藤平 篤志

Recent studies have demonstrated that epigenetic modifications are deeply involved in neurogenesis; however, the precise mechanisms remain largely unknown. To determine the role of UTX (also known as KDM6A), a demethylase of histone H3K27, in neural development, we generated Utx-deficient mice in neural stem/progenitor cells (NSPCs). Since Utx is an X chromosome-specific gene, the genotypes are sex-dependent; female mice lose both Utx alleles (UtxΔ/Δ ), and male mice lose one Utx allele yet retain one Uty allele, the counterpart of Utx on the Y chromosome (UtxΔ/Uty ). We found that UtxΔ/Δ mice exhibited fetal ventriculomegaly and died soon after birth. Immunofluorescence staining and EdU labeling revealed a significant increase in NSPCs and a significant decrease in intermediate-progenitor and differentiated neural cells. Molecular analyses revealed the downregulation of pathways related to DNA replication and increased H3K27me3 levels around the transcription start sites in UtxΔ/Δ NSPCs. These results indicate that UTX globally regulates the expression of genes required for proper neural development in NSPCs, and UTX deficiency leads to impaired cell cycle exit, reduced differentiation, and neonatal death. Interestingly, although UtxΔ/Uty mice survived the postnatal period, most died of hydrocephalus, a clinical feature of Kabuki syndrome, a congenital anomaly involving UTX mutations. Our findings provide novel insights into the role of histone modifiers in neural development and suggest that UtxΔ/Uty mice are a potential disease model for Kabuki syndrome.

A non-narcotic anesthetic combination (Me/Mi/Bu) of medetomidine (Me), midazolam (Mi), and butorphanol (Bu) has been recommended as the injectable anesthesia in mice. An original dose of Me/Mi/Bu (0.3/4.0/5.0 mg/kg) has provided sufficient anesthetic duration of 40-50 min in mice. In addition, atipamezole is available for reversal of Me/Mi/Bu anesthesia. As an adverse effect of Me/Mi/Bu anesthesia, however, severe hypothermia has been also observed in mice. In the present study, we investigated 1) the main agent in Me/Mi/Bu to cause of hypothermia, 2) the effects of the differential doses of atipamezole on hypothermia induced by Me/Mi/Bu anesthesia and on the plasma levels of creatinine phosphokinase and transaminases, and 3) those recommended doses for preventing hypothermia induced by Me/Mi/Bu anesthesia in mice. The results suggested that 1) the α2-agonist medetomidine is most likely to induce hypothermia in mice under Me/Mi/Bu anesthesia, 2) the antagonism of atipamezole within proper dose range is effective in promoting the recovery from Me/Mi/Bu-induced hypothermia, and 3) Me/Mi/Bu at the recommended dose of 0.2/6.0/10.0 mg/kg enable to provide anesthetic effects for 40 min and is more considerable to prevent the hypothermia than that at the original dose of 0.3/4.0/5.0 mg/kg.

Hypothermia during anesthetic events is a common adverse effect of anesthesia in laboratory animals. In particular, small rodents such as mice is susceptible to hypothermia during anesthetic events. Therefore, the animals will need additional thermal support by external heating devices during and after anesthesia. In general, the time of recovery from anesthesia is typically longer in case of injectable anesthesia rather than inhalant anesthesia. However, the durations of thermal support have been almost limited to 1 hr from administration of anesthesia in general. Our study objectives are two-fold: 1) to compare the levels of hypothermia induced by injectable anesthesia with medetomidine-midazolam-butorphanol (MMB) and inhalant anesthesia with isoflurane (ISO); 2) to find the adequate durations of thermal support for preventing hypothermia induced by their anesthesia in mice. Adult male ICR mice were anesthetized during 40 min without and with the thermal support for 1 (both anesthetic groups), 2, 3, and 5 hr (in MMB group). Without thermal support, the decrease of body temperature in MMB group were more severe than that in ISO group. The durations of thermal support completely prevented hypothermia at 5 hr-support in MMB group and that at 1 hr-support in ISO group. However, the other short durations did not prevent hypothermia at 1, 2 and 3 hr-support in MMB group. These results suggest that the mice should be received thermal support over 5 hr after injection of MMB anesthesia to prevent hypothermia.

We investigated changes in cortisol (COR) concentration, which is well known as an index of stress in the serum of dairy cattle. The COR concentrations in serum obtained from dairy cattle were collected during practical training of first-year students on a farm attached to the Nippon Veterinary and Life Science University. Mean COR concentration in serum determined after practical training was significantly higher (P &lt 0.001) than that in serum collected before training. Discriminant analysis was used to classify the relation between COR concentration of serum collected before and after practical training. In conclusion, the data was bipartite according to the percentage of rise (rise rate) of COR concentration. Although the percentage of the rise was more than 300% in the high-rise-rate group, there was a significant negative correlation (P &lt 0.05) between age and COR concertation. It was thought that the high-rise-rate group has a chance to decrease stress after more experience. In contrast, the low-rise-rate group included 3 cattle indicating high COR concentration before and after practical training. Those 3 cattle were thought to be stressed easily. It is suggested that there was individual difference to stress.

Pentobarbital sodium (Somnopentyl) can induce surgical anesthesia with a strong hypnotic effect that causes loss of consciousness. Animals have been known to die during experimental surgery under anesthesia with Somnopentyl, causing it to be declared inadequate as a general anesthetic for single treatment. An anesthetic combination of 0.3 mg/kg medetomidine, 4.0 mg/kg midazolam and 5.0 mg/kg butorphanol (M/M/B:0.3/4/5) was reported to induce anesthesia for a duration of around 40 min in ICR mice; similar anesthetic effects were reported in both male and female BALB/c and C57BL/6J strains of mice. However, the anesthetic effects of this combination in Japanese field vole, Microtus montebelli, remain to be evaluated. In the present study, we assessed the effects of Somnopentyl and different concentrations of anesthetic combination (M/M/B:0.3/4/5, 0.23/3/3.75 or 0.15/2/2.5) in Japanese field voles, by means of anesthetic scores. We also examined effect of these anesthetics on production of offspring. Death of the animals was observed only with Somnopentyl. The anesthetic score of Somnopentyl was lower than those of the other anesthetics, although there were no significant differences in duration, body weight and frequency of respiratory among the evaluated anesthetics. Abortion rate with Somnopentyl was significantly higher than that with the M/M/B:0.23/3/3.75 combination, although there was no significant difference in the number of offspring between two. In conclusion, results of this study provide basic information for achieving appropriate anesthetic concentrations in addition to indicating a new, safe and effective surgical anesthetic for Japanese field voles.

Saliva as a sampling method is a low invasive technique for the detection of physiologically active substances, as opposed to sampling the plasma or serum. In this study, we obtained glucocorticoids transferred from the blood to the saliva from mice treated with 2.0 mg/kg via an intraperitoneal injection of cortisol. Next, to evaluate the effect of restraint stress using mouse saliva-collected under anesthesia by mixed anesthetic agents-we measured plasma and salivary corticosterone levels at 60 min after restraint stress. Moreover, to evaluate salivary corticosterone response to stress in the same individual mouse, an adequate recovery period (1, 3 and 7 days) after anesthesia was examined. The results demonstrate that exogenous cortisol was detected in the saliva and the plasma, in mice treated with cortisol. Restraint stress significantly increased corticosterone levels in both the plasma and saliva (P<0.001). Monitoring the results of individual mice showed that restraint stress significantly increased salivary corticosterone levels in all three groups (1-, 3- and 7-day recovery). However, the statistical evidence of corticosterone increase is stronger in the 7-day recovery group (P<0.001) than in the others (P<0.05). These results suggest that the corticosterone levels in saliva reflect its levels in the plasma, and salivary corticosterone is a useful, less-invasive biomarker of physical stress in mice. The present study may contribute to concepts of Reduction and Refinement of the three Rs in small animal experiments.

5-Hydroxytryptamine (5-HT) released from colonic mucosal enterochromaffin (EC) cells is a major signaling molecule, which participates in the pathophysiological regulation of colonic functions in gut disorder including irritable bowel syndrome (IBS), but the endogenous modulator system for the 5-HT release is not yet well elucidated. Our in vitro studies in guinea-pig colon have indicated that the cascade pathway of neuronal tachykinergic NK3 receptors and NK2 receptors on peptide YY (PYY)-containing endocrine L cells represents an endogenous modulator system for 5-HT release from EC cells and that melatonin, endogenous tachykinins and PYY play important roles in modulation of the release of 5-HT from EC cells via the endogenous NK2/NK3 receptor cascade system. This review aims at examining the potential role of the endogenous tachykinergic NK2/NK3 receptor cascade system controlling the release of 5-HT from EC cells, with special attention being paid to the pathophysiology of gut disorders including IBS.

5-Hydroxytryptamine ( 5-HT) released from colonic mucosal enterochromaffin ( EC) cells is a major signaling molecule, which participates in the pathophysiological regulation of colonic functions in gut disorder including irritable bowel syndrome ( IBS), but the endogenous modulator system for the 5-HT release is not yet well elucidated. Our in vitro studies in guinea-pig colon have indicated that the cascade pathway of neuronal tachykinergic NK3 receptors and NK2 receptors on peptide YY ( PYY)-containing endocrine L cells represents an endogenous modulator system for 5-HT release from EC cells and that melatonin, endogenous tachykinins and PYY play important roles in modulation of the release of 5-HT from EC cells via the endogenous NK2/NK3 receptor cascade system. This review aims at examining the potential role of the endogenous tachykinergic NK2/NK3 receptor cascade system controlling the release of 5-HT from EC cells, with special attention being paid to the pathophysiology of gut disorders including IBS.

The anorectic gut hormone, peptide YY (PYY), is released from colonic mucosal endocrine cells, but little is known about the role for tachykinin NK3 receptor in the control of PYY release from the colonic mucosa. We investigated the functional role for NK3 receptors in the control of PYY release from isolated guinea-pig distal colon, and the role for NK3 receptors-triggered PYY release in the control of colonic motility. Isolated colonic preparations were mounted in organ baths for measurement of PYY release and mechanical activity. The release of PYY from these preparations was determined by enzyme immunoassays. The NK3 receptor agonist senktide produced a tetrodotoxin/atropine-sensitive sustained increase in the release of PYY from the colonic preparations. Basal PYY release was transiently inhibited by the NK3 receptor antagonist SB222200. The neuropeptide Y1 receptor antagonist BIBO3304 produced a leftward shift of the concentration-response curves for senktide-evoked neurogenic contraction, but neither the neuropeptide Y2 receptor antagonist BIIE0246 nor the neuropeptide Y5 receptor antagonist CGP71683 affected the senktide concentration-response curves. NK3 receptors appear to play an important role in the control of PYY release from colonic mucosa, and NK3 receptor-triggered PYY release can exert Y1 receptor-mediated inhibition of tachykinergic neuromuscular transmission. This indicates a pathophysiological role for the NK3 receptor-triggered PYY release in the control of colonic motility.

The anorectic gut hormone, peptide YY (PYY), is released from colonic mucosal endocrine cells, but little is known about the role for tachykinin NK3 receptor in the control of PYY release from the colonic mucosa. We investigated the functional role for NK3 receptors in the control of PYY release from isolated guinea-pig distal colon, and the role for NK3 receptors-triggered PYY release in the control of colonic motility. Isolated colonic preparations were mounted in organ baths for measurement of PYY release and mechanical activity. The release of PYY from these preparations was determined by enzyme immunoassays. The NK3 receptor agonist senktide produced a tetrodotoxin/atropine-sensitive sustained increase in the release of PYY from the colonic preparations. Basal PYY release was transiently inhibited by the NK3 receptor antagonist SB222200. The neuropepticle Y-1 receptor antagonist BIB03304 produced a leftward shift of the concentration-response curves for senktide-evoked neurogenic contraction, but neither the neuropeptide Y-2 receptor antagonist B1100246 nor the neuropeptide Y-5 receptor antagonist CGP71683 affected the senkticle concentration-response curves. NK3 receptors appear to play an important role in the control of PYY release from colonic mucosa, and NK3 receptor-triggered PYY release can exert Y-1 receptor-mediated inhibition of tachykinergic neuromuscular transmission. This indicates a pathophysiological role for the NK3 receptor triggered PYY release in the control of colonic motility. (C) 2014 Elsevier B.V. All rights reserved.

We have suggested that intestinal microflora reduces the activity of the antioxidant enzyme superoxide dismutase (SOD) in the mouse cecal mucosa. In this study, gnotobiotic mice were used to examine the species of intestinal microflora influencing SOD activity in the cecal mucosa. The total SOD activity in the cecal mucosa of each germ-free (GF), gnotobiotic mouse with Escherichia coli, Lactobacillus and Bacteroides was significantly higher than that in the cecal mucosa of gnotobiotic mice with chloroform-treated feces (CHF), conventionalized (CVz) mice and conventional (CV) mice (P<0.05). In addition, CuZnSOD mRNA expression showed similar tendencies. Our results suggest that the antioxidant defense status in the cecal mucosa is influenced by CHF inoculation.

Superoxide dismutase (SOD) catalyzes the breakdown of superoxide into hydrogen peroxide and oxygen in the antioxidant defense system. We had reported that the SOD activities in the ceca of germ-free (GF) mice were significantly higher than those in conventional (CV) mice. In this study, we confirmed the location where SOD activity and protein expression increased in the ceca of GF mice. An immunohistochemical analysis and total SOD activity assay were conducted using the mucosa and other remaining tissues in the ceca. In addition to SOD activity in the ceca, 4 sites of intestinal (duodenal, jejunal, ileal and colonic) mucosae in GF mice were compared with those of CV mice. Total SOD activity in the cecal mucosa of GF mice was significantly higher than that in CV mice (P<0.01)and the intensity of CuZnSOD-positive cells in cecal mucosa was increased in all GF mice. Total and CuZnSOD activities in the duodenal, jejunal, ileal, cecal and colonic mucosae of GF mice were significantly higher than those in CV mice (P<0.05, or P<0.01). Furthermore, CuZnSOD mRNA showed similar tendencies with respect to these activities. Our results suggest for the first time that upregulation of SOD activity occurs in the entire intestinal mucosa of GF mice.

BACKGROUND AND PURPOSE The colon-derived peptide hormone, peptide YY (PYY), regulates colonic motility, secretion and postprandial satiety; but little is known about the influence of endogenous PYY on 5-HT release from colonic mucosa. Tachykinin NK2 receptor-selective agonist, beta Ala-NKA-(4-10) induces 5-HT release from guinea pig colonic mucosa via NK2 receptors on the mucosal layer. The present study was designed to determine the influence of endogenous PYY on 5-HT release from guinea pig colonic mucosa, evoked by the NK2 receptor agonist, beta Ala-NKA-(4-10). EXPERIMENTAL APPROACH Muscle layer-free mucosal preparations of guinea pig colon were incubated in vitro and the outflow of PYY or 5-HT and its metabolite, 5-HIAA, from these preparations were determined by enzyme immunoassays or HPLC with electrochemical detection respectively. KEY RESULTS beta Ala-NKA-(4-10) produced a tetrodotoxin-resistant sustained increase in the outflow of PYY and 5-HT from the mucosal preparations. The beta Ala-NKA-(4-10)-evoked 5-HT outflow was partially inhibited by Y1 receptor antagonist, BIBO3304, and Y2 receptor antagonist, BIIE0246, but with less potency. Exogenously-applied PYY also produced a sustained increase in the outflow of 5-HT that was inhibited by Y1 blockade but not Y2 blockade. CONCLUSION AND IMPLICATIONS Our findings support the view that the NK2 receptor-selective agonist, beta Ala-NKA-(4-10) produces a long-lasting PYY release from guinea pig colonic mucosa via NK2 receptors on L cells and beta Ala-NKA-(4-10)-evoked 5-HT release is in part mediated by endogenously released PYY, acting mainly on Y1 receptors on EC cells. The PYY-containing L cells appear to play a role in controlling the release of 5-HT from colonic EC cells.

It is known that pica, the consumption of non-nutritive substances such as kaolin, can be induced by administration of toxins or emetic agents in rats. In the present study, we examined the effects of intraperitoneal (i.p.) administration of cyclophosphamide on pica behavior and on the concentration of 5-hydroxyindoleacetic acids (5HIAA) in cerebrospinal fluid (CSF) in the following five strains of adult male rats: Sprague Dawley (SD), Wistar, Fischer 344 (F344), Wistar-Imamichi (WI) and Long Evans (LE). Cyclophosphamide (25 mg or 50 mg/kg) was injected (i.p.) into the rats and kaolin and food intake were measured at 24 hr after injection. The animals were anesthetized with urethane (1 g/kg) at 3 hr after injection of cyclophosphamide, and CSF was collected from the cisterna magna. WI and LE rats clearly showed pica behavior as compared with the other strains. In LE rats, the concentration of 5HIAA in CSF also increased in a dose-dependent manner of cyclophosphamide. The pretreatment with ondansetron (5-HT(3) antagonist) restored both changes (kaolin consumption and 5HIAA levels) induced by cyclophosphamide. These results suggest that the LE rat is sensitive to cyclophosphamide, that pica induced by cyclophosphamide mimics many aspects of emesis including the serotonergic response in the central nervous system and that use of the pica model would be a practical method for evaluating the effects of antiemetic drugs in addition to the mechanism of emesis.

BACKGROUND AND PURPOSE: Melatonin is involved in the regulation of colonic motility, and sensation, but little is known about the influence of melatonin on 5-hydroxytryptamine (5-HT) release from colonic mucosa. A tachykinin NK₂ receptor-selective agonist, [β-Ala⁸]-neurokinin A(4-10) [βAla-NKA-(4-10)] can induce 5-HT release from guinea pig colonic mucosa via NK₂ receptors on the mucosal layer. The present study was designed to determine the influence of melatonin on 5-HT release from guinea pig colonic mucosa, evoked by the NK₂ receptor agonist, βAla-NKA-(4-10). EXPERIMENTAL APPROACH: The effect of melatonin was investigated on the outflow of 5-HT and its metabolite 5-hydroxyindoleacetic acid (5-HIAA) from muscle layer-free mucosal preparations of guinea pig colon, using high-performance liquid chromatography with electrochemical detection. KEY RESULTS: Melatonin caused a sustained decline in the βAla-NKA-(4-10)-evoked 5-HT outflow from the muscle layer-free mucosal preparations, but failed to affect its metabolite 5-HIAA outflow. The specific MT₃ receptor agonist, 5-methoxycarbonylamino-N-acetyltryptamine mimicked the inhibitory effect of melatonin on βAla-NKA-(4-10)-evoked 5-HT outflow. A MT₃ receptor antagonist prazosin shifted the concentration-response curve of melatonin to the right in a concentration-dependent manner and depressed the maximum effect, but neither a combined MT₁/MT₂ receptor antagonist luzindole, nor a MT₂ receptor antagonist N-pentanoyl-2-benzyltryptamine modified the concentration-response curve to melatonin. CONCLUSIONS AND IMPLICATIONS: Melatonin inhibits NK₂ receptor-triggered 5-HT release from guinea pig colonic mucosa by acting at a MT₃ melatonin receptor located directly on the mucosal layer, without affecting 5-HT degradation processes. Possible contributions of MT₁/MT₂ melatonin receptors to the inhibitory effect of melatonin appear to be negligible. Melatonin may act as a modulator of excess 5-HT release from colonic mucosa.

The rdw rat is a hereditary hypothyroid strain isolated from Wistar-Imamichi rats. In the present study, adrenocorticotropic hormone (ACTH) and corticosterone responses to restraint stress (120 min) were examined in rdw adult male rats. ACTH response to restraint stress was higher in rdw rats than in hetero control rats. The plasma concentrations of corticosterone were lower in rdw rats than in control rats during the first 30 min after the onset of stress. Both ACTH and corticosterone responses to restraint stress in rdw rats recovered to control levels after thyroxine (T4) replacement therapy. These results suggest that hereditary hypothyroidism causes adrenal dysfunction directly and that hypersecretion of ACTH is a result of reduced corticosterone in rdw rats.

The effects of intracerebroventricular (i.c.v.) administration of pituitary adenylate cyclase activating polypeptide38 (PACAP38) on prolactin (PRL) secretion and the activity of tyrosine hydroxylase (TH) were examined in adult male and lactating rats with or without suckling stimulus. In adult male rats and lactating rats with suckling stimulus, administration of PACAP38 (0.25 or 1 nmol) decreased PRL secretion and increased the activity of TH in the stalk-median eminence. On the other hand, the injection of PACAP38 did not affect PRL secretion and TH activity in lactating rats without sucking stimulus. Administration of PACAP6-38 (4 nmol), a specific receptor antagonist, also had no effect on PRL secretion and TH activity in adult male rats. These results suggest that i.c.v. administration of PACAP inhibits PRL secretion mediated by dopamine neuron within the hypothalamus, but the effects of PACAP differ depending on the physiological condition of animals. These observed effects of PACAP on PRL release may be pharmacological responses rather than physiological responses.

The present study investigated whether pre-stimulation with intraperitoneal (i.p.) needling protects against development of diabetes in alloxan-treated transgenic (Tg) mice overexpressing the human Cu/Zn superoxide dismutase gene or non-Tg littermates of the FVB/N strain. Twenty minutes before the alloxan treatment (60 mg/kg) the mice were injected intraperitoneally with 0.05 ml saline while control mice received only the alloxan treatment. Hyperglycemic responses of the saline-injected mice to alloxan were significantly suppressed in the Tg mice (P<0.05). A similar reduction of response was also observed in non-Tg littermates, but the effect was less than that in the Tg mice. This protective effect on the diabetogenic action of alloxan was also demonstrated by an analysis of the number of days positive for urinary glucose, and by immunohistochemical analysis of pancreatic insulin-positive cells. A similar suppressive effect on the hyperglycemic response of alloxan was observed in the mice stimulated by i.p. needling alone. However, suppression of the hyperglycemic response was not observed in ICR mice receiving an i.p. injection. These results suggest that the diabetogenic action of alloxan can be suppressed by i.p. needling-mediated stimulation in mice that have a genetic background of the FVB/N strain. Since a slight protective effects of alloxan-induced diabetes was also observed in the Tg mice compared to FVB/N mice treated with only alloxan, this phenomenon could be more clearly seen in the Tg mice than in non-Tg littermates with an FVB/N background.

To investigate the androgenic effect of Kaempferia parviflora (KP), a Thai herbal plant, adult male rats were randomized into control and KP-treatment groups. Rats were treated orally with water in the control group and with 1,000 mg/kg/day of KP in the treatment group for 45 days. Blood samples were collected on days 10, 20, 30 and 45 for measurement of the serum follicle stimulating hormone (FSH), luteinizing hormone (LH), testosterone, progesterone and corticosterone levels. The reproductive and non-reproductive organs were dissected on day 45 and weighed. Mating behavior was also observed on days 20 and 30. Body weight was measured throughout the study period. The results showed that KP induced an increase in body weight compared with the controls. There were no significant differences in the weights of either reproductive (testis, seminal vesicle plus coagulating gland, levator ani muscle plus bulbocarvernosus muscle and glans penis, except the prostate gland) or non-reproductive organs (kidney, adrenal gland and gastracnemius muscle). There were no significant differences in serum levels of either FSH or LH between the two groups. The serum testosterone and progesterone levels were insignificantly lower in the KP group during the first 30 days. The serum corticosterone levels in the KP group were lower than those in the controls throughout the study period and were significantly low on days 20 and 30. There were no significant changes in mating behavior in the rats treated with KP. Although KP affected the body weight and serum corticosterone level, it did not affect mating behavior, reproductive and non-reproductive organ weights or hormones related to the reproductive system in the adult male rats. Therefore, we conclude that the testosterone-like effect of KP did not disturb the hypothalamic-pituitary-testicular axis or male reproduction.

Glutamate is the dominant excitatory neurotransmitter in a large number of physiological processes including neuroendocrine regulation. Some pharmacological studies have shown that different subtypes of glutamate receptor, such as the N-methyl-D-aspartic acid (NMDA) and alpha-amino-3-hydroxy-5-methy-4-isoxazolepropionic acid (AMPA) receptors, are involved in stress-induced adrenocorticotropin (ACTH) and prolactin secretion. However, the roles of the respective glutamate receptors and the mechanism of ACTH and prolactin secretion during stress via these receptors have not been investigated in detail. In the present study, we evaluated the role of AMPA-type glutamate receptor in ACTH and prolactin regulation under restraint stress in adult male rats. Male rats pretreated with a selective AMPA receptor antagonist, 2, 3-dihydroxy-6-nitro-7-sulfamoyl-benzo(f)quinoxaline (NBQX; 50 microg), through a lateral ventricle cannula were stressed by immobilization. Administration of NBQX inhibited ACTH and prolactin secretion in response to restraint stress. However, NBQX had no significant effects on the activity of tyrosine hydroxylase (TH), the rate-limiting enzyme in dopamine biosynthesis, as measured by the accumulation of 3, 4-dihydroxyphenylalanine (DOPA). In addition, administration of NBQX suppressed stress-induced prolactin secretion in the male rats pretreated with alpha-MT, an inhibitor of dopamine synthesis, and infused with dopamine solution (2.5 microg/200 microl/10 min). These results indicated that the effects of NBQX on prolactin secretion might be mediated by non-dopamine mechanisms. The contents of corticotropin-releasing hormone (CRH) and arginine vasopressin (AVP) in the median eminence (ME) of the male rats decreased during restraint stress; however, the fluctuations in CRH and AVP were eliminated by NBQX administration. These results suggest that stress-induced ACTH and prolactin release mediated by neurotransmission via AMPA receptors might be partly attributable to hypophysiotropic regulatory factors in the hypothalamus.

Previously, we demonstrated that plasma cortisol (Cor) levels were increased by road transportation in castrated male goats, but the extent of the increase was significantly reduced by 5alpha-dihydrotestosterone (DHT) implantation. This study aims to clarify whether the reduction of Cor secretion by androgen during transportation results from reduced plasma adrenocorticotropic hormone (ACTH). Castrated goats were implanted separately with cholesterol (Cho), testosterone (T) or DHT, followed by transportation. Plasma Cor levels increased during transportation regardless of hormone treatment, but the levels in T and DHT treated animals were lower than those in animals treated with Cho. Plasma ACTH levels also increased during transportation, and those in T treated animals were significantly lower than in those treated with Cho. However, plasma ACTH levels in DHT treated animals varied among the animals and did not differ from those in Cho treated animals. Significant and highly positive correlations between the logarithm of plasma ACTH levels and plasma Cor levels were found in every treatment group. The areas under the regression curves between plasma ACTH levels and plasma Cor levels associated with T and DHT treatments were significantly lower than those with Cho treatment. In conclusion, T was shown to reduce ACTH secretion in response to transportation in castrated goats. However, this suppression of the increase in Cor secretion during transportation by androgen is suggested to be mainly a result of suppression of the responsiveness of the adrenal cortex to ACTH.

Thyroid hormones permit the annual reproductive transition of seasonal breeders. Although, precise function of thyroid hormones in seasonal breeding is not well understood. In the present study, we examined effects of hypothyroidism on the hypothalamus-pituitary-gonadal axis in adult male golden hamsters after transition of the short-day photoperiod (SD; 8 h light: 16 h dark) condition. We confirmed that hypothyroid, which had been induced by administration of thiouracil in drinking water for 4 weeks, did not have direct effects on testes in male hamsters under the long-day photoperiod. Plasma concentrations of free T3 and T4 decreased 15 weeks after transition of SD condition. Plasma concentrations of testosterone in the hypothyroid group decreased earlier than in the control group after the transition from LD to SD. In animals treated with testosterone after castration, plasma concentrations of LH in the hypothyroid group decreased earlier than in the control group after the transition of SD. On the other hand, pituitary response to GnRH for LH release did not change in castrated hamsters as a result of hypothyroidism. These results suggest that thyroid hormones act the hypothalamus and might be required to maintain GnRH secretion in male golden hamsters.

The estrous cycle influence on the number of ovulated eggs after injection of pregnant mare serum gonadotropin (PMSG) and human chorionic gonadotropin (hCG) was investigated in 12, 18, and 24 weeks old adult female Wistar-Imamichi (WI) rats. PMSG (150 IU/kg) was injected at metestrus, diestrus, proestrus, or estrus, followed by hCG (75 IU/kg) 55 h later. Ovulation was induced at all ages and stages of the estrous cycle. The number of ovulated eggs was not affected by stage for similarly aged rats, however, the number of ovulated eggs obtained after treatment decreased with age. These results demonstrate that the PMSG/hCG treatment can induce ovulation at any stage of estrous cycle in WI rats and efficient superovulation at 12 weeks of age.

In order to clarify the functional relationship between thyroid, adrenal and gonadal hormones, hypothyroidism was induced by administration of thiuoracil in adult male and female rats, and the effects of hypothyroidism on the adrenal and the gonadal axes were investigated in the present study. 1. The functional relationship between thyroid and adrenal hormones: Adrenal weights and corticosterone were lowered, whereas the secretion of ACTH, corticotrophin-releasing hormone (CRH) and arginine vasopressin (AVP) increased in hypothyroid rats compared to euthyroid rats. These results indicate that hypothyroidism causes adrenal dysfunction directly and results in hypersecretion of CRH and AVP from the hypothalamus. 2. The functional relationship between thyroid and gonadal hormones: The pituitary response to LHRH was lowered, whereas the testicular response to hCG was not changed in hypothyroid rats. Hypothyroidism suppressed copulatory behavior in male rats. These results suggest that hypothyroidism probably causes dysfunction in gonadal axis at the hypothalamic-pituitary level in male rats. In adult female rats, hypothyroidism inhibited the follicular development accompanied estradiol secretion, whereas plasma concentrations of progesterone and prolactin (PRL) increased in hypothyroid female rats. Hypothyroidism significantly increased the pituitary content of vasoactive intestinal peptide (VIP) though it did not affect dopamine synthesis. These results suggest that hypothyroidism increases pituitary content of VIP and this increased level of VIP likely affects PRL secretion in a paracrine or autocrine manner. In female rats, inhibition of gonadal function in hypothyroid rats mediated by hyperprolactinemia in addition to hypersecretion of endogenous CRH.

In the present study, we used closed colony-Wistar-Imamichi (WI), inbred WI and Long Evans (LE) adult male rats to examine the secretion of ACTH and corticosterone in response to restraint stress. Blood (0.3 ml) was withdrawn through a jugular cannula at 0, 15, 30, 60 and 120 min after the onset of restraint stress. Plasma concentrations of ACTH and corticosterone increased after stress in all groups, but the responses of ACTH and corticosterone secretion were higher in LE rats than in WI rats. Present data suggest that the LE rat might be a good model as a high-response strain and the closed colony or the inbred WI rat might be a good model as a low-response strain in restraint stress experiments.

Hatano high- and low-avoidance (in a two-way active avoidance task) animals (HAA and LAA, respectively) were successfully selected from a Sprague-Dawley rat population. Pup growth of both strains was dependent on the maternal strain in a cross-fostering study. To determine whether there are strain-specific differences between HAA and LAA in maternal care, both strains of dams were subjected to a test battery as measured by nest building, home cage behavior, pup retrieval, and milk ejection tests. In addition, changes in plasma concentrations of lactotropic and corticotropic hormones such as prolactin, ACTH, and corticosterone were examined during lactation. The test battery indicated that the dams of both strains built good nests and spent an identical amount of time with their offspring. However, LAA dams showed a prolonged latency time for pup retrieval and often left pups outside the nest until the end of the test period. LAA dams also showed a decreased amount of milk ejection, whereas no strain differences were observed in milk ejection after oxytocin treatment. During lactation, a lesser increase in plasma concentrations of prolactin and a greater increase in ACTH were found in LAA dams. There were no differences between the two strains in plasma concentrations of corticosterone. These results clearly demonstrated decreases in maternal behavior and milk ejection in LAA as compared to HAA dams. The present results also suggest that maternal motivation and mechanisms responsible for maternal hormones related to suckling are involved in the degree of pup growth.