ISSN:0953-8194    

DOI:10.1111/j.1365-2826.1994.tb00623.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

Nitric oxide and estrogen have been shown to play a critical role in the control of female reproductive function. In order to determine an anatomical relationship between nitric oxide generating neurons and estrogen target neurons, NADPH‐diaphorase histochemistry was combined with estrogen receptor immunohistochemistry in the female medial preoptic area. While only a few weakly stained neurons for NADPH‐diaphorase were found in ovariectomized control rats, a drastic increase in NADPH‐diaphorase activity was observed in the medial preoptic nucleus of estradiol‐treated ovariectomized animals. The total number of NADPH‐diaphorase neurons in the estradiol‐treated group increased three‐fold relative to controls, and more than 80% of those neurons contained estrogen receptor‐immunoreactivity in their nuclei. Since neuronal NADPH‐diaphorase is nitric oxide synthase, the present result suggests that nitric oxide synthase activity can be positively regulated by estradiol in neurons containing estrogen receptor in the female medial

ISSN:0953-8194    

DOI:10.1111/j.1365-2826.1994.tb00624.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

AbstractWe tested the hypotheses that in the male rat, expression of proopiomelanocortin (POMC) mRNA in cells of the arcuate nucleus displays a diurnal fluctuation and that expression of this rhythm is dependent upon the secretory products of the testis. To accomplish this, we sacrificed groups of testes‐intact and castrated adult male rats throughout the day and compared levels of POMC mRNA in individual cells of the arcuate nucleus across time and between groups. Adult male rats were housed on a 12–12 L D cycle with lights on a 0600 h and were divided into groups that were either castrated or left intact. Four days later, pairs from these groups were sacrificed at 0600 h, 1200 h, 1800 h, 2400 h, and again at 0600 h (n = 4 per group at each time point). We usedin situhybridization and a computerized image analysis system to measure cellular levels of POMC mRNA, as reflected by the number of autoradiographic grains over individual cells in the rostral quarter of the arcuate nucleus (counting ∼ 30 cells per animal). Using cosinor analysis, we observed that in intact male rats, POMC mRNA levels varied significantly over the 24 h day with a nadir value at 1800 h. In contrast, there was no significant diurnal variation in POMC mRNA levels in castrated animals. POMC mRNA levels were significantly greater in the intact compared with castrated animals at every time point (P<0.01), except at 1800 h, when the groups did not differ significantly from one another. We conclude that adult male rats display at diurnal rhythm in cellular POMC mRNA levels in the arcuate nucleus, and we infer that testosterone or some other secretory product of the testis is a prerequisite for expression of this r

ISSN:0953-8194    

DOI:10.1111/j.1365-2826.1994.tb00625.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

AbstractEffects of gonadal steroids on numbers of neurons containing estrogen receptor (ER) and/or substance P (SP) were examined in the anteroventral periventricular nucleus (AVPV) of female and male rats by double‐labeling immunohistochemistry employing antibodies specific for ER and SP. Animals were gonadectomized and received subcutaneously either oil alone (Control group), sequential injections of estradiol benzoate and oil (EB + Oil group), or those of EB and progesterone (EB + P group). In the female control rat, a large population of ER‐immunoreactive (IR) cells were found clustered throughout the AVPV. They were counted more than 2,000 in total of 4 sections in this nucleus. On the contrary, SP‐IR neurons were scarcely observed in the same area of this group. Administration of estrogen to female animals decreased the total number of ER‐IR cells to 67% of the control group. In contrast to the supressive effect of estrogen to its own receptor, it induced SP‐IR neurons in the AVPV of the female. Approximately 50–80 SP‐IR neurons were counted in the 4 sections, and 59% of these neurons expressed ER‐IR material in their nuclei. In the female EB + P group, the number of ER‐IR neurons also decreased to 79% of the control group. Although the number of SP‐IR neurons in this group decreased to 32% of that in the EB + Oil group, a ratio of coexistence of ER‐IR material in these neurons increased to 75%. The male control group contained a smaller population of ER‐IR cells relative to the female control (1497 vs 2143). SP‐IR neurons were rarely observed as were in the female control. Administration of estrogen to the male also decreased the number of ER‐IR cells in a manner similar to that in the female. However, unlike the female, the steroid failed to induce the SP‐IR neurons in the male.These results demonstrate sexual dimorphism in the AVPV not only in the number of ER‐IR neurons but also in the responsiveness of SP neurons to estrogen. They further provide anatomical evidence that a subset of SP neurons are regulated by estradiol in estrogen sensitive neurons in the female rat. The data also suggest that this peptide is involved in mechanisms of luteinizing hormone surge by mediating actions

ISSN:0953-8194    

DOI:10.1111/j.1365-2826.1994.tb00626.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

AbstractJuvenile guinea pigs (18–20 days old) rarely display lordosis in response to estradiol and progesterone treatments that elicit sexual behavior in adult females. Nor do immature animals release a preovulatory‐like surge of luteinizing hormone in response to estradiol.In vitroradioligand binding assays have revealed similar concentrations of estrogen receptors in thehypothalamus and preoptic area of prepubertal and adult guinea pigs. The aim of the present study was to compare estrogen receptor‐immunoreactivity in a variety of forebrain regions of immature and adult guinea pigs, to determine whether age differences in estrogen receptor levels inmore discrete portions of the hypothalamus and preoptic area exist. Forebrain tissue from juvenile (17 days) and adult females (>6 weeks), ovariectomized 6 days previously, was processed forestrogen receptor‐immunoreactivity, using Abbott Laboratories' H222 anti‐human estrogen receptor antibody. Juveniles had estrogen receptor‐immunoreactive cells in all of the same regions as adults: medial preoptic area, medial preoptic nucleus, bed nucleus of the stria terminalis, periventricular, paraventricular, dorsomedial and arcuate nuclei, ventrolateral and anterior hypothalamic regions, and amygdala. Among the areas in which estrogen receptor‐immunoreactivity was quantified (medial preoptic area, medial preoptic nucleus, anterior periventricular nucleus, arcuate nucleus and ventrolateral hypothalamus), the only region in which an age difference in estrogen receptor‐immunostaining was observed was the rostral portion of the ventrolateral hypothalamus. Juvenile females had, on average, 30% fewer estrogen receptor‐immunoreactive cells in asample of this region than adults (440 ± 25 vs 626 ± 25, P = 0.001). These data are consistent with the hypothesis that insufficient estrogen receptors in the rostral ventrolateral hypothalamus may underlie, in part, the markedly deficient responses of juvenile female guine

ISSN:0953-8194    

DOI:10.1111/j.1365-2826.1994.tb00627.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

ISSN:0953-8194    

DOI:10.1111/j.1365-2826.1994.tb00628.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

AbstractGlucocorticoids (GC) are potent repressers of both basal and corticotropin releasing factor (CRF) stimulated transcription of the proopiomelanocortin (POMC) gene in corticotrope cells of the anterior pituitary. Despite the finding of a novel, high affinity glucocorticoid receptor (GR) binding site within the proximal region of the POMC promoter, the mechanism by which GC inhibit POMC transcription is still uncertain. Recent studies have described mechanisms whereby GC inhibit transcription of other genes via a direct interaction with components of the transcription factor AP‐1. Since it has been shown that CRF stimulates c‐fos in AtT‐20 corticotrope cells, and that c‐fos over‐expression elevates POMC transcription, the current study has investigated whether GC can repress c‐fos and c‐jun gene expression and AP‐1 DMA binding activity in AtT‐20 corticotrope cells. Acute treatment with doses of dexamethasone (DEX) that markedly inhibited nuclear POMC hnRNA had no effect on basal c‐fos mRNA expression, but resulted in a transient down regulation of c‐jun. In addition, acute DEX pretreatment significantly lowered CRF stimulation of POMC gene expression and attenuated the CRF stimulation of c‐fos mRNA by 25%. Although DEX treatment of AtT‐20 cells did not affect AP‐1 DNA binding capacity of nuclear extracts, DEX pretreatment blunted the stimulation of AP‐1 binding in response to CRF. In further studies, nuclear extracts from CRF‐treated cells were coincubated with nuclear extracts from control or DEX treated cells. High levels of DEX treated extracts led to a relative repression of CRF‐induced AP‐1 binding, suggesting that ligand‐activated GR may lower available AP‐1 levels by direct protein: protein interaction. Finally, the composition of AP‐1 in AtT‐20 nuclear extracts was found to be heterogeneous, with the variation dependent upon hormonal treatment. These data suggest that in the corticotrope cell relatively high levels of activated GR may influence CRF‐induced AP‐1 DNA binding via transient genomic actions on basal c‐jun and stimulated c‐

ISSN:0953-8194    

DOI:10.1111/j.1365-2826.1994.tb00629.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

AbstractLow amplitude pulses of estradiol‐17β (E2‐17β) are more effective than large single bolus injections or constant exposure to E2‐17β in inducing progesterone‐facilitated sex behavior in female rats and guinea pigs. The present study examined whether the increased responsiveness to E2‐17β is due to an increase in the number of estrogen receptors in the estrogen receptor rich areas of the hypothalamus and amygdala.Initial studies examined the rapid effects (20 min) of a high dose of E2‐17β (50 μg) on estrogen receptor immunostaining using either the H222 antibody or the ER 21 antiserum. ER 21 immunostaining was not affected by the E2‐17β treatment suggesting that it binds to both occupied and unoccupied estrogen receptors. Therefore the ER 21 antiserum was used to characterize the regulation of estrogen receptor immunoreactivity (ER‐IR) by E2‐17β.ER‐IR was examined for 48 h and serum E2‐17β for 24 h following a 2 μg s.c. injection of E2‐17β (a dose similar to that used in multiple pulse paradigms). Serum E2‐17β peaked 15 to 30 min following the injection and returned to baseline values by 1 h. In all but one area maximal suppression of ER‐IR occurred at 12 h.In summary, 1) decreases in estrogen receptor immunoreactivity following E2‐17β are consistent with studies in which estrogen receptors were assayed by binding assays and estrogen receptor mRNA was determined by in situ hybridization; 2) the ER 21 antiserum is able to detect both occupied and unoccupied estrogen receptors and 3) H222 immunoreactivity is influenced by the presence of E2‐17β, so that the level of H222‐IR is a reflection of ligand/receptor binding dynamics.The data suggest that up‐regulation of estrogen receptors does not account for the increase in behavioral sensitivity whic

ISSN:0953-8194    

DOI:10.1111/j.1365-2826.1994.tb00630.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

AbstractUsing mono ‐ and bilateral tarsal arthritic models in the rat, we have previously shown increases in the expression of mRNAs encoding substance P and calcitonin gene‐related peptide (CGRP) in primary sensory neurons innervating inflamed joints. Dorsal root ganglion (DRG) neuropeptide content in rats is altered by glucocorticoids, and since glucocorticoids regulate the expression of preprotachykinin (PPT) gene, the substance P precursor in other tissues, these effects may be mediated at the level of transcription. Indeed adrenalectomy potentiates disease in polyarthritis although the relationship to joint disease itself is unclear. Secretion of corticosterone in both mono ‐and bilaterally inflamed rats showed a loss of the normal diurnal nadir with no elevation of evening values. However, there were no changes in glucocorticoid target organs (adrenal gland, thymus and spleen) suggesting the stress was intermittent. Adrenalectomy in mono ‐ and bilaterally inflamed rats did not significantly alter either the severity of inflammation or its spread. Bilaterally inflamed animals did, however, show reduced weight gain. Adrenalectomy had no effect on the induction of PPT and CGRP mRNA expression in innervating DRG neurons in monoarthritis (14 days after adjuvant injection), the unilateral increase in both PPT and CGRP mRNA expression in ADX animals being similar to SHAM arthritic rats. (PPT: ADX 140 ± 13 left; 99 ± 6 right % control; SHAM 160 ± 22 left, 100 ± 5 right % control. CGRP: ADX 177 ± 6 left, 97 ± 3 right % control; SHAM 147 ± 21 left, 100 ± 5 right % control). In bilaterally arthritic rats adrenalectomy potentiated the increase in CGRP mRNA expression (SHAM 168 ± 6% left, 271 ± 23% right; ADX 217 ± 38% left, 193 ± 4% right; control 100 ± 5%) but significantly attenuated the contralateral (right) increase in PPT mRNA expression seen in sham‐operated rats (SHAM 136 ± 21% left; 140 ± 11% right; ADX 145 ± 28% left, 86 ± 15% right; control 100 ± 5%). Inflammation‐associated changes in somatostatin mRNA expression were similar in sham‐operated and adrenalectomized rats. We conclude, therefore, that whilst adrenalectomy exerts subtle effects on the expression of PPT and CGRP mRNAs in DRG neurons in bilateral arthritis, the presence or absence of high circulating endogenous corticosteroids in these animals, with limited arthritis, do not

ISSN:0953-8194    

DOI:10.1111/j.1365-2826.1994.tb00631.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

AbstractThe existence of neutral endopeptidase (Enkephalinase, NEP, E.G.3.4.24.11) in membranes of nerve endings in the rat median eminence suggests that some neuropeptides have paracrine and/or autocrine actions in this region.In vitro, neutral endopeptidase is capable of hydrolysing a variety of regulatory peptides butin vivo, many works indicate that in the central nervous system this enzyme is highly implicated in the biological inactivation of enkephalins and tachykinins. In addition there is evidence that NEP is also involved in the inactivation of neurotensinin vivo.The modulation of the release of gonadotrophin releasing hormone (GnRH) is one of the documented actions of enkephalins within the median eminence. However, it is at present unclear whether enkephalins act on dopamine endings, on GnRH endings or on both.As the technical parameters and particularly the tissue fixation used to detect neutral endopeptidase are compatible with immunocytochemical detection of GnRH and tyrosine‐hydroxylase (the rate limiting enzyme in the synthesis of catecholamines), two double immunolabelings were realised at the ultrastructural level to determine if GnRH and dopamine nerve endings have the enzyme inserted within their plasma membrane.Our study shows the presence of neutral endopeptidase on tyrosine‐hydroxylase‐immunoreactive nerve endings while presence of the enzyme on GnRH‐immunoreactive nerve endings is not demonstrated. Consequently, our results provide morphological arguments for possibilities of paracrine and/or autocrine actions by neuropeptides inactivated by neutral endopeptidase on tuberoinfundibular dopa‐minergic nerve endings. Conversely, action of the same peptides on GnRH boutons seems more

ISSN:0953-8194    

DOI:10.1111/j.1365-2826.1994.tb00632.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY