior, progestin receptors, and hypothalamic morphology in female rats.

Long-term ovariectomy reduces the ability of estradiol and progesterone treatment to induce sexual receptivity in female rats. Previous researchers suggested that this effect may be due to a decreased induction of neural progestin receptors by estradiol in the long-term ovariectomized rats. The present study was designed to replicate and extend this finding, and to search for neuroanatomical correlates by measuring the volume of the ventromedial nucleus (VMN) of the hypothalamus, a putative site of action of estradiol and progesterone for the induction of female sexual behavior. Long-term ovariectomy (5 to 6 weeks) as compared to short-term ovariectomy (1 week) reduced the ability of estradiol-17 beta and progesterone treatment to induce sexually receptive and proceptive behaviors. Consistent with previous reports, our data show that the reduced levels of cytosol progestin receptors after long-term ovariectomy and estradiol treatment are related to a reduced ability of estradiol to induce the receptors. Long-term ovariectomy did not affect the concentration of cytosol progestin receptors in the preoptic area, suggesting a neuroanatomical specificity to this effect. Contrary to our predictions, long-term ovariectomy did not affect the volume of the VMN. In fact, estradiol treatment, while blocking the effect of long-term ovariectomy on sexual behavior, decreased the volume of the VMN. Therefore, the measurement of the volume of the VMN is not a good predictor of the responsiveness to steroid hormone induction of sexual behavior.

Animals↗
PubMed1989

Development of steroid-induced lordosis in female guinea pigs: effects of different estradiol and progesterone treatments, clonidine, and early weaning.

The ability of developing ovariectomized (OVX) guinea pigs to display lordosis following a variety of steroid treatments which are behaviorally effective in adults was examined. Females OVX at 11 days of age did not display lordosis at 20 days of age, following treatment with several dose combinations of estradiol benzoate (EB, 10-50 micrograms) and progesterone (0.5-5 mg). By 30 days of age, 25% of the animals responded to EB plus progesterone, and by 40 days of age, adult-typical responses were observed. The developmental profile of responsiveness to steroids was not altered by varying the age at OVX, or by allowing pups to remain with a lactating mother. OVX females given estradiol (E2) implants did not exhibit progesterone-facilitated lordosis earlier than those treated with EB: however, the former group did show an unusually high incidence of progesterone-independent lordosis at 40 days of age. Twenty-day-old females also did not respond behaviorally to discrete pulses of E2 followed by progesterone, a treatment which was very effective in adults. Finally, lordosis was not facilitated in EB-primed, 20-day-old females by the alpha-noradrenergic agonist, clonidine, a treatment which was effective in adult females. These data illustrate a variety of conditions under which juvenile female guinea pigs do not exhibit steroid-induced lordosis. Since 20-day-old, EB-treated females also did not exhibit clonidine-facilitated lordosis, incomplete development of the central steroid-responsive and/or noradrenergic systems may contribute to the inability to display steroid-induced estrous behavior at this age.

Animals↗
PubMed1989

Estradiol-induced progestin receptor immunoreactivity is found only in estrogen receptor-immunoreactive cells in guinea pig brain.

A fluorescent immunocytochemical technique was developed to determine if cells in the guinea pig hypothalamus and preoptic area that contain estradiol-induced progestin receptors also contain estrogen receptors. With this technique little or no progestin receptor-immunoreactivity (PR-IR) was observed in the absence of estrogen treatment in ovariectomized guinea pigs. As has been reported previously, priming with estradiol caused a large increase in the concentration of PR-IR cells in discrete regions of the hypothalamus and preoptic area, primarily in the arcuate nucleus, ventrolateral area of the hypothalamus, periventricular preoptic area, medial preoptic nucleus, medial preoptic area, anterior hypothalamic nucleus and anterior hypothalamus. A range of lightly to intensely labeled estrogen receptor-immunoreactive (ER-IR) cells were observed in high concentration in each of these areas, as well as in some areas in which no PR-IR cells have been identified, such as the amygdala. PR-IR was only observed in cells that also had ER-IR. In some areas such as the ventrolateral hypothalamic area and arcuate nucleus, nearly all medium to highly-fluorescent ER-IR cells also contained estradiol-induced PR-IR, while in the amygdala no PR-IR was observed despite a high concentration of ER-IR cells. These results confirm the hypothesis that progestin receptors are produced in estrogen receptor-containing cells in the brain, and they suggest that these cells are the sites where estradiol and progesterone act to influence behavior and physiology.

Animals↗
PubMed1989

Differential regulation of progestin receptor immunoreactivity in the rabbit oviduct.

Cellular distribution of progestin receptor immunoreactivity (PR-IR) in paraffin-embedded rabbit oviduct tissue was determined using a monoclonal antibody and the indirect immunoperoxidase method. Ampullar and isthmic tissue from ovariectomized animals primed with 17 beta-estradiol or vehicle alone was examined. As expected, in the absence of estradiol, PR-IR was rarely observed in the ampulla. Estradiol treatment increased PR-IR in cell nuclei of the stroma and muscularis of the ampulla, but not of the epithelium. In contrast, PR-IR was seen in epithelial cell nuclei of the isthmus in the absence of estradiol. Surprisingly, while estradiol treatment increased PR-IR in cell nuclei of the stroma and muscularis of the isthmus, it decreased PR-IR in the epithelium. These results suggest for the first time a differential regulation of progestin receptors in the ampulla and isthmus of the oviduct. In particular, while estradiol treatment increased PR-IR in the stroma and muscularis and was without effect on PR-IR in the epithelium of the ampulla, it decreased PR-IR in the epithelium of the isthmus.

Animals↗
PubMed1988

Immunocytochemical localization of estrogen-induced progestin receptors in guinea pig brain.

By using a combination of monoclonal antibodies to progestin receptors and a double-bridge peroxidase-antiperoxidase technique, a sensitive immunocytochemical method was developed for visualizing progestin receptor immunoreactivity (PR-IR) in brains of estrogen-primed guinea pigs. PR-IR neurons were observed throughout the hypothalamus and preoptic area. They were seen in largest numbers in the arcuate nucleus, periventricular preoptic regions, medial preoptic nucleus, medial preoptic area and in the ventrolateral area of the hypothalamus. Lower numbers of PR-IR positive cells were detected in the bed nucleus of stria terminalis, paraventricular nucleus and lateral hypothalamus with scattered cells seen throughout the hypothalamus and preoptic area. The PR-IR was mostly intranuclear with lighter staining in neuronal processes. Electron microscopy confirmed the predominantly intranuclear localization and further demonstrated that the reaction product was dispersed throughout the nucleus, but not associated with the nucleolus. Few PR-IR cells were observed in the absence of estradiol priming, and the reaction product was much lighter than in the presence of estradiol. Progesterone injection was without apparent effect on intensity of the PR-IR.

Animals↗
PubMed1988

Steroids induce hypothalamic progestin receptors and facilitate female sexual behavior in neonatal rats.

This report provides the first evidence that two activational actions of estrogen can occur within the first week of life in the rat. Priming 4-day-old rats with exogenous estradiol benzoate facilitates lordosis and ear wiggling-like behavior, and induces cytosol progestin receptors in the medial basal hypothalamus and preoptic region (Hyp-PoA) 44 h later. Moreover, unprimed male infants show more intense lordosis and higher concentrations of cytosol progestin receptors in Hyp-PoA than infant females. Neonatal castration of male infants decreases their concentration of cytosol progestin receptors in Hyp-PoA to the levels normally seen in infant females. In addition, priming 6-day-old infants with progesterone alone facilitates lordosis in male but not female infants. Together, these data demonstrate that in the male infant, endogenous steroids of testicular origin have activational as well as organizational actions.

Animals↗
PubMed1988

Progesterone facilitation of lordosis in male and female Sprague-Dawley rats following priming with estradiol pulses.

Adult male Sprague-Dawley rats rarely exhibit progesterone-facilitated lordosis following steroid treatments which are effective in females. In contrast, progesterone-facilitated lordosis has been observed following priming with estradiol pulses in another strain. The aim of this study was to compare progesterone-facilitated feminine sexual behavior in adult male and female Sprague-Dawley rats following priming with estradiol benzoate (EB) or estradiol pulses. Female sexual behavior was measured in adult, gonadectomized males and females treated as follows: Two pulses of estradiol followed by progesterone or oil the next day; EB (two doses) for 3 days, and progesterone or oil the next day. These protocols were repeated at 4- or 6-day intervals, respectively. Progesterone-facilitated lordosis was observed consistently in both sexes treated with estradiol pulses. By the fifth test, lordosis quotients did not differ between the sexes, but the lordosis ratings in progesterone-treated males remained lower than those observed in females. Proceptivity (hop-darting) was facilitated by progesterone in females, but was never observed in males. Lordosis was induced in both sexes by 15 micrograms EB, but was not reliably facilitated by progesterone. Treatment with the lower dose of EB (1.5 micrograms) induced high levels of receptivity in females (occasionally facilitated by progesterone), but not in males regardless of subsequent treatment (i.e, progesterone or oil). These data suggest that progesterone-facilitated lordosis can be induced in male Sprague-Dawley rats, if a regimen of estradiol pulses is used. Thus, the brain of the adult male is not inflexibly differentiated with regard to progesterone facilitation of feminine receptive behavior.

Animals↗
PubMed1987

Further evidence of noradrenergic regulation of rat hypothalamic estrogen receptor concentration: possible non-functional increase and functional decrease.

The regulation of estrogen receptors by the alpha 2-noradrenergic system was studied. A single injection of the alpha 2-noradrenergic antagonist, yohimbine, caused a biphasic effect on the concentration of cytosol estrogen receptors in the mediobasal hypothalamus and anterior pituitary gland. A short-latency increase was seen at 1.5-3 h, followed by a longer-lasting decrease at 8-16 h. Scatchard analysis revealed that the apparent, short-latency increase is in the concentration of binding sites, not in the affinity of the receptor for [3H]estradiol. The increase in the concentration of cytosol estrogen receptors is not blocked by pretreatment with the alpha 2-noradrenergic agonist, clonidine. In addition, no increase is detected in the concentration of cell nuclear estrogen receptors accumulating in response to a saturating dose of estradiol. Therefore, the apparent increase in the concentration of cytosol estrogen receptors may not represent a functional increase in receptors. The decrease in the concentration of estrogen receptors, which occurs 8-16 h after yohimbine treatment, is also seen after injection of the alpha 2-adrenergic antagonist, idazoxan, and is not due to a change in the in vitro rate of association of the receptors with [3H]estradiol. Furthermore, the decrease seems to be a functional decrease in the concentration of receptors capable of cell nuclear accumulation in response to estradiol injection, as indicated by the results of experiments in which the concentration of cell nuclear estrogen receptors was assayed after estradiol injection. These experiments provide further support for the hypothesis that the alpha-noradrenergic system, and perhaps specifically the alpha 2-subtype, is involved in decreasing the concentration of estrogen receptors in parts of the brain and pituitary gland. This interaction provides a mechanism by which the environment could regulate the sensitivity of certain neurons to estradiol. However, the finding that the initial increase in the concentration of cytosol estrogen receptors after yohimbine treatment is not followed by the predicted increase in cell nuclear estrogen receptors after estradiol injection raises questions about the physiological relevance of the apparent increase under some conditions.

Adrenergic alpha-Agonists↗