Inhibition of dopamine release by prostaglandin EP3 receptor via pertussis toxin-sensitive and -insensitive pathways in PC12 cells

Prostaglandin EP3 receptor is involved in the inhibition of neurotransmitter release from presynaptic nerve terminals in various tissues. We have examined the regulation of neurotransmitter release by the EP3 receptor using a PC12 cell line that stably expresses the EP3B receptor isolated from bovine adrenal medulla. In the cells, M&B28767, an EP3 agonist, inhibited the 50 mM KCl- or 10 nM bradykinin-induced [3H]dopamine release in a concentration-dependent manner (10 pM to 0.1 microM). This inhibition was partially reversed by pretreatment with pertussis toxin, whereas under the same condition, the agonist-induced inhibition of forskolin-stimulated cyclic AMP accumulation was suppressed completely. In contrast, M&B28767 did not affect the high K(+)- or bradykinin-induced increase in intracellular Ca2+ concentration. Moreover, M&B28767 also inhibited the [3H]dopamine release induced by the Ca2+ ionophore ionomycin, and this inhibition was also partially reversed by pretreatment with pertussis toxin. These results indicate that the EP3 receptor is coupled to dual pathways, pertussis toxin-sensitive and -insensitive G-protein pathways, to regulate neurotransmitter release without changing Ca2+ influx in neuronal cells.

Purification and characterization of heterologously expressed mouse CYP2A5 and CYP2G1: role in metabolic activation of acetaminophen and 2,6-dichlorobenzonitrile in mouse olfactory mucosal microsomes

The metabolic activation of two known olfactory mucosal (OM) toxicants, acetaminophen (AP) and 2,6-dichlorobenzonitrile (DCBN), was examined with mouse liver and OM microsomes and purified, heterologously expressed mouse CYP2A5 and CYP2G1. In reconstituted systems, both isoforms were active in metabolizing DCBN and AP to metabolites that formed protein adducts. The formation of DCBN- or AP-protein adducts and other AP metabolites, including 3-hydroxy-AP and, in the presence of glutathione, AP-glutathione conjugate, was also detected in OM microsomal reactions and to a much greater extent than in liver microsomes. Evidence was obtained that CYP2A5 and CYP2G1 play major roles in mouse OM microsomal metabolic activation of DCBN and AP. Immunoblot analysis indicated that CYP2A5 and CYP2G1 are abundant P450 isoforms in OM microsomes. OM microsomal AP and DCBN metabolic activation was inhibited by 5- and 8-methoxsalen, which inhibit both CYP2A5 and CYP2G1, and by an inhibitory anti-CYP2A5 antibody that also inhibits CYP2G1. In addition, the roles of CYP1A2 and CYP2E1 in the OM bioactivation of AP and DCBN were ruled out by comparing activities of acetone-treated mice or Cyp1a2(-/-) mice with those of control mice. Thus, CYP2A5 and CYP2G1 may both contribute to the known OM-selective toxicity of AP and DCBN. Further analysis of the kinetics of AP and DCBN metabolism by the purified P450s suggested that CYP2A5 may play a greater role in OM microsomal metabolism of AP, whereas their relative roles in DCBN metabolism may be dose dependent, with CYP2G1 playing more important roles at low substrate concentrations.

Potentiation of retinoic acid-induced differentiation of HL-60 cells by prostaglandin EP2 receptor

Human promyeloid HL-60 cells are differentiated by all-trans retinoic acid (RA) to granulocytes, and prostaglandin (PG) E2 potentiates the RA-induced differentiation. Here we examined which subtype of PGE receptors was involved in this potentiating activity of PGE2. Northern blot analysis demonstrated that HL-60 cells expressed three subtypes of PGE receptor, EP2, EP3, and EP4. Among various EP agonists, and EP2-selective agonist, butaprost, preferentially potentiated the RA-induced differentiation of HL-60 cells. Butaprost not only decreased the half-maximal concentration of RA but also increased the maximal level of the differentiation. Butaprost concentration-dependently stimulated the cAMP formation, and 8-Br-cAMP strongly potentiated the RA-induced differentiation. These results demonstrate that the EP2 receptor enhances the RA-induced differentiation of HL-60 cells via stimulation of adenylate cyclase.

Role of CYP2A5 and 2G1 in acetaminophen metabolism and toxicity in the olfactory mucosa of the Cyp1a2(-/-) mouse

Acetaminophen (AP) is a widely-used analgesic agent that has been linked to human liver and kidney disease with prolonged or high-dose usage. In rodents, the target organs that are affected include liver, kidney, and the olfactory mucosa. AP toxicity requires cytochrome P450(CYP)-mediated metabolic activation, and the isozymes CYP1A2, 2E1, and 3A are known to activate AP in the human. In the present study, we determined that olfactory mucosal toxicity of AP was not different between the Cyp1a2(+/+) wild-type and the Cyp1a2(-/-) knockout mouse, whereas the hepatic toxicity of AP was significantly diminished in Cyp1a2(-/-) mice. Western blots of olfactory mucosa revealed that CYP2E1 and CYP3A levels are similar between untreated Cyp1a2(+/+) and Cyp1a2(-/-) mice. Diallyl sulfide (DAS), a known inhibitor of CYP2E1 and of CYP2A10/2A11 (the rabbit orthologue of mouse CYP2A5), completely eliminated olfactory toxicity of AP in both the Cyp1a2(-/-) and wild-type mouse olfactory mucosa. We found that heterologously expressed mouse CYP2A5 and CYP2G1 enzymes (known to be present in olfactory mucosa) form 3-hydroxyacetaminophen (3-OH-AP) and 3-(glutathion-S-yl)acetaminophen (GS-AP); CYP2A5 is considerably more active than 2G1. Addition of GSH caused increases in GS-AP proportional to decreases in 3-OH-AP, suggesting that these two metabolites arise from a common precursor or are formed by way of competing pathways. We also found that both CYP2A5 and CYP2G1 are inhibitable by DAS in vitro. These studies provide strong evidence that, in addition to CYP2E1, CYP2A5 and 2G1 are important in AP bioactivation in the mouse olfactory mucosa and that CYP1A2 appears to be of minor importance for AP olfactory toxicity.

Molecular cloning and characterization of a novel nuclear protein kinase in mice

We cloned cDNAs which encode a mouse liver nuclear protein with an apparent molecular mass of 51 kDa, using sequences derived from a purified protein as the basis for designing specific primers. The deduced amino acid sequences revealed that the 51-kDa protein contains characteristic subdomain structures of a protein kinase. The bacterially expressed recombinant 51-kDa protein catalyzed phosphorylation of general substrates such as casein and was autophosphorylated at serine residue(s). This 51-kDa protein kinase, designated 51PK, is 40% identical to the 34-kDa protein kinase encoded by the vaccinia virus B1 gene and 25% identical to the casein kinase I isoforms, including yeast HRR25. The 51PK mRNA was expressed as two splice variants and the 51PK protein was exclusively localized in nuclei. Northern hybridization showed that 51PK mRNA was expressed in various tissues, with highest levels in testis, spleen, lung, and liver. These results, therefore, indicate that 51PK is a nuclear serine/threonine kinase and a novel distinct member of the protein kinase superfamily.

Activation by diverse xenochemicals of the 51-base pair phenobarbital-responsive enhancer module in the CYP2B10 gene

By extending previous studies of the phenobarbital (PB)-responsive 132-base pair (bp) enhancer sequence in the CYP2B10 gene, we have delimited a 51-bp enhancer element that is fully inducible by PB in mouse primary hepatocytes. Sixteen structurally unrelated phenobarbital-type inducers activated the 51-bp enhancer element in transient transfection assays. The results thus indicate that most PB-type inducers, if not all inducers, increase the transcription of the CYP2B10 gene by activating this 51-bp element, now designated PB-responsive enhancer module or PBREM.

Characterization of the gene for the mouse prostaglandin E receptor subtype EP2: tissue-specific initiation of transcription in the macrophage and the uterus

Genomic DNA clones for the mouse prostaglandin (PG) E receptor subtype EP2 were isolated and characterized. The mouse EP2 gene is composed of 2 exons and 1 intron, and spans 16 kb. The intron which is approx. 12 kb in length is located at the end of the sixth transmembrane domain, as with other prostanoid receptor genes. Based on this structure, transcripts were analysed in endotoxin-treated macrophages and pseudopregnant uteri, in which abundant expression of EP2 mRNA was observed. Sequence analysis of cDNA clones from these origins and Northern hybridization of these RNAs revealed that the uterine EP2 mRNA (U-type) has a longer 5'-untranslated region than the macrophage EP2 transcript (M-type). The major transcription initiation sites for M-type and U-type EP2 are located 124 and 769 bp upstream of the translation start site, respectively. The M-type was expressed in various tissues, whereas the U-type was found only in the uterus. The 2 kb segment containing the immediate 5'-flanking and 5'-noncoding regions contain three consensus sequences for the NF-IL6 binding site, one consensus sequence for the NF-kappaB binding site, four AP-2 consensus sequences, one AP-4 consensus sequence, one potential cAMP response element, and one potential progesterone response element. These results suggest that EP2 gene expression in the macrophage and uterus is under the control of distinct mechanisms involving alternative promoters.

Cytoskeletal regulation of the signal transduction of prostaglandin EP4 receptor

Prostaglandin (PG) EP4 receptor is coupled to Gs, stimulating adenylate cyclase. We tested whether cytoskeleton modulates the signal transduction of the EP4 receptor. A microtubule depolymerizing agent, colcemid, enhanced the PGE2-induced cAMP formation in the cloned EP4 receptor-expressing Chinese hamster ovary cells, but enhanced neither NaF plus AlCl3 nor forskolin-induced cAMP formation. Other microtubule depolymerizing agents, including colchicine, also induced the enhancement. These effects stemmed from the action of the agents on microtubules, because beta-lumicolchicine, an inactive isomer of colchicine, had no effect. In contrast, the microfilament depolymerizing agents did not affect the PGE2-induced cAMP formation but potentiated the enhancing effect of colcemid. This enhancement by colcemid was not due to the suppression of the desensitization of the EP4 receptor. The enhancing effect of colcemid was also observed in another Gs-coupled PGE receptor subtype, EP2 receptor. These results demonstrate that the state of microtubule assembly modulates the signal transduction of the EP4 receptor in concert with microfilament.

Protein serine/threonine phosphatase inhibitors suppress phenobarbital-induced Cyp2b10 gene transcription in mouse primary hepatocytes

Using a primary hepatocyte culture in which the mouse Cyp2b10 gene transcription is activated by phenobarbital (PB)-type inducers, we examined the cellular signalling mechanisms associated with PB induction. Low nanomolar concentrations of protein serine/threonine phosphatase inhibitors okadaic acid (OA) and calyculin A blocked the induction of CYP2B10 mRNA. Nuclear run-on assays indicated that OA suppressed Cyp2b10 gene transcription. Pretreatment of the cells with an inhibitor of Ca2+/calmodulin-dependent protein kinases ¿1-[N, O-bis-(5-isoquinolinesulphonyl)-N-methyl-L-tyrosyl]-4- phenylpiperazine (KN-62)¿ or with a flavonoid, naringin, were completely or partly protective respectively against the OA-mediated suppression of CYP2B10 mRNA. Several other established modulators of protein kinase activities did not greatly affect the induction of CYP2B10 mRNA, nor could they prevent the suppressive effect of OA. Our results indicate that specific protein phosphorylation-dephosphorylation is required for the induction of Cyp2b10 gene expression, which is modulated through multiple endogenous and exogenous signals.

Mouse steroid sulfotransferases: substrate specificity and preliminary X-ray crystallographic analysis

Three mouse cytosolic sulfotransferases were expressed in Escherichia coli cells in order to study their substrate specificities toward natural as well as synthetic steroid hormones. The Km and Vmax values confirmed the high substrate specificity of estrogen and hydroxysteroid sulfotransferases toward estradiol and dehydroepiandrosterone, respectively. In sharp contrast, the synthetic estrogen diethylstilbestrol was metabolized efficiently by both enzymes to its disulfate ester. These sulfotransferases display highly stereospecific sulfotransferase activity for sulfating only the trans-isomer of diethylstilbestrol. Crystals suitable for high-resolution structure determination of estrogen sulfotransferase were grown with polyethylene glycol. The crystals belong to the orthorhombic space group P2(1)2(1)2, and diffracted to 2.5 A.

p160 RhoA-binding kinase ROKalpha induces neurite retraction

We previously reported that the activation of prostaglandin E receptor EP3 subtype caused neurite retraction via small GTPase Rho in the EP3B receptor-expressing PC12 cells (Katoh, H., Negishi, M., and Ichikawa, A. (1996) J. Biol. Chem. 271, 29780-29784). However, a potential downstream effector of Rho that induces neurite retraction was not identified. Here we examined the morphological effect of p160 RhoA-binding kinase ROKalpha, a target for RhoA recently identified, on the nerve growth factor-differentiated PC12 cells. Microinjection of the catalytic domain of ROKalpha rapidly induced neurite retraction similar to that induced by microinjection of a constitutively active Rho, RhoV14, whereas microinjection of the kinase-deficient catalytic domain of ROKalpha did not induce neurite retraction. This morphological change was observed even though C3 exoenzyme, which was known to inactivate Rho, had been preinjected. On the other hand, microinjection of the Rho-binding domain or the pleckstrin homology domain of ROKalpha inhibited the EP3 receptor-induced neurite retraction. These results demonstrate that ROKalpha induces neurite retraction acting downstream of Rho in neuronal cells.

Are estrogens carcinogenic during development of the testes?

Many chemicals in the environment mimic the female sex hormone, estrogen. Exposure to environmental estrogens during early fetal development was proposed by Sharpe & Skakkebaek as a potential risk factor for subsequent testicular disease, including neoplasia and poor semen quality. To understand the mechanisms of action of estrogenic chemicals during differentiation of the male genital tract, we have studied developmental exposure to the synthetic estrogen, diethylstilboestrol (DES). While DES is a much more potent estrogen than most environmental chemicals examined, several of these compounds share some of the same properties as DES, such as a relative lack of binding to serum estrogen carrying proteins. Prenatal exposure to DES is associated with poor semen quality, prostatic disease, cryptorchidism and testicular neoplasia in mice. A rare form of testicular cancer, rete testis carcinoma, was observed in five percent of male mice treated in utero with DES. We also demonstrated altered regulation of an estrogen responsive gene, lactotransferrin (LTF) in the seminal vesicles of treated mice, but not the controls. Likewise, LTF was irreversibly altered in the uteri of developmentally treated females; at the molecular level altered methylation of the gene appears to be involved, thus, providing a potential marker for hormonal effects during development. The induction of permanent or "imprinted" responses during the development of a relatively estrogen-free reproductive tract cell suggests that undifferentiated targets for estrogen action may be sites for subsequent growth and differentiation defects associated with neoplasia.

Mouse glycine N-methyltransferase is sexually dimorphic and regulated by growth hormone

The secretion pattern of putuitary growth hormone (GH) in rodents is sexually dimorphic and regulates the expression of some hepatic genes. We report cloning of mouse glycine N-methyltransferase (GNMT) cDNA. The mouse GNMT mRNA is expressed at much lower levels in male than in female livers. Hypophysectomy in male mice resulted in as a high level of the expression as in female mice. Treatment with GH of hypophysectomized male mice twice a day for 5 days decreased the expression. These results indicate that the sex difference of the mouse GNMT expression is regulated by GH secretion patterns.

Crystal structure of estrogen sulphotransferase

The structure of estrogen sulphotransferase has been solved in the presence of inactive cofactor PAP and substrate 17 beta-estradiol. This structure reveals structural similarities between cytosolic sulphotransferases and nucleotide kinases.

Cellular localization and regulation of expression of testicular estrogen sulfotransferase

Estrogen sulfotransferase (EST) is a cytosolic enzyme that catalyzes the specific sulfonation of estrogens at the 3-hydroxyl position using 3'-phosphoadenosine-5'-phosphosulfate as an activated sulfate donor. Sulfated estrogens no longer bind to the estrogen receptor and are, therefore, hormonally inactive. Although liver has been considered a primary site for steroid sulfotransferase activities, we previously have cloned the mouse EST complementary DNA and found the enzyme to be expressed abundantly in the testis of normal mice. In this study we show by reverse transcription-PCR that EST is also expressed in the testes of rat and man, suggesting that testicular expression of EST may be a common phenomenon among different species. Using a purified polyclonal antibody raised against the bacterially expressed mouse EST protein, we demonstrate by immunohistochemistry that EST is localized selectively to the androgen-producing Leydig cells within the mouse testis. Additionally, we show that Leydig cell expression of EST is under the control of the pituitary hormone LH and is regulated differentially during development. In contrast to the high level of expression in mature intact animals, EST is not present in Leydig cells of hypophysectomized mice or in Leydig cells of fetal and prepubertal (day 5 or 17) mouse testes. Administration of hCG to hypophysectomized mice restored the testicular expression of EST. Together, these results suggest that testicular expression of EST may play an important role in male reproduction, conceivably by modulating the activity of locally synthesized estrogen in the testis of a sexually mature animal.

[Varicella in adulthood: clinical features, severity scores, source of infection and complications]

Varicella has been thought to be one of the representative infectious disease in childhood, but recently we are under the impression that adults contracting varicella are increasing in number. On the other hand, they say that varicella generally causes a serious illness in adult patients. So we investigated signs and symptoms of varicella, source of infection, occupations of adult patients, except those who were immunologically compromised, by means of medical records, to know the characteristics of varicella in adulthood. According to the varicella severity score proposed by Nagai et al., varicella in the hospitalized adult patient was found to be much severer than that in children. The most remarkable symptoms, were high fever and sore throat, and these were the main reason of hospitalization in most of our patients. Although severity scores were very high in admitted adult patients with varicella, their clinical courses were not serious, and most of them recovered with only supportive therapy. These patients rarely suffered from complications, like pneumonia. If adult patients with varicella hospitalized in the early stage and received supportive care, they could recover without any complications. In most cases of adult varicella the source of infection was unknown. In the case of married persons, however, many of them were infected through their child. When adults contract varicella, not only the patients themselves suffer from high fever and sore throat, but also they act as the source of infection, if they are medical care workers. Furthermore, in public, the contraction of varicella results a socioeconomic loss from suspension of business caused by the illness. Prophylaxis with varicella vaccine, therefore, should be considered, when there are people who have never contracted varicella, whether or not they are medical staff.

Somatic complaints associated with depressive symptoms in HIV-positive patients

BACKGROUND

Although several studies have indicated the association of mood states including depression with somatic complaints in HIV patients, there has been no report on Japanese HIV patients. The purpose was to examine the relationship between somatic complaints and mood states in HIV patients without AIDS.

METHODS

Subjects were 50 HIV patients without AIDS. As controls, we used 47 healthy persons without HIV, matched for age and gender of the subjects. After the Structured Clinical Interview for the DSM-III-R, several inventories including the Profile of Mood States (POMS) were administered. The presence or absence of somatic complaints were examined.

RESULTS

No patients fulfilled the criteria for the DSM-III-R Mood Disorders Including Major Depression. However, scores on depression as measured by the POMS were significantly higher for the HIV group than for the healthy group. Although depressive symptoms in the HIV group may not be strong enough to warrant a psychiatric diagnosis of mood disorders, these HIV patients may be prone to a depressive state. The HIV patients indicated somatic complaints more frequently. Among these, the presence or absence of five complaints (i.e., abdominal distress, sleep disturbance, smothering sensations, chest pain or discomfort, and numbness or chills) was significantly discriminated based on scores on depression.

DISCUSSION

The results suggest that depressive symptoms accompany several somatic complaints in HIV patients without AIDS. Although a longitudinal follow-up study is required, the assessments of somatic symptoms may bring clinical benefits such as earlier diagnosis and/or intervention for a depressive state.

Steroid hormone-dependent overexpression of cytochromes P450 2A in liver tumors of TGF alpha transgenic male mice

To clarify the mechanism underlying the male preference of liver tumor in transforming growth factor (TGF) alpha transgenic mice, we analyzed the sexually dimorphic expression of two P450s, i.e., female-specific mouse 15 alpha hydroxylase P450 (2A4) and coumarin 7-hydroxylase P450 (2A5). The expression of 2A4 mRNA in the livers of both transgenic and nontransgenic males was low compared with that in females. P450 2A5 mRNA in the transgenic males was slightly elevated in the adjacent non-tumorous tissues and dramatically elevated in the tumor compared with that in nontransgenic male liver. The activity of P450 2A5 was higher in females than in males in control and transgenic mice but the difference was smaller in the transgenic mice. The activity of P450 2A5 was exceptionally high in liver tumors of transgenic males, as indicated by mRNA expression. These results suggest that female-specific P450 2A5 is induced in the livers of TGF alpha transgenic male mice, particularly in liver tumors of transgenic male mice overexpressing TGF alpha, and may be useful as a marker for mouse hepatocarcinogenesis.

Developmental exposure to diethylstilbestrol elicits demethylation of estrogen-responsive lactoferrin gene in mouse uterus

Alteration of DNA demethylation in five CpG sites (-547, -533, -475, -464, and -454) immediately upstream from the estrogen response element of lactoferrin promoter was determined in the uteri of immature (17-day-old) and mature (21- and 30-day-old) mice treated neonatally with DES. Only the CpG/-464 was found to be abnormally demethylated by diethylstilbestrol (DES) treatment in the mature uteri. This abnormal demethylation occurred in specific response to DES in neonatal mice, because DES injected into the 30-day-old mature mice did not demethylate CpG/-464. This site, however, remained methylated in the neonatally DES-treated/ovariectomized mice, indicating that this DES-elicited demethylation is under hormonal control. Thus, neonatal DES treatment appeared to imprint an abnormal, site-specific demethylation of CpG/-464, which requires ovarian hormones to occur in adult mice. Moreover, the demethylation was maintained in uterine tumors of the neonatally DES-treated mice. This mode of demethylation is reminiscent of uterine tumor formation, which also depends on both neonatal DES exposure and ovarian hormone stimulation in adulthood. Thus, neonatal DES treatment may induce tumor formation as well as demethylation through a common cellular process.

Functional role of carboxyl-terminal tail of prostaglandin EP3 receptor in Gi coupling

We recently demonstrated that the mouse EP3beta receptor and its carboxyl-terminal tail-truncated receptor showed agonist-dependent and full constitutive Gi activities, respectively (Hasegawa, H., Negishi, M. and Ichikawa, A. (1996) J. Biol. Chem. 271, 1857-1860). To assess the role of the carboxyl-terminal tail in the EP3beta receptor Gi coupling, we constructed a series of mutant receptors with progressively truncated carboxyl-termini. The truncated receptors displayed constitutive Gi activities, the degree of constitutive activity basically correlating with the inverse of the length of the carboxyl-terminal tail, but the sequence between Leu340 and Val347 was mainly contributed to the constitutive activity. Thus, the carboxyl-terminal tail plays an important role in the constraint of the EP3 receptor in its inactive conformation.

Characterization of the mouse prostaglandin F receptor gene: a transgenic mouse study of a regulatory region that controls its expression in the stomach and kidney but not in the ovary

BACKGROUND

The actions of prostaglandin F2alpha are mediated by a cell-surface receptor (FP), but little is known about the regulation of FP gene expression. To clarify the mechanisms underlying tissue specific transcription of the mouse FP gene, we isolated and characterized mouse genomic DNA clones encoding FP.

RESULTS

Structural analysis revealed that the mouse FP gene is composed of three exons and two introns, and spans more than 11 kilobases. By primer extension and PCR analyses, the major transcription start site was identified as a cytosine nucleotide, but additional sites of transcription initiation were found in the ovary. There was no apparent difference in the FP gene transcription initiation site between the ovary, kidney and stomach. Sequence analysis of the putative promoter region showed only two potential SP-1 binding sites, but no other typical well-known consensus sequences. We generated transgenic mice with the potential promoter region of the FP gene connected to the lacZ reporter gene. Northern blot analysis showed that the pattern of expression of the transgene corresponded to that of FP expression, except in the ovary. Upon analysis by in situ hybridization, the lacZ gene transcripts were found to be expressed in the fundic glands in the stomach, and the cortical tubules in the kidney, in which endogenous FP transcripts were also expressed. On the contrary, expression of lacZ transcripts was not detected in the corpora lutea, where the highest expression of FP mRNA was observed.

CONCLUSIONS

These studies suggest that a separate control mechanism exists for FP expression in the ovary, distinct from the expression in the stomach and kidney.

Facilitatory effect of ventral cut of dorsal raphe nucleus on lordosis in female rats

The role of the ventral projections of the dorsal raphe nucleus (DRN) in regulating lordosis was examined in female rats. The ventral neural fibers of the DRN were transected by the horizontal circle-cut (VC), anterior (AVC) or posterior half-circle cut (PVC) at the same time as ovariectomy. Three weeks after the surgery, all the rats were implanted with a Silastic tube containing estradiol (E2). The behavioral test was started one day after E2-implantation, and 5 tests in total were carried out every other day. The results showed that the VC females had a higher lordosis quotient (LQ) than control rats. Furthermore, as well as females with the VC, a high score LQ was observed in the AVC rats but not in the PVC females, compared to those in the control animals. These results suggest that the anteroventral neural fibers of the DRN are involved in the lordosis inhibiting mechanisms in female rats.