Haiping Lu

Serotonergic neurones in the dorsal raphe nucleus that project into the medial preoptic area contain oestrogen receptor beta.

Serotonin is involved in female sexual behaviour in which the medial preoptic area (MPA) has a pivotal role. The present study used immunohistochemistry, in situ hybridization and retrograde transport analysis to investigate whether serotonin neurones in the dorsal raphe nucleus (DRN) of females projecting into the MPA contained oestrogen receptor α or β. The projection of serotonin neurones from the DRN to the MPA was confirmed using the microinjection of Fluoro‐Gold (FG), a fluorescent retrograde tracer, into the MPA of ovariectomized (OVX‐group) and OVX‐rats treated with oestradiol benzoate (E2‐group). A number of serotonin neurones in the DRN were labelled with FG, indicating that these serotonin neurones in DRN project their terminals into the MPA. FG‐labelled serotonin neurones expressed ERβ mRNA in the DRN, and the number of the serotonin neurones containing ERβ mRNA between the OVX‐group and the E2‐treated group was not significantly different. Serotonin neurones in the DRN did not express ERα‐immunoreactivity. Since previous findings showed that the density of serotonin‐immunoreactive fibres and the concentration of serotonin within the MPA was significantly lower in the E2‐group than the OVX‐group, our present observations suggested that the regulatory effects of E2 on the serotonergic neurone system in the MPA may be via ERβ within the serotonin‐containing cells in the DRN of female rats.

Immunocytochemical analysis of sex differences in calcitonin gene-related peptide in the rat dorsal root ganglion, with special reference to estrogen and its receptor

Previous studies have shown that the calcitonin gene-related peptide (CGRP) immunoreactivity in the central nervous system (CNS) of adult rats is sexually dimorphic and regulated by sex steroid. In the present study, we used immunocytochemistry to investigate the sex difference in CGRP-immunoreactive (IR) neurons in rat dorsal root ganglia (DRG). The numbers of CGRP-IR neurons at the cervical, lumbar and sacral levels in the female rats were significantly lower than those of the male rats. We also found that the number of CGRP-IR neurons at the lumbar level was increased in ovariectomized (OVX) rats, but was decreased in estradiol (E2)-treated rats (OVX+E2). A large number of estrogen receptor (ER)-IR neurons at the lumbar level were found in the female rats, and its number was greater than that in the male rats. We also investigated the change in the number of ER-IR neurons of OVX rats after estrogen treatment. The number of ER-IR neurons in the OVX+E2 rats was consistent with that of the intact female rats, but was significantly increased in the OVX rats. As shown by a double-labeling immunocytochemical method, over 80% of the CGRP-IR neurons at the lumbar level showed ER immunoreactivity in the female, OVX and OVX+E2 rats, compared to only about 46% in the male rats. These results indicate that there is a gender difference in CGRP expression in the rat DRG, and that this CGRP expression might be downregulated by estrogen (at least in part) through its receptor.

Steroid hormones and their receptors in the brain.

Steroid hormones regulate several important functions of the brain by altering the expression of particular genes through their receptors. First in this paper the localization of glucocorticoid receptor immunoreactivity and mRNA in the brain was examined. Second biphasic effects of glucocorticoid on the hippocampus was described and particular emphasis was given on the apoptosis. Third the significance of estrogen receptor in the sexually dimorphic areas was discussed. These results suggest that steroids modulate the gene expression along with the alteration of cell structures in a different manner in a tissue-specific pattern.

Cloning and characterization of LUN, a novel ring finger protein that is highly expressed in lung and specifically binds to a palindromic sequence.

We isolated cDNAs encoding a novel RING finger protein (LUN), the mRNAs of which were expressed at high levels in the lung. In situ hybridization revealed that LUN mRNAs were expressed in the alveolar epithelium of the lung. TheLUN gene locus was assigned to chromosome 9p21, which contains candidate tumor suppressor genes associated with loss of heterozygosity in more than 86% of small cell lung cancers. We clarified that LUN is localized to the nucleus and reveals Zn2+-dependent DNA binding activity. The region from amino acids 51 to 374 of LUN is responsible for DNA binding. Furthermore, we identified a novel palindromic binding consensus (5′-TCCCAGCACTTTGGGA-3′) for the LUN binding. Interestingly, this LUN binding palindromic sequence is found in the upstream transcriptional regulatory region of the E-cadherin gene and two intervening regions of the talin gene. Our results suggested that LUN might be an important trans-acting transcriptional regulator for lung cancer-associated genes including E-cadherin and talin genes.

Adrenalectomy-induced granule cell death is predicated on the disappearance of glucocorticoid receptor immunoreactivity in the rat hippocampal granule cell layer

In this study, we observed the changes of glucocorticoid receptor (GR)-immunoreactivity (ir) and cell death in the rat hippocampal granule cell layer at various periods after adrenalectomy (ADX). Our results revealed that all of the rats shortly after ADX showed a rapid loss of GR-ir and subsequent appearance of degenerating cells in the granule cell layer. One month after ADX, however, about 80% of the rats displayed a restoration of GR-ir and the absence of degenerating cells in the granule cell layer, and this phenomenon was successively noted for 6 months. Hippocampal structural destruction 3 and 6 months after ADX was found in about 20% of the rats with loss of GR-ir in the granule cell layer; the ADX rats with even weak GR-ir in this area had a normal hippocampus. The treatment of rats with synthetic GR agonist, dexamethasone, immediately after ADX prevented the loss of GR-ir and significantly reduced the number of degenerating cells in the granule cell layer. Our results clarified that granule cell death after ADX was necessarily accompanied by the disappearance of GR-ir in the granule cell layer, suggesting that ADX-induced granule cell death is predicated on the loss of GR-ir and that the presence of GR-ir in this area may be important for granule cell survival.

Estrogen reduces the neurite growth of serotonergic cells expressing estrogen receptors

Serotonergic innervation of the central nervous system has a sexual dimorphism. The serotonin level in the hypothalamus was modulated by estrogen, and the formation of sexual dimorphism of serotonergic fiber innervation in the hypothalamus has been shown by the effect of sexual hormone during the critical perinatal period. In this study, we examined the direct effect of estrogen on the neurite growth of serotonergic neurons in primary culture from embryonic day 14 (E14) of rat mesencephalon. The total neurite length of serotonin-immunoreactive (IR) cells was significantly decreased by estradiol benzoate (E2, 10(-8)M) treatment for 7 days, compared with the case of no treatment. Moreover, the presence of estrogen receptor (ER) alpha and ERbeta mRNA in the E14 mesencephalon with reverse transcription-polymerase chain reaction (RT-PCR), and the ERalpha or ERbeta protein in the cultured serotonin-IR cells with double fluorescence immunohistochemistry were also demonstrated. Our results suggest that the inhibitory effects of E2 on the neurite growth of serotonergic cells expressing ERalpha or ERbeta might be involved in the formation of the sexual dimorphic distribution of serotonergic innervation.

Effects of sex steroid hormone on serotonin in female rat brain: Immunohistochemistry, HPLC and in vivo microdialysis analysis

It has been shown that serotonin plays a key role on the sexual behavior of female rats. In this study, the effects of sex steroid hormones on serotonin in various region of female rat brain were investigated by using immunohistochemistry with image-analysis, HPLC and in vivo microdialysis. There was a significant decrease in the density of serotonin-immunoreactive fibers and concentration of serotonin of MPN and VMH in estrogenand estrogen/progesterone-treated rats, while no changes were observed in the lateral septum. Furthermore, the decrease in release of serotonin in MPN of estrogen-treated rat was noted by in vivo microdialysis. The present investigation revealed that estrogen and progesterone have a specific effect on the serotonin system in a region-specific manner.

2325 Effects of sex steroid hormone on serotonin-immunoreactivity in the female rat brain

CHANG-JIANG ZOU, TATSUSHI ONAKA, KINJI YAGI Conditioned fear stimuli suppress vasopressin (VP) and facilitate oxytocin (OT) secretion by the pituitary. In the previous experiment, depletion of central noradrenaline blocked the neuroendocrine responses to fear stimuli. The present study aimed to identify the adrenoceptor subtypes which are involved in these responses. Male Wistar rats were trained with environmental stimuli paired with footshocks and tested with the environmental stimuli on the following day. Immediately after the testing, blood samples were collected. Adrenoceptor antagonists were injected i.c.v. 30min before the testing. In the rats that received benoxathian, an oi-receptor antagonist, the VP and OT responses to conditioned fear stimuli disappeared. Metoprolol, a ,3i-receptor antagonist, selectively blocked the VP response but not the OT response to conditioned fear stimuli. ICI 118551, a &receptor antagonist, did not significantly change the VP and OT responses to conditioned fear stimuli. We conclude that oi-receptors are involved in the VP and OT responses and that Pi-receptors are selectively associated with the VP response to conditioned fear stimuli in