Estrogen Receptor Messenger Ribonucleic Acid Research Articles

Tumor-specific expression of alternatively spliced estrogen receptor messenger ribonucleic acid variants in human pituitary adenomas.

The well documented mitogenic and hormone regulatory effects of estrogen (E2) on pituitary cells are mediated via its nuclear receptor (ER), a cellular homolog of v-erbA oncogene. ER isoforms generated by alternative exon splicing, termed ER variants delta 2ER to delta 7ER, have been identified in breast cancer and have been postulated to have important pathogenetic and clinical implications in tumorigenesis and/or development of hormone resistance. Because pituitary tumors, particularly prolactinomas, are known to be E2-dependent, we investigated alternatively spliced ER variant messenger ribonucleic acid expression in 40 human pituitary tumors of various phenotypes and normal pituitary tissues, using reverse transcription-PCR and Southern blot analyses. Nine of 11 prolactinomas readily expressed multiple ER variants (delta 2ER, delta 4ER, 5ER, and delta 7ER), whereas 6 of 11 tumors showed faint expression of delta 3ER. Four of 7 glycoprotein hormone-producing tumors that synthesized FSH beta expressed delta 2ER, delta 5ER, and delta 7ER. In 9 GH- and 10 ACTH-secreting tumors examined, the expression of normal and variant ER was restricted to tumors that also exhibited scattered PRL immunoreactivity. Variant and normal ER were not found in three null cell tumors (oncocytomas) that showed negative immunoreactivity for all pituitary hormones or their subunits. In contrast, only delta 4ER and delta 7ER were uniformly detected in normal pituitaries. delta 6ER was not detected in any normal or neoplastic pituitary specimen studied. We conclude that multiple alternatively spliced ER variants are coexpressed with normal ER in a tumor phenotype-specific manner. In addition, ER variants delta 2ER and delta 5ER were found to be tumor specific. Future functional studies will be required to determine whether coexpression of multiple ER variants along with normal ER confers a pathophysiological role in pituitary hormone regulation and/or tumor cell proliferation.

Tumor-Specific Expression of Alternatively Spliced Estrogen Receptor Messenger Ribonucleic Acid Variants in Human Pituitary Adenomas

Tumor-Specific Expression of Alternatively Spliced Estrogen Receptor Messenger Ribonucleic Acid Variants in Human Pituitary Adenomas

Hormone receptors in vestibular schwannomas.

The possibility that steroid hormones play a role in vestibular schwannoma proliferation has been suggested by a number of investigators. There is conflicting information about the presence of steroid hormone receptors in these tumors. The aim of this study was to examine the expression of androgen, progesterone, glucocorticoid and estrogen receptor messenger ribonucleic acid levels (mRNA) in twenty-one vestibular schwannomas by either Northern blot analysis or the polymerase chain reaction (PCR). Glucocorticoid receptor mRNA was expressed in all twenty-one tumors examined. Only two male specimens were positive for androgen receptor mRNA expression by PCR-Southern blot analysis. Thirty-three percent of the schwannomas (7/21) showed a strong band for progesterone receptor mRNA by PCR-Southern blot analysis; there were an equal number of males and females in this group. Estrogen receptor mRNA levels were undetectable in all tumors examined by PCR-Southern blot analysis. These studies suggest that the pattern of steroid receptor expression is different in schwannomas than in meningiomas. Individual vestibular schwannomas need to be examined for their steroid receptor mRNA expression mRNA expression to know whether they will be responsive.

Steroid regulation of estrogen and progestin receptor messenger ribonucleic acid in monkey hypothalamus and pituitary

Steroid regulation of estrogen and progestin receptor messenger ribonucleic acid in monkey hypothalamus and pituitary

Steroid regulation of estrogen and progestin receptor messenger ribonucleic acid in monkey hypothalamus and pituitary.

The regulation of estrogen and progestin receptor (ER and PR, respectively) messenger RNA (mRNA) and protein by their cognate hormones was examined in the hypothalamus and pituitary of steroid-treated monkeys. Rhesus macaques (Macaca mulatta) were ovariectomized, hysterectomized (spayed), and implanted with SILASTIC brand capsules containing 17 beta-estradiol (E) or progesterone (P). The spayed control group received empty capsules. The E-treated group received E-filled capsules for 28 days. The E + P-treated animals received an E-filled capsule for 28 days and then a P-filled capsule for the last 14 of the 28 days. Steroid regulation of ER and PR mRNA levels in the hypothalamus and pituitary was examined with in situ hybridization. In the hypothalamus, ER and PR immunodetectable proteins were also examined in nearby sections. In the pituitary, mRNA levels were compared to previous ER and PR protein analysis of identically treated animals. E treatment induced PR mRNA in the medial basal hypothalamus and pituitary. Supplemental P treatment had no effect on PR mRNA levels in the hypothalamus, but markedly reduced PR mRNA in the pituitary. There was excellent agreement with PR protein detection by immunocytochemistry. E treatment had no effect on ER mRNA in the hypothalamus or pituitary. Supplemental P treatment decreased ER mRNA in the ventromedial nucleus, but not in the arcuate nucleus or pituitary. There was agreement between ER mRNA and ER protein in these areas. In summary, there is cell-specific regulation of PR by P in the hypothalamus and pituitary, where P down-regulates PR in the pituitary without affecting ER. However, P has no significant effect on PR expression in the hypothalamus even though P decreases ER in the ventromedial nucleus. Although these observations suggest diverse cell-specific regulatory mechanisms, they are consistent with ER- and PR-mediated physiological events, such as PRL secretion and sexual behavior.

Effect of gonadotropin-releasing hormone on estrogen receptor messenger ribonucleic acid level in perifused pituitary cells.

1. We examined the potential effect of GnRH pulses on pituitary estrogen receptor mRNA level. 2. The treatment of perifused pituitary cell aggregates with four hourly pulses of GnRH (10nM/1 min/h) resulted in a marked increase in the steady-state level of ER mRNA (25% vs unstimulated control, n = 3). 3. No changes were observed for the LH beta mRNA. Data suggest, for the first time, that a cross-talk between the GnRH and nuclear ER may occur in the gonadotrope cells.

Progesterone Inhibits Female-Typical Receptive Behavior and Decreases Hypothalamic Estrogen and Progesterone Receptor Messenger Ribonucleic Acid Levels in Whiptail Lizards (GenusCnemidophorus)

Female-typical sexual behavior in tetrapods is mediated primarily by estrogen and progesterone acting through intracellular receptors at specific sites in the mediobasal hypothalamus. Progesterone exerts both faciliatory and inhibitory actions on female sexual behavior and in well-studied rodent models, the inhibitory actions are exerted through downregulation of progesterone and estrogen receptors. This study examined progesterone effects on both female-typical sexual behavior and hypothalamic estrogen and progesterone receptor mRNA expression (ER- and PR-mRNA) in a sexual and parthenogenetic species of whiptail lizard. Progesterone capsules administered to ovariectomized femaleCnemidophorus inornatusandCnemidophorus uniparensfollowing a receptivity-inducing dosage of estradiol benzoate (EB) strongly inhibited receptive behavior as compared to blank implanted controls. Progesterone capsules administered either before or after an EB injection also strongly downregulated ER- and PR-mRNA abundance in the ventromedial nucleus of the hypothalamus relative to blank implanted controls. The correlated decrease in both EB-induced receptive behavior and ER- and PR-mRNAs following progesterone administration are similar to findings in rats and guinea pigs, suggesting that this is an evolutionarily conserved mechanism in the regulation of female sexual behavior.

Effects of glucocorticoids on estrogen receptor messenger ribonucleic acid in the pregnant ovine myometrium in vivo and in vitro.

We recently reported that estrogen receptor (ER) mRNA is dramatically increased in the sheep myometrium during cortisol-induced premature labor and term spontaneous labor. In this study, we compared myometrial ER mRNA and ER protein levels in tissues from pregnant sheep during infusions of two different glucocorticoids (dexamethasone and betamethasone). Tissues from glucocorticoid-infused sheep not yet in labor were compared with tissues from sheep in labor. The population of ER mRNA-containing cells in myometrium obtained from sheep in labor was determined by in situ hybridization and compared with that of sheep not in labor in order to understand how the cellular distribution of ER mRNA changed during labor. Finally, in vitro myometrial cell culture and immunolocalization of glucocorticoid receptor (GR) were used to determine 1) the effects of different steroids on ER mRNA content, 2) whether or not the myometrium is a functional site for glucocorticoid action, and 3) whether the change in ER mRNA content in the myometrium might be induced by glucocorticoid acting through GR. Increased ER mRNA and protein were found only in the myometrium associated with labor. In situ hybridization of ER mRNA and immunolocalization of ER protein showed that ER mRNA and protein were mainly located in the smooth muscle cells and endothelial cells of blood vessels. In vitro treatment of cultured myometrial cells with hydrocortisone resulted in a 3.5-fold increment in ER mRNA. In contrast, there was no obvious change in ER mRNA when myometrial cells were treated in vitro with either estradiol (10 nM) or progesterone (100 nM) for 24 h. GR was localized exclusively in the pregnant sheep myometrium. We conclude that 1) increased ER protein and ER mRNA in sheep myometrium are strongly associated with labor; 2) an increase in the population of ER-positive cells is associated with the increment of ER mRNA during glucocorticoid-induced labor; 3) in the pregnant sheep myometrium, both the smooth muscle cells and endothelial cells of blood vessels are positive for ER protein ER mRNA; and 4) hydrocortisone is a potent stimulus in vitro for increasing ER mRNA content, presumably acting through the GR present in the pregnant sheep myometrium.

Cell-specific expression of estrogen receptor in the human pituitary and its adenomas.

Estrogen affects the synthesis and release of several pituitary hormones. The estrogen receptor (ER), a member of the steroid hormone receptor family, is thought to mediate transcriptional effects in a cell-specific fashion. We investigated whether ER is expressed in specific hormone-producing cell types in the human pituitary and its adenomas. Pituitary adenomas (n = 34) were collected at the time of surgery, and normal glands were obtained from autopsy. Expression of ER messenger ribonucleic acid (mRNA) was determined by reverse transcription-polymerase chain reaction (RT-PCR) and in situ hybridization. ER was also localized with immunohistochemistry and protein extraction. By RT-PCR, ER mRNA was found in the nontumorous pituitary and in pituitary adenomas expressing only PRL, in those producing GH and PRL, and in adenomas expressing the gonadotropic hormones. No ER mRNA was detected in adenomas expressing only GH without PRL or gonadotropins, nor in tumors producing ACTH without PRL or gonadotropins. In situ hybridization was not as sensitive or specific as RT-PCR. Biochemical analysis performed on seven tumors that were positive for ER mRNA by RT-PCR detected ER protein in only one PRL adenoma and one oncocytoma and yielded negative or equivocal results in one PRL adenoma, three GH-PRL adenomas, and one null cell adenoma. ER protein was localized by immunohistochemistry in scattered cells of the nontumorous adenohypophysis and in a few PRL and gonadotroph adenomas. We conclude that ER expression, as determined by RT-PCR, correlates with the expression of PRL or gonadotropins; in contrast, ER mRNA was not detected in adenomas that express only GH or ACTH. These findings implicate ER as a cell-specific transcription factor that may regulate cytodifferentiation in the pituitary.

Steroid hormone receptors in astrocytic neoplasms.

The presence of specific steroid hormone-binding receptors has been correlated with the clinical response to hormonal therapy in a number of different neoplasias, including breast and prostate cancer. In this article, we investigated the expression of the androgen, estrogen, glucocorticoid, and progesterone receptor messenger ribonucleic acid (mRNA) and protein in a number of astrocytic neoplasms of various histological grades. Androgen and glucocorticoid receptor mRNA were detected in all astrocytic neoplasms examined, regardless of histological subtype. In contrast, progesterone receptor mRNA was observed more frequently in high-grade tumors than in low-grade tumors. Estrogen receptor mRNA was undetectable in all astrocytic tumors examined. These studies suggest a possible adjunct clinical use of hormonal therapy for the treatment of astrocytomas. Specific antagonists and agonists may allow the modulation of the growth of these tumors. Development of this body of knowledge may lead to the development of better treatment for these aggressive tumors.

Changes in estrogen receptor messenger ribonucleic acid in sheep fetal and maternal tissues during late gestation and labor

OBJECTIVE: Our purpose was to investigate whether there is an increase in messenger ribonucleic acid for estrogen receptor in critical maternal or fetal tissues in the last third of pregnancy and during labor in sheep. STUDY DESIGN: Estrogen receptor messenger ribonucleic acid was measured by Northern hybridization analysis in fetal-placental and maternal uterine tissues during the last third of pregnancy and during spontaneous or cortisol-induced labor in sheep. Statistical differences were assessed with two-way analysis of variance. RESULTS: No estrogen receptor messenger ribonucleic acid was observed in amnion or chorion in any animal studied. There were no gestational age related changes in estrogen receptor messenger ribonucleic acid in any tissues between 100 and 145 days' gestation. During spontaneous and cortisol-induced labor estrogen receptor messenger ribonucleic acid increased significantly ( p < 0.05) in myometrium, endometrium, and cervix. No increase was observed in the fetal placental cotyledon and mesometrium. Estrogen receptor messenger ribonucleic acid was markedly decreased ( p < 0.05) in myometrium and endometrium after fetal adrenatectomy. CONCLUSION: An increase in estrogen receptor messenger ribonucleic acid in association with labor may contribute part of the mechanism by which estrogens exert their influence on the process of parturition.

Estrogen receptors are present in human granulosa cells.

Recent studies failed to detect estrogen receptors in primate follicles. This study was initiated to determine whether estrogen receptor (ER) messenger ribonucleic acid (mRNA) is present in human granulosa cells and, further, if functional ER proteins are present. To evaluate the presence of ER, RNA from human granulosa cells obtained at the time of oocyte retrieval for assisted reproduction was extracted, and complementary DNA synthesis was performed by the reverse transcriptase-polymerase chain reaction. Oligonucleotide primers were used to amplify basepairs 570-852 in the B- and C- domains of the ER mRNA. Southern blotting was performed and confirmed that the amplified DNA fragment identified in granulosa cells represented ER. By reverse transcriptase-polymerase chain reaction, mRNA for the ER is clearly identified in primary human granulosa cells obtained at the time of oocyte retrieval. To expand these studies and determine whether functional ER were present in human granulosa cells in culture, a simian virus-40-transformed human granulosa cell line was studied. Cells were transfected with a plasmid containing as estrogen response element up-stream from the bacterial reporter gene chloramphenicol acetyltransferase (CAT). In transfected cells, CAT activity is inducible by estradiol if endogenous functional ER are present. In these studies, the transfection analysis confirmed that functional, transcriptionally competent ER are present in a human granulosa cell line, with a 4- to 5-fold enhancement of CAT activity demonstrated after the addition of estradiol compared to that in nonhormone-treated cells. In conclusion, ER mRNA is present in human granulosa cells. Functional ER are also demonstrated in a transformed human granulosa cell line. We hypothesize that low, but biologically significant, amounts of ER protein are present in human granulosa cells, which are not routinely detectable by standard assays.

Sex differences in estrogen and progesterone receptor messenger ribonucleic acid regulation in the brain of little striped whiptail lizards.

Sex differences in the regulation of steroid hormone receptors in brain areas controlling female- and male-typical sexual behavior may be important in determining sex differences in the display of these behaviors. This study examined sex differences in estrogenic effects on the relative abundance of messenger RNA for estrogen receptor (ER) and progesterone receptor (PR) in discrete brain areas of whiptail lizards, Cnemidophorus inornatus, by in situ hybridization with radiolabeled riboprobes. Gonadectomized females and males received an estradiol benzoate (EB) injection (0.5 microgram) which effectively induces receptive behavior in females; controls received vehicle alone. Sex and regional differences in estrogenic effects on ER- and PR-mRNA abundance were found. Females responded to EB treatment with increases in ER- and PR-mRNA relative abundance in the ventromedial nucleus of the hypothalamus (VMH). Males had similar relative mRNA abundances to females in gonadectomized controls, but did not exhibit increases with EB treatment. EB treatment increased ER-mRNA abundance in the dorsal hypothalamus of females, but not males. ER-mRNA decreases in the lateral septum and PR-mRNA increases in the posterior hypothalamus with hormone treatment were also found, but did not differ by sex. Neither sex nor treatment effects were definitively shown for ER- or PR-mRNA abundance in the anterior hypothalamus-preoptic area. The VMH controls female-typical receptive behavior in this species. Sex differences in the response to estrogen in this nucleus may therefore underlie sex differences in the display of receptive behavior.(ABSTRACT TRUNCATED AT 250 WORDS)

Estrogen receptor gene expression in craniopharyngiomas: an in situ hybridization study.

Craniopharyngiomas are histologically benign epithelial neoplasms of the sellar region that frequently exhibit invasive and aggressive local growth. In this study, we have investigated the presence and cellular distribution of estrogen receptor messenger ribonucleic acid by in situ hybridization in 23 surgically removed craniopharyngiomas. All craniopharyngiomas studied, including 19 adamantinomatous and 4 papillary variants, uniformly expressed the estrogen receptor gene. In all cases, an intense estrogen receptor messenger ribonucleic acid hybridization signal was demonstrated; one localized exclusively to the epithelial cells of the tumor. Connective tissue and vascular elements were devoid of hybridization signal. Coexpression of the estrogen receptor protein was also studied by immunohistochemistry. Despite the relative abundance of estrogen receptor message in all cases studied, the estrogen receptor protein was focally but conclusively detected in only two tumors. The basis of this discrepancy is unclear. Progesterone receptor protein was also studied in all cases; however, its definitive presence was noted in only one instance and, in that case, in only occasional nuclei. The expression of the estrogen receptor gene by the proliferative epithelial elements of craniopharyngiomas raises the questions of a possible hormonal component to the genesis and/or progression of the craniopharyngiomas and a potential responsiveness to therapeutic hormonal manipulation.

Altered expression of epidermal growth factor receptor and estrogen receptor in MCF-7 cells after single and repeated radiation exposures

Purpose : Studies on radiation-induced changes in gene expression are likely to be very important in developing a better understanding of cellular responses to ionizing radiation. While there is some information on the activation of cellular signal transduction pathways after radiation, few late reacting target genes have been identified. This study focuses on the characterization of expression modulation of two critical growth regulatory genes, estrogen receptor and epidermal growth factor-receptor in malignant mammary epithelial cells in response to single and repeated ionizing radiation exposures. Methods and Materials : MCF-7 cells were used for single radiation exposure (2–50 Gy) experiments and MCFIR-3 cells, generated by exposure to cumulative doses of 60 Gy in 2 Gy fractions, respectively, were used to study the effects of repeated exposures. Steady-state messenger ribonucleic acid levels for estrogen receptor, epidermal growth factor-receptor, and transforming growth factor-α were determined by ribonucleic acid protection experiments. Estrogen receptor and epidermal growth factor-receptor protein expression was quantitated by competitive binding studies with 3H-estradiol and 125I-EGF. Results : MCF-IR-3 cells showed a permanent three-fold down-regulation of the estrogen receptor messenger ribonucleic acid and protein, while epidermal growth factor-receptor was upregulated about nine-fold. Epidermal growth factor-receptor was substantially up-regulated in MCF-7 cells, at both the mRNA and protein levels, within 24 h of a single 2 Gy exposures, while there was a two-fold concomitant increase in transforming growth factor-α messenger ribonucleic acid expression. A decrease in estrogen receptor messenger ribonucleic acid and protein was suggested only after higher doses of single radiation exposures. Conclusion : Single and repeated radiation exposures modulate the expression of two critical growth promoting genes, estrogen receptor and epidermal growth factor-receptor, in MCF-7 cells. The inverse expression of estrogen receptor and epidermal growth factor-receptor established for estrogen receptor-positive malignant mammary epithelial cells is maintained in MCF-7 cells after single and repeated exposures suggesting that radiation acts through common regulatory circuits and may modulate the cellular phenotype.

In situ hybridization study of estrogen receptor messenger ribonucleic acid in human adenohypophysial cells and pituitary adenomas

In situ hybridization study of estrogen receptor messenger ribonucleic acid in human adenohypophysial cells and pituitary adenomas

Determination of estrogen receptor messenger ribonucleic acid (mRNA) and cytochrome P450 aromatase mRNA levels in adipocytes and adipose stromal cells by competitive polymerase chain reaction amplification.

Clinical evidence suggests that sex hormones affect adipose tissue metabolism and deposition. To investigate the biosynthesis and possible action of estrogen in adipose tissue, we report the use of competitive, specific polymerase chain reaction amplifications to determine levels of estrogen receptor (ER) messenger RNA (mRNA) and cytochrome P450 aromatase mRNA in adipocytes and adipose stromal cells. This extremely sensitive technique uses coamplification of a homologous animal species complementary RNA to control for differences in amplification efficiencies. The DNA amplification products are identified by Southern hybridization with species-specific radiolabeled oligonucleotide probes. Abdominal adipose tissue obtained from female patients during elective abdominoplasty was separated by collagenase digestion and centrifugation into floating adipocytes and pelleted adipose stromal cells. Our results demonstrate higher ER mRNA levels in adipocytes compared to adipose stromal cells, whereas cytochrome P450 aromatase mRNA levels are higher in adipose stromal cells compared to adipocytes. The finding of ER mRNA in adipose tissue suggests the presence of the ER in adipose tissue. In addition the inverse correlation of ER mRNA and cytochrome P450 aromatase mRNA levels in adipocytes and adipose stromal cells suggests a paracrine relationship whereby estrogen produced by adipose stromal cells affects adjacent adipocytes.

Determination of estrogen receptor messenger ribonucleic acid (mRNA) and cytochrome P450 aromatase mRNA levels in adipocytes and adipose stromal cells by competitive polymerase chain reaction amplification

Determination of estrogen receptor messenger ribonucleic acid (mRNA) and cytochrome P450 aromatase mRNA levels in adipocytes and adipose stromal cells by competitive polymerase chain reaction amplification

Enduring consequences of neonatal treatment with antisense oligodeoxynucleotides to estrogen receptor messenger ribonucleic acid on sexual differentiation of rat brain.

Sexual differentiation of the mammalian brain is regulated by steroids during a critical developmental period, particularly by estradiol, which is believed to be aromatized in brain from gonadally derived testosterone. To ascertain the importance of neuronal estrogen receptor expression during sexual differentiation, we infused a 15-mer oligodeoxynucleotide antisense to the region of the translation start codon of estrogen receptor messenger RNA (mRNA), into the hypothalamus of 3-day-old rat pups. Two separate control treatments consisted of either a scrambled nucleotide sequence oligodeoxynucleotide, which had little homology to known mRNAs, or vehicle. Female pups either received a lightly androgenizing dose of testosterone 6 h after oligo infusion or were not hormone treated. Infusion of antisense oligo to estrogen receptor mRNA protected against many of the androgenizing effects of testosterone. Androgenized females infused with antisense oligo were significantly more likely to exhibit female sexual behavior in adulthood after treatment with estrogen plus progesterone and remained sensitive to the induction of wheel-running behavior by estrogen treatment seen in normal females, whereas the control androgenized females did not. Normal females did not exhibit any effects of antisense oligo treatment on sexual or locomotor behavior, but antisense oligo-treated normal females showed a trend (P = 0.09) toward disrupted estrous cyclicity and behaved differently in tests of open field behavior compared to controls. After killing, brains were processed for histology. Morphometric analysis of the sexually dimorphic nucleus of the preoptic area demonstrated a significantly smaller volume in antisense oligo-infused androgenized females compared with vehicle and scrambled oligo-infused controls. The sexually dimorphic nucleus volume was smaller still in normal females infused with antisense oligo, consistent with estrogen receptor activation playing an active role in sexual differentiation of the female brain. These results demonstrate the effectiveness of antisense oligodeoxynucleotides in permanently altering a developmental process if administered during a critical period.

Enduring consequences of neonatal treatment with antisense oligodeoxynucleotides to estrogen receptor messenger ribonucleic acid on sexual differentiation of rat brain

Sexual differentiation of the mammalian brain is regulated by steroids during a critical developmental period, particularly by estradiol, which is believed to be aromatized in brain from gonadally derived testosterone. To ascertain the importance of neuronal estrogen receptor expression during sexual differentiation, we infused a 15-mer oligodeoxynucleotide antisense to the region of the translation start codon of estrogen receptor messenger RNA (mRNA), into the hypothalamus of 3-day-old rat pups. Two separate control treatments consisted of either a scrambled nucleotide sequence oligodeoxynucleotide, which had little homology to known mRNAs, or vehicle. Female pups either received a lightly androgenizing dose of testosterone 6 h after oligo infusion or were not hormone treated. Infusion of antisense oligo to estrogen receptor mRNA protected against many of the androgenizing effects of testosterone. Androgenized females infused with antisense oligo were significantly more likely to exhibit female sexual behavior in adulthood after treatment with estrogen plus progesterone and remained sensitive to the induction of wheel-running behavior by estrogen treatment seen in normal females, whereas the control androgenized females did not. Normal females did not exhibit any effects of antisense oligo treatment on sexual or locomotor behavior, but antisense oligo-treated normal females showed a trend (P = 0.09) toward disrupted estrous cyclicity and behaved differently in tests of open field behavior compared to controls. After killing, brains were processed for histology. Morphometric analysis of the sexually dimorphic nucleus of the preoptic area demonstrated a significantly smaller volume in antisense oligo-infused androgenized females compared with vehicle and scrambled oligo-infused controls. The sexually dimorphic nucleus volume was smaller still in normal females infused with antisense oligo, consistent with estrogen receptor activation playing an active role in sexual differentiation of the female brain. These results demonstrate the effectiveness of antisense oligodeoxynucleotides in permanently altering a developmental process if administered during a critical period.