Shozo Tomonaga

Intracerebroventricular injection of l-serine analogs and derivatives induces sedative and hypnotic effects under an acute stressful condition in neonatal chicks

Four experiments were conducted to clarify the central functions of L-serine and its analogs on an acute stressful condition. Intracerebroventricular (i.c.v.) injection of L-serine (0.21, 0.42 and 0.84 micromol) attenuated stress responses in a dose-dependent fashion, as well as induced sleep, in Experiment 1. The effects of L- and D-serine in Experiment 2, those of L-serine, phosphoserine, acetylserine and L-cysteine in Experiment 3 and those of L-serine, glycine and lysophosphatidylserine in Experiment 4 were compared at an equimolar basis (0.84 micromol). D-Serine, proposed as an endogenous agonist of N-methyl-D-aspatate (NMDA) receptor, did not have sedative and hypnotic effects as observed with L-serine. In contrast, all the analogs and derivatives of L-serine had a sedative effect, although with a different manner in several behavioral markers of stress such as spontaneous activity and distress vocalizations. No significant changes in plasma corticosterone concentration were observed in any experiment. Taken together, the i.c.v. injection of L-serine analogs and its derivatives have sedative and hypnotic effects under an acute stressful condition, which does not involve the hypothalamic-pituitary-adrenal axis. In conclusion, L-serine may be effective in improving anxiety or sleep disorders induced by psychological stressor.

Intracerebroventricular injection of L-arginine induces sedative and hypnotic effects under an acute stress in neonatal chicks.

Summary.l-Arginine participates in many important and diverse biochemical reactions associated with the normal physiology of the organism. In the present study, we investigated the effect of central administration of l-arginine on the stress response and its mechanism in neonatal chicks. Intracerebroventricular (i.c.v.) injection of l-arginine clearly attenuated the stress response in a dose-dependent manner, and induced sleep-like behavior during 10u2009min. To clarify the mechanism by which l-arginine induces sedative and hypnotic effects in chicks, we investigated the effects of nitric oxide (NO) synthase (NOS) inhibitors on l-arginine-induced sedative and hypnotic effects, and as well as the effects of a NO donor. l-Arginine-induced (1.9u2009µmol) sedative and hypnotic effects were attenuated by i.c.v. co-injection with a non-selective NOS inhibitor NG-nitro-l-arginine methyl ester HCl (400u2009nmol). In addition, the effects of l-arginine were slightly attenuated by the inactive isomer of the NOS inhibitor NG-nitro-d-arginine methyl ester HCl (400u2009nmol). The i.c.v. injection of 3-morpholinosylnomine hydrochloride, a spontaneous NO donor, had little effect on postures. The i.c.v. injection of l-arginine had no effect on NOx concentration at various brain sites. These results suggested that the contribution of NO generation via NOS may be low in the sedative and hypnotic actions of l-arginine. Therefore, l-arginine and/or its metabolites, excluding NO, may be necessary for these actions.

Carnosine-induced antidepressant-like activity in rats

Depression is a pathological state of mood and is considered as one of the major causes of disabilities. Thus, the prevention of depression and care for individuals with depression is important. In the present study, we examined whether a single oral dose of CBEX (chicken breast extract), or carnosine (one of the major components of CBEX) affects immobility time, an index of depressive-like behavior, in the forced swimming test in male Wistar rats. CBEX tended to (P=0.09) and carnosine significantly (P<0.05) decreased immobility time in the forced swimming test. In the hippocampus, both CBEX and carnosine significantly decreased 3-methoxy-4-hydroxyphenylglycol, a major metabolite of norepinephrine, indicating that CBEX and carnosine could reduce NE activity in the hippocampus in the forced swimming test. CBEX and carnosine did not affect total locomotive distance or rearing in the open field test, suggesting that the reductions of immobility time by both treatments in the forced swimming test were not merely due to the stimulation of general motor activity. Taken together, these results suggest that CBEX has an antidepressant-like effect, which may be due, in part, to the effect of carnosine.

Central l-arginine reduced stress responses are mediated by l-ornithine in neonatal chicks

Summary.Recently, we observed that central administration of l-arginine attenuated stress responses in neonatal chicks, but the contribution of nitric oxide (NO) to this response was minimal. The sedative and hypnotic effects of l-arginine may be due to l-arginine itself and/or its metabolites, excluding NO. To clarify the mechanism, the effect of intracerebroventricular (i.c.v.) injection of l-arginine metabolites on behavior under social separation stress was investigated. The i.c.v. injection of agmatine, a guanidino metabolite of l-arginine, had no effect during a 10u2009min behavioral test. In contrast, the i.c.v. injection of l-ornithine clearly attenuated the stress response in a dose-dependent manner, and induced sleep-like behavior. The l-ornithine concentration in the telencephalon and diencephalon increased following the i.c.v. injection of l-arginine. In addition, several free amino acids including L-alanine, glycine, l-proline and l-glutamic acid concentrations increased in the telencephalon. In conclusion, it appears that l-ornithine, produced by arginase from l-arginine in the brain, plays an important role in the sedative and hypnotic effects of l-arginine observed during a stress response. In addition, several other amino acids having a sedative effect might partly participate in the sedative and hypnotic effects of l-arginine.

Oral administration of chicken breast extract increases brain carnosine and anserine concentrations in rats

Abstract Carnosine (β-alanyl-L-histidine) and its derivative anserine (β-alanyl-1-methyl-L-histidine) are antioxidants and putative neurotransmitters in the brain. These dipeptides are rich in the commercially available supplement chicken breast extract (CBEX). To clarify the effects of CBEX on the brain, we examined whether single oral administration of CBEX (20 ml/kg) affects brain dipeptide and free amino acid concentrations in male Wistar rats. CBEX significantly and time-dependently increased carnosine and anserine levels in the plasma (at 120 min after injection, increase rates were 2976 and 4142%, respectively), hippocampus (64 and 78%), and hypothalamus (188 and 120%), but not in cerebral cortex. Significant and time-dependent increases in citrulline in the hippocampus (49%) and hypothalamus (41%) demonstrated generation of nitric oxide due to the increased carnosine and/or anserine levels in these brain regions. These findings suggest that CBEX modifies brain functions by increasing levels of these dipeptides.

Intracerebroventricular injection of glutathione and its derivative induces sedative and hypnotic effects under an acute stress in neonatal chicks

Glutathione-related enzymes glyoxalase 1 and glutathione reductase 1 regulates anxiety in mice. To clarify the central function of glutathione as a neurotransmitter in the stress reaction, the effect of intracerebroventricular (i.c.v.) injection of reduced (GSH) (0.5, 1, 2 micromol) and oxidized (GSSG) glutathione (0.25, 0.5, 1 micromol) were investigated under an isolation-induced stress in the neonatal chick. Both GSH and GSSG dose-dependently decreased distress vocalizations and induced sleep-like behavior in chicks under acute stressful conditions. However, which glutathione is actually responsible for inducing sleep was unclear since glutathione cycles between GSH and GSSG in which two tripeptides are linked by a disulfide bond. Therefore, the behavior of chicks was monitored following the i.c.v. injection of S-methylglutathione (SMG) (0.0625, 0.25, 1 micromol). SMG does not form a disulfide bond due to the methylation of the SH group of the cysteine moiety. SMG had similar effects as observed in GSH and GSSG. In conclusion, glutathione and its derivative have sedative and hypnotic effects, and might be effective in improving psychic stress such as anxiety.

Central administration of dipeptides, beta-alanyl-BCAAs, induces hyperactivity in chicks

BackgroundCarnosine (β-alanyl-L-histidine) is a putative neurotransmitter and has a possible role in neuron-glia cell interactions. Previously, we reported that carnosine induced hyperactivity in chicks when intracerebroventricularly (i.c.v.) administered. In the present study, we focused on other β-alanyl dipeptides to determine if they have novel functions.ResultsIn Experiment 1, i.c.v. injection of β-alanyl-L-leucine, but not β-alanyl-glycine, induced hyperactivity behavior as observed with carnosine. Both carnosine and β-alanyl-L-leucine stimulated corticosterone release. Thus, dipeptides of β-alanyl-branched chain amino acids were compared in Experiment 2. The i.c.v. injection of β-alanyl-L-isoleucine caused a similar response as β-alanyl-L-leucine, but β-alanyl-L-valine was somewhat less effective than the other two dipeptides. β-Alanyl-L-leucine strongly stimulated, and the other two dipeptides tended to stimulate, corticosterone release.ConclusionThese results suggest that central β-alanyl-branched chain amino acid stimulates activity in chicks through the hypothalamus-pituitary-adrenal axis. We named β-alanyl-L-leucine, β-alanyl-L-isoleucine and β-alanyl-L-valine as Excitin-1, Excitin-2 and Excitin-3, respectively.

Effects of in utero TPTCL Exposure on the Learned Behaviors of Mice after Birth

Abstract Takagi, S., Tomonaga, S., Ito, S., Oshima, Y., Honjo, T. and Furuse, M. 2007. Effects of in utero TPTCL exposure on the learned behaviors of mice after birth. J. Appl. Anim. Res., 31: 13–20. The open field test and the elevated plus-maze test were applied to investigate the effects of in utero triphenyltin chloride (TPTCL) exposure on learned behavior in ICR strain mice. During pregnancy mice (8-weeks-old) received daily oral administration of vehicle (corn oil) or TPTCL (0.9 and 9 mg/kg) for a period of up to 18 days. Plasma sex hormone concentrations, body weight and organ weights were not significantly changed and no external malformations were noted after TPTCL exposure in either dams or pups. However, a decrease in the number of animals completing pregnancy and the number of dams rearing pups normally was observed in the 9 mglkg TPTCL group. No behavioral effects of TPTCL treatment were observed in pups or dams in the two tests employed. Measurable levels of TPTCL were found in the brains of dams in the TPTCL dosage group, but not in the brains of their pups. These results indicated that the TPTCL dosages and treatment period used did not influence metabolism and/or learned behaviors in mice. However the possibility is suggested that TPTCL may have adverse effects on normal pregnancy and maternal behavior.

Effect of Centrally Administered Sphingomyelin on Food Intake and HPA Axis in Chicks

Abstract Emoto, F., Tomonaga, S., Tachibana, T., Denbow, D.M. and Furuse, M. 2006. Effect of centrally administered sphingomyelin on food intake and HPA axis in chicks. J. Appl. Anim. Res., 29: 91–96. Sphignomyelin (SM) is an abundant lipid in myelin and its metabolites are well recognized as bioactive substances. The aim of the present study was to investigate the functions of SM in the chick brain. Intracerebroventricular (ICV) injection of SM decreased food intake in chicks. No significant changes in plasma corticosterone, glucose, 5-hydroxytryptamine and 5-hydroxyindoleacetic acid were detected. Thus anorexia caused by SM injection could be established but its mechanism could not be elucidated.