Biomedical subjects

T Moriya

Publications and source records attributed to T Moriya.

At least 73 records · Page 4Linked to original sources

PubMed2001

Hypoxia reduces hormone responsiveness of human breast cancer cells.

Resistance to hormonal therapy frequently occurs following successful treatment in breast cancer. The mechanism responsible for this acquired resistance is still unknown. It has been suggested that a hypoxic tumor microenvironment promotes malignant progression of cancer, i.e., hypoxia may promote estrogen-independent growth (a more malignant phenotype) of breast cancer. To clarify this hypothesis, the effects of hypoxia on the growth responses to hormonal agents and the expression levels of estrogen receptor (ER)-alpha and progesterone receptor (PgR) were investigated in two human breast cancer cell lines, ML-20 and KPL-1. The expression level of ER-alpha was significantly decreased by hypoxia (1% O(2)) in a time-dependent manner in both cell lines. Hypoxia also significantly reduced the growth-promoting effect of estradiol (E2) and the growth-inhibitory effects of an antiestrogen, ICI 182 780, and a progestin, medroxyprogesterone acetate, in both cell lines. In addition, hypoxia markedly suppressed the induction of PgR mRNA and protein by E2 in both cell lines. To clarify further the effect of hypoxia on ER-alpha expression, the expression levels of hypoxia-inducible factor-1 alpha (HIF-1 alpha), a marker of hypoxia and ER-alpha were immunohistochemically examined in 36 breast cancer specimens. ER-alpha expression (both its proportion and intensity) was significantly lower in nuclear HIF-1 alpha-positive tumors than in negative tumors. These findings indicate that hypoxia down-regulates ER-alpha expression as well as ER-alpha function in breast cancer cells. These processes may lead to an acquired resistance to hormonal therapy in breast cancer.

Breast Neoplasms↗

PubMed2001

Progesterone receptor A and B isoforms in the human breast and its disorders.

Two different isoforms of progesterone receptor (PR), PRA and PRB, are expressed in target tissues at comparable levels. In this study, we first examined PRA and PRB immunoreactivity in human breast cancer and various intraductal proliferative epithelial lesions, and correlated these findings with clinicopathologic parameters. We then examined mRNA expression of PRA and PRB in six cases of invasive ductal carcinoma using RT-PCR. Immunoreactivity for both PRA and PRB was positive in the great majority of proliferative disease without atypia (PDWA) (85% for PRA and 96% for PRB) and atypical ductal hyperplasia (ADH) (100% for PRA and 100% for PRB), but the ratio of immunopositive cases and immunohistochemical (IHC) scores was significantly smaller in ductal carcinoma in situ (DCIS) (65% for PRA and 75% for PRB) and invasive ductal carcinoma (IDC) (66% for PRA and 55% for PRB) than in PDWA and ADH. There was a significant positive correlation between IHC scores for PRA and estrogen receptor alpha (ERalpha) in IDC, DCIS and ADH but not between PRB and ERalpha. In IDC, both PRA and PRB IHC scores were significantly associated with histological grade, but there was no association between PRA or PRB status and lymph node involvement, tumor size, or prognosis of the patients. The expression of mRNAs for both PRA and PRB was detected in all six cases of IDC examined. These results suggest that both PRA and PRB are strongly associated with ERalpha in human breast and this relation may be disturbed in breast cancer.

Breast↗

PubMed2001

Expression of 5alpha-reductases in human epithelial ovarian cancer: its correlation with androgen receptor status.

Androgen metabolism and possible actions are considered to play some roles in human epithelial ovarian neoplasms, but the details have not been well studied. We have examined the expression of 5alpha-reductase type 1 and type 2, which catalyze the conversion of testosterone to more active androgen, 5alpha-dehydrotestosterone, and androgen receptor (AR), using immunohistochemistry (104 cases) and reverse transcription-polymerase chain reaction (RT-PCR) (16 cases) as a first step toward understanding the metabolism and possible actions of androgens in human common epithelial ovarian carcinoma. 5alpha-Reductase type 1 was immunopositive in 75 / 104 cases (72.0%), and 5alpha-reductase type 2 in 52 / 104 cases (50.0%) (P < 0.001). There was no significant correlation between patterns of immunolocalization and clinicopathological parameters examined. Median labeling index (LI) for AR was 17.8% (range 0 - 84.4%) which was significantly higher in serous carcinoma than other histological types (P < 0.001). There was a significant positive correlation between 5alpha-reductase type 1 immunoreactivity and AR LI (P = 0.0027), but no significant correlation was detected in 5alpha-reductase type 2. Results of RT-PCR analysis were also consistent with those of immunohistochemistry. The relatively wide distribution of 5alpha-reductase type 1, and its correlation to AR status in human epithelial ovarian malignancies suggest that this isozyme plays important roles in androgen metabolism and actions in these tumors.

3-Oxo-5-alpha-Steroid 4-Dehydrogenase↗

PubMed2001

Sensitized increase of period gene expression in the mouse caudate/putamen caused by repeated injection of methamphetamine.

Methamphetamine (MAP) causes the sensitization phenomena not only in MAP-induced locomotor activity, dopamine release, and Fos expression, but also in MAP-induced circadian rhythm. Cocaine-induced sensitization is reportedly impaired in Drosophila melanogaster mutant for the Period (Per) gene. Thus, sensitization may be related to induction of the Per gene. A rapid induction of mPer1 and/or mPer2 in the suprachiasmatic nucleus after light exposure is believed to be necessary for light-induced behavioral phase shifting. Although the caudate/putamen (CPu) expresses mPer1 and/or mPer2 mRNA, the function of these genes in this nucleus has not yet been elucidated. Therefore, we examined whether MAP affects the expression of mPer1 and/or mPer2 mRNA in the mouse CPu. Injection of MAP augmented the expression of mPer1 but not mPer2 or mPer3 in the CPu, and this MAP-induced increase in mPer1 expression lasted for 2 h. Also, the MAP-induced increase of mPer1 mRNA was strongly antagonized by pretreatment with a dopamine D1 receptor and N-methyl-D-aspartate (NMDA) receptor antagonist, but not by a D2 receptor antagonist. Interestingly, application of either the D1 or the D2 agonist alone did not cause mPer1 expression. The present results demonstrate that activation of both NMDA and D1 receptors is necessary to produce MAP-induced mPer1 expression in the CPu. Repeated injection of MAP caused a sensitization in not only the locomotor activity but also mPer1 expression in the CPu without affecting the level of mPer2, mPer3, or mTim mRNA. Thus, these results suggest that MAP-induced mPer1 gene expression may be related to the mechanism for MAP-induced sensitization in the mouse.

Animals↗

PubMed2001

Physical and inflammatory stressors elevate circadian clock gene mPer1 mRNA levels in the paraventricular nucleus of the mouse.

Stress induces secretion of corticosterone through activation of the hypothalamic-pituitary-adrenal axis. This corticosterone secretion is thought to be controlled by a circadian clock in the suprachiasmatic nucleus (SCN). The hypothalamic paraventricular nucleus (PVN) receives convergent information from both stress and the circadian clock. Recent reports demonstrate that mammalian orthologs (Per1, Per2, and Per3) of the Drosophila clock gene Period are expressed in the SCN, PVN, and peripheral tissues. In this experiment, we examined the effect of physical and inflammatory stressors on mPer gene expression in the SCN, PVN, and liver. Forced swimming, immobilization, and lipopolysaccharide injection elevated mPer1 gene expression in the PVN but not in the SCN or liver. A stress-induced increase in mPer1 expression was observed in the corticotropin-releasing factor-positive cells of the PVN; however, the stressors used in this study did not affect mPer2 expression in the PVN, SCN, or liver. The present study suggests that a stress-induced disturbance of circadian corticosterone secretion may be associated with the stress-induced expression of mPer1 mRNA in the PVN.

Animals↗

PubMed2001

5alpha-reductases in human breast carcinoma: possible modulator of in situ androgenic actions.

The expression of 5alpha-reductase types 1 and 2 was examined in human breast carcinoma using immunohistochemistry and RT-PCR. Immunoreactivity for 5alpha-reductase isozymes was also correlated with various clinicopathological parameters to examine possible local regulatory mechanisms of sex steroids, including progesterone and androgens, in human breast carcinoma tissues. Immunoreactivity for 5alpha-reductase type 1 was detected in the cytoplasm and possibly in the nuclear membrane of tumor cells in 35 of 60 invasive ductal carcinomas (58%), and type 2 signal was detected in 9 of these 60 cases (15%). The results from RT-PCR (n = 8) were consistent with those from immunohistochemistry. A significant positive correlation was detected between 5alpha-reductase type 1 immunoreactivity and androgen and progesterone receptor A or B labeling indexes, and immunoreactivities of 5alpha-reductase type 2, 17beta-hydroxysteroid dehydrogenase type 5, or 3beta-hydroxysteroid dehydrogenase, which recognizes both types I and II. An inverse correlation was detected between 5alpha-reductase type 1 immunoreactivity and tumor size, histological grade, or Ki-67 labeling index. 5alpha-Reductase type 2 immunoreactivity was significantly correlated with 17beta-hydroxysteroid dehydrogenase type 5 immunoreactivity, but not with other parameters. This study suggests that 5alpha-reductase type 1 is mainly expressed in human breast carcinoma, which may play an important role in the in situ production and actions of the potent androgen, 5alpha-dihydrotestosterone, including inhibition of cancer cell proliferation, in hormone-dependent human breast carcinoma.

17-Hydroxysteroid Dehydrogenases↗

PubMed2001

Retinoid receptors in the human endometrium and its disorders: a possible modulator of 17 beta-hydroxysteroid dehydrogenase.

Retinoids have recently been proposed to modulate estrogenic actions in various sex steroid-dependent neoplasms, but little has been studied in human endometrial disorders. Therefore, in this study, we first examined the immunolocalization of retinoic acid receptor alpha, beta, and gamma, and retinoid X receptor (RXR) alpha, beta, and gamma in 20 normal cycling human endometria, 34 endometrial hyperplasia, and 46 endometrioid endometrial adenocarcinomas. We then correlated these findings with other clinicopathological parameters, especially in the correlation between retinoid receptor subtypes and the status of steroid hormone receptors, 17 beta-hydroxysteroid dehydrogenase (17 beta-HSD) and aromatase. We also then examined the effects of retinoic acid on the expression of 17 beta-HSD type 2 in cell lines derived from endometrial carcinoma using Northern blotting analysis to examine the possible roles of retinoids in in situ endometrial estrogen metabolism. Among these six retinoid receptors examined, RXR gamma immunoreactivity was exclusively detected in the epithelial cells of the secretory phase endometrium but not of the proliferative phase, which was well correlated with 17 beta-HSD type 2 immunolocalization. However, in endometrial hyperplasia, RXR gamma was not correlated with 17 beta-HSD type 2. In endometrioid endometrial adenocarcinoma, there was a statistically significant correlation between 17 beta-HSD type 2 immunoreactivity and RXR gamma labeling index (LI) (P < 0.001) and between RXR gamma LI and progesterone receptor LI (r = 0.501, P = 0.003). A significant inverse correlation was also detected between RXR gamma LI and patient age (r = 0.449, P = 0.015). No statistically significant correlation was obtained between LIs of receptors and other clinicopathological parameters including the status of intratumoral aromatase examined by immunohistochemistry. In the endometrial carcinoma cell line, RL95-2, retinoic acid markedly increased the level of 17 beta-HSD type 2 messenger RNA in a time- and dose-dependent manner. These results all suggest that retinoic acids may be involved in modulation of in situ estrogen metabolism in both normal and neoplastic human endometrium possibly through RXR gamma by stimulating the expression of 17 beta-HSD type 2.

17-Hydroxysteroid Dehydrogenases↗

PubMed2001

Discerning malignancy in resected adrenocortical neoplasms.

Differential diagnosis between adenoma and carcinoma in resected human adrenocortical neoplasms may be one of the most problematic and difficult areas of surgical pathology practice. This is especially true in cases of relatively small adrenocortical tumors not associated with obvious signs of malignancy such as necrosis and/or hemorrhage. In addition, the numbers of these small adrenocortical neoplasms are increasing owing to the widespread application of sophisticated computed tomography and/or magnetic resonance imaging scans. No single parameter can be effective in this differential diagnosis of resected adrenocortical tumor. Histopathologic evaluation using a multivariate scoring system is considered most effective in discerning malignancy and biologic behavior of resected adrenocortical neoplasms. Molecular and cellular findings of adrenocortical carcinoma have been inconsistent except for the increased cell proliferation associated with adrenocortical malignancy. Therefore, an assessment of neoplastic cell proliferation using immunostains of cell cycle-associated nuclear antigen such as Ki-67 is the only useful auxiliary method of evaluating malignancy in resected adrenocortical neoplasms at present.

Adrenal Cortex Neoplasms↗

PubMed2001

Involvement of granule-mediated apoptosis in the cyclic changes of the normal human endometrium.

Our objective is to investigate the involvement of granule-mediated apoptosis in the cyclic changes of the endometrium. We demonstrated the localization of CD56, perforin, granzyme B and caspase-3 in the endometrium by immunohistochemistry. We also confirmed the localization of perforin by immuno-electron microscopy, and demonstrated apoptosis in endometrial glandular cells by TdT-mediated dUTP-biotin nick end labeling (TUNEL) and electron microscopy. Uterine CD56-positive natural killer (NK) cells expressed perforin and granzyme B in its cytoplasm. Uterine NK cells increased significantly in the endometrial stroma during the secretory phase, and peaked during the late secretory phase. These cells started decreasing in number during the menstrual period. In endometrial glandular cells, caspase-3 and TUNEL-positive cells increased significantly from the late secretory phase, with apoptosis reaching a peak during the menstrual period. Using electron microscopy, we observed uterine NK cells with chromatin rich, segmented nuclei and intracytoplasmic granules in the stroma obtained from late secretory phase endometria. These cells extended projections to the lining of endometrial glandular cells and attached to form a cell-to-cell contact. In addition, nuclear chromatin was observed to have already cohered and small cytoplasmic organelles were beginning to disappear, suggesting that these endometrial glandular cells were undergoing apoptosis. Utilizing immuno-electron microscopy, intracytoplasmic granules in uterine NK cells were stained with anti-perforin antibody. The findings of this study suggest that granule-mediated apoptosis in endometrial glandular cells induced by NK cells expressing perforin and granzyme B may be associated with the onset of menstruation.

Adult↗

PubMed2001

[Traumatic diaphragmatic herniation after continuous thoracic drainage: a case report].

We report a case of traumatic diaphragmatic hernia (TDH) resulting from continuous thoracic drainage and was successfully treated by surgical procedures. A 45-year-old man was admitted to our department due to shock after a blunt trauma by a traffic accident. As he revealed left hemothorax on admission, continuous thoracic drainage was performed. Soon after the drainage, diaphragmatic hernia occurred as an incarceration of the spleen into the thoracic cavity. In the literature, 80 cases with TDH have been reported in Japan since 1986. The purpose of this study is to discuss the mechanism of TDH in the acute phase and to consider its appropriate diagnostic tools. The following two results were obtained. (1) TDH may be appeared during the clinical course, especially after a continuous thoracic drainage, in patients with damaged diaphragm by blunt traumas. (2) CT is the most effective tool for the diagnosis of TDH.

Drainage↗

PubMed2001

17 beta-Hydroxysteroid dehydrogenase type 2 expression and enzyme activity in the human gastrointestinal tract.

The 17 beta-hydroxysteroid dehydrogenases (17 beta HSDs) play an important role in the regulation of intracellular levels of biologically active sex steroid hormones in various human tissues. To date, eight distinctive 17 beta HSD enzymes have been cloned and characterized in humans. Among these isoenzymes, 17 beta HSD type 2 (17 beta HSD2) catalyses the conversion of testosterone into androstenedione and/or oestradiol into oestrone in various tissues, and it has thus been suggested to be involved in the biological inactivation of these sex steroids. The human gastrointestinal tract and liver are considered as the principle sites of inactivation and metabolism of various forms of orally administered sex steroids. We therefore examined 17 beta HSD2 expression and activity in human adult non-pathological gastrointestinal tract in order to clarify further the biological significance of this enzyme. A total of 80 specimens (40 from males and 40 from females) of normal oesophageal, stomach, duodenal, ileal, colonic and rectal tissues were examined for immunohistochemistry. Altogether, 17 tissue specimens were used for enzyme assay, and eight for RNA analysis. 17 beta HSD2 activity was detected in the stomach, duodenum, ileum, colon and rectum. 17 beta HSD2 mRNA was most abundant in the small intestine. 17 beta HSD2 immunoreactivity was localized almost exclusively to the absorptive epithelium, which may be involved in the inactivation of excessive endogenous and exogenous active sex steroids. Results from the present study thus suggest that the human gastrointestinal tract is an important sex steroid metabolizing organ in humans.

17-Hydroxysteroid Dehydrogenases↗

PubMed2001

The vaso-contractile action of zooxanthellatoxin-B from a marine dinoflagellate is mediated via Ca2+ influx in the rabbit aorta.

We previously showed that zooxanthellatoxin-B, isolated from dinoflagellate, caused a sustained contraction of the aorta in an external Ca2+-dependent manner. To clarify the role of Ca2+ in this action, we examined the effects of zooxanthellatoxin-B as well as a depolarizing stimulus (60 mM KCl), using the simultaneous recording for cytosolic Ca2+ level (fura-2) and developed tension in the rabbit aorta. KCl (60 mM) elicited a rapid cytosolic Ca2+ elevation followed by a pronounced contraction, and time required for half-maximum contraction was 2 min. Zooxanthellatoxin-B caused an increase in cytosolic Ca2+ followed by a gradual contraction, with a time for half-maximum contraction of 5-10 min in a concentration-dependent manner. We found a strong correlation between Ca2+ elevation and the contraction in zooxanthellatoxin-B action. In a Ca2+-free solution, zooxanthellatoxin-B caused neither the contraction nor the increase in cytosolic Ca2+. Furthermore, both pre- and post-treatment with verapamil, a voltage-operated Ca2+-channel blocker, partially suppressed both an increase in cytosolic Ca2+ and the contraction by zooxanthellatoxin-B. Zooxanthellatoxin-B-induced contraction was also inhibited by other voltage-operated Ca2+-channel blockers: nifedipine or diltiazem. These results suggest that zooxanthellatoxin-B-elicited contraction is caused by a Ca2+ influx into the smooth muscle cells, partially via voltage-operated Ca2+ channels.

Animals↗

PubMed2001

Modification of urinary secretion of 8-hydroxy-2'-deoxyguanosine and serum ACTH concentration following repetitive parabolic flights.

It is important to clarify the molecular mechanisms of physiological responses of the human body to changes in gravity. Previous reports demonstrated that gravity-changing stress increases the human urinary concentration of 8-hydroxy-2'-deoxyguanosine (8-OHdG). However, it has yet to be clarified whether repetitive parabolic flight modulates the urinary concentration of 8-OHdG after exposure to gravity-changing stress. In the present study, the effects of the number of previous experiences with parabolic flight on urinary excretion of 8-OHdG and concentration of serum ACTH were examined in 12 healthy volunteers.

8-Hydroxy-2'-Deoxyguanosine↗

PubMed2000

Identification and functional characterization of a novel subtype of neuromedin U receptor.

Neuromedin U is a bioactive peptide isolated originally from the porcine spinal cord. We recently identified neuromedin U as the cognate ligand for the orphan G protein-coupled receptor FM-3. In this study, we isolated cDNA coding for a novel G protein-coupled receptor, TGR-1, which was highly homologous with FM-3. We found that neuromedin U specifically and clearly elevated the extracellular acidification rates, arachidonic acid metabolite release, and intracellular Ca(2+) mobilization in Chinese hamster ovary cells expressing TGR-1. Radiolabeled neuromedin U specifically bound with high affinity to membrane fractions prepared from these cells. These results show that TGR-1, like FM-3, is a specific and functional receptor for neuromedin U. We analyzed TGR-1 mRNA tissue distribution in rats using quantitative reverse transcription-polymerase chain reaction and found it to considerably differ from that of FM-3 mRNA. TGR-1 mRNA was primarily expressed in the uterus, suggesting that TGR-1 mediates the contractile activity of neuromedin U in this tissue. The identification of specific and functional receptor subtypes for neuromedin U will facilitate the study of their physiological roles and the search for their specific agonists and antagonists.

Amino Acid Sequence↗

PubMed2000

N-methyl-D-aspartate receptor subtype 2C is not involved in circadian oscillation or photoic entrainment of the biological clock in mice.

Ishida et al. [1994: Neurosci Lett 166: 211-215] reported the circadian change of N-methyl-D-aspartate (NMDA) receptor subtype 2C mRNA and photic induction of this receptor's mRNA in the suprachiasmatic nucleus (SCN). Therefore, we investigated the role of NMDA receptor subtypes in the biological clock using NMDA receptor 2A (NR2A)- or 2C (NR2C)-deficient mice. However, NR2C-/- mice showed normal light-dark (LD)-entrained locomotor activity rhythms and free-running rhythms under constant darkness and also exhibited normal reentrainment to 6-hr LD shifts and phase delays with single light pulses. Thus, present results demonstrated no significant NR2C contribution to circadian oscillation and photic entrainment, even though expression of NR2C mRNA was highly observed in the SCN. On the other hand, the period of the free-running activity rhythm in NR2A-/- mice but not NR2C-/- mice was slightly longer than that in wild-type mice in spite of low expression of NR2A in the SCN. Furthermore, reentrainment to an LD advance in NR2A-/- mice was slower under low-intensity light conditions. Thus, we suggest that NR2A plays a role in determining the behavioral state that affects the circadian rhythm. In order to elucidate the role of NR2A and NR2C in the SCN, we examined NMDA-induced Ca(2+) elevations in the SCN of mutant mice using a Ca(2+) imaging method. A partial reduction in Ca(2+) elevation was observed in both NR2A-/- and NR2C-/- mice when high concentrations (100 or 300 microM) of NMDA were applied. The present results suggest that NR2A plays a weak role in oscillation or entrainment of the biological clock, and that NR2C does not participate in the functions of circadian oscillation and light entrainment.

Animals↗

PubMed2000

Search for UV-responsive genes in human cells by differential mRNA display: involvement of human ras-related GTP-binding protein, Rheb, in UV susceptibility.

The search for genes responsible for the sensitivity of human cells to cell-killing effects of UV is an important area of biological research. To identify candidate genes responsible for UV sensitization, levels of mRNA expression were compared between UV-sensitive RSa cells and UV-resistant variant UV(r)-1 cells, using a differential display method and Northern blot analysis. Messenger RNA expression levels of human Ras homologue enriched in brain (Rheb) and/or a Rheb-like gene were up-regulated and slightly decreased in UV-irradiated RSa and UV(r)-1 cells, compared to in mock-irradiated cells, respectively. RSa and UV(r)-1 cells, both of which were treated with antisense oligonucleotides for Rheb RNA, exhibited an increased resistance to UV cell-killing. It remains unclear why UV(r)-1 cells are resistant to UV yet express Rheb mRNA at high levels. However, the results of antisense experiments together with the up-regulation in UV-irradiated RSa cells, suggest that Rheb is involved in the UV sensitization of both cells to UV cell-killing.

Cell Death↗

PubMed2000

Nonphotic entrainment by 5-HT1A/7 receptor agonists accompanied by reduced Per1 and Per2 mRNA levels in the suprachiasmatic nuclei.

In mammals, the environmental light/dark cycle strongly synchronizes the circadian clock within the suprachiasmatic nuclei (SCN) to 24 hr. It is well known that not only photic but also nonphotic stimuli can entrain the SCN clock. Actually, many studies have shown that a daytime injection of 8-hydroxy-2-(di-n-propylamino) tetralin (8-OH DPAT), a serotonin 1A/7 receptor agonist, as a nonphotic stimulus induces phase advances in hamster behavioral circadian rhythms in vivo, as well as the neuron activity rhythm of the SCN in vitro. Recent reports suggest that mammalian homologs of the Drosophila clock gene, Period (Per), are involved in photic entrainment. Therefore, we examined whether phase advances elicited by 8-OH DPAT were associated with a change of Period mRNA levels in the SCN. In this experiment, we cloned partial cDNAs encoding hamster Per1, Per2, and Per3 and observed both circadian oscillation and the light responsiveness of Period. Furthermore, we found that the inhibitory effect of 8-OH DPAT on hamster Per1 and Per2 mRNA levels in the SCN occurred only during the hamster's mid-subjective day, but not during the early subjective day or subjective night. The present findings demonstrate that the acute and circadian time-dependent reduction of Per1 and/or Per2 mRNA in the hamster SCN by 8-OH DPAT is strongly correlated with the phase resetting in response to 8-OH DPAT.

8-Hydroxy-2-(di-n-propylamino)tetralin↗

PubMed2000

Postnatal development of a GABA deficit and disturbance of neural functions in mice lacking GAD65.

The 65-kDa isoform of glutamic acid decarboxylase (GAD65) is believed to play an essential role for GABA synthesis in the central nervous system. Using mice with targeted disruption of the GAD65 gene (GAD65(-/-) mice) we investigated the contribution of GAD65 to GABA synthesis in different brain areas during postnatal development and in adulthood. In the amygdala, hypothalamus and parietal cortex of GAD65(+/+) mice an increase of GABA levels was observed during postnatal development, most prominently between the first and second month after birth. This increase appeared to be dependent on GAD65, as it was delayed by 2 months in GAD65(+/-) mice and was not observed in GAD65(-/-) mice. Likely as a consequence of their GABA deficit, adult GAD65(-/-) mice showed a largely abnormal neural activity with frequent paroxysmal discharges and spontaneous seizures. They furthermore displayed increased anxiety-like behaviour in a light/dark avoidance test and reduced intermale aggression, as well as a reduced forced-swimming-induced immobility indicative of an antidepressant-like behavioural change. Adult GAD65(+/-) mice did not show behavioural disturbances except for a reduced aggressive behaviour that was comparable to that in GAD65(-/-) mice. We conclude that GAD65-mediated GABA synthesis may be crucially involved in control of emotional behaviour and indispensable for a tonic inhibition that prevents the development of hyperexcitability in the maturating central nervous system. Aggressive, and possibly other social behaviour may be especially prone to regulation through GAD65-mediated GABA synthesis.

Age Factors↗