Central injection of oxytocin reduces food intake and affects hypothalamic and adipose tissue gene expression in chickens.

Oxytocin (OT) is a well-characterized neurotransmitter that participates in a wide range of physiological processes including the inhibition of food intake. The avian ortholog, mesotocin (MT), differs from OT by a single amino acid. Little is known regarding the function of OT in regulating energy balance in birds; thus, this study was designed to determine the effects of central OT injection on food intake and adipose tissue physiology in chicks. At 4-d post-hatch, broiler chicks were fasted for 3 h and injected intracerebroventricularly with 0 (vehicle), 0.63, 2.5, 5.0, or 10 nmol OT. Oxytocin decreased food and water intake during the entire 180-min observation period. The reduction in water intake was likely not prandial because chicks that were food restricted after OT injection also drank less. There was increased c-Fos immunoreactivity in several appetite-associated hypothalamic nuclei in OT-injected chicks at 1 h, including the arcuate (ARC), dorsomedial nucleus (DMN), lateral hypothalamus (LH), paraventricular nucleus (PVN), and ventromedial hypothalamus (VMH). OT treatment was associated with reduced hypothalamic corticotropin-releasing factor (CRF) mRNA and increased cloacal temperature at 1 h post-injection. We then investigated appetite- and adipose tissue-associated effects of OT in chicks from lines that have undergone long-term selection for either low (LWS) or high (HWS) juvenile body weight. Central injection of OT decreased food intake in both lines with the magnitude of response greater in the HWS than LWS chicks. Adipose tissue abundance of fatty acid-binding protein 4, monoglyceride lipase (MGLL), MT, and perilipin-1 mRNA was greater in LWS than HWS chicks. Lipoprotein lipase, MGLL, and MT mRNAs increased in response to OT injection in LWS but not HWS chicks. In conclusion, central injection of OT induced anorexia, reduced water intake, increased body temperature, and was associated with activation of the ARC, DMN, LH, PVN, and VMH in the hypothalamus. The effects on appetite and body temperature may involve CRF signaling in the hypothalamus and lipolysis in the adipose tissue, respectively. There were differences in the appetite, and adipose tissue response to OT in body weight-selected lines of chicks supports that MT plays a role in energy balance regulation in chickens.

Alpha-melanocyte stimulating hormone-induced anorexia in Japanese quail (Coturnix japonica) likely involves the ventromedial hypothalamus and paraventricular nucleus of the hypothalamus.

Alpha-melanocyte stimulating hormone (α-MSH) reduces food intake in birds and mammals. The objective of this experiment was to determine effects of α-MSH on food and water intake, and hypothalamic c-Fos immunoreactivity and appetite-associated factor mRNA in Japanese quail (Coturnix japonica), a species that has not undergone the same artificial selection for growth-related traits as the chicken. At 7days post-hatch, 3-h-fasted quail were intracerebroventricularly (ICV) injected into the lateral ventricle with 0 (vehicle), 0.5, 5, or 50pmol of α-MSH and food and water intake were recorded at 30min intervals for 180min. In the second and third experiment, quail were injected with 50pmol α-MSH and hypothalami were collected at 1h to determine c-Fos immunoreactivity and mRNA abundance, respectively. At 30min, quail injected with 5 or 50pmol of α-MSH ate and drank less than vehicle-injected quail. Quail injected with 50pmol ate less for the entire duration of the experiment and drank less than vehicle-injected quail for 120min post-injection. Hypothalamic expression of agouti-related peptide and DOPA decarboxylase were greater in vehicle- than α-MSH-injected quail, whereas melanocortin receptor 4 (MC4R) mRNA was greater in α-MSH- than vehicle-injected birds. Alpha-MSH injection was associated with more c-Fos immunoreactive cells in the ventromedial hypothalamus (VMH) and paraventricular nucleus (PVN) of the hypothalamus. Results suggest that the anorexigenic effect of α-MSH is conserved among avians and that effects in quail are associated with the VMH and PVN and involve MC4R.

Effects of intracerebroventricular injection of rosiglitazone on appetite-associated parameters in chicks.

Rosiglitazone, a thiazolidinedione, is a peroxisome proliferator-activated receptor gamma (PPAR-γ) agonist that increases insulin sensitivity. A documented side effect of this diabetes drug is increased appetite, although the mechanism mediating this response is unknown. To better understand effects on food intake regulation, we evaluated the appetite-associated effects of rosiglitazone in an alternative vertebrate and agriculturally-relevant model, the domesticated chick. Four day-old chicks received intracerebroventricular (ICV) injections of 0, 5, 10 or 20nmol rosiglitazone and food and water intake were measured. Chicks that received 5 and 10nmol rosiglitazone increased food intake during the 2h observation period, with no effect on water intake. In the next experiment, chicks were ICV-injected with 10nmol rosiglitazone and hypothalamus was collected at 1h post-injection for total RNA isolation. Real-time PCR was performed to measure mRNA abundance of appetite- and glucose regulation-associated factors. Neuropeptide Y (NPY) and proopiomelanocortin (POMC) mRNA decreased while NPY receptor 1 (NPYr1) mRNA increased in rosiglitazone-injected chicks compared to the controls. Results show that central effects of rosiglitazone on appetite are conserved between birds and mammals, and that increases in food intake might be mediated through NPY and POMC neurons in the hypothalamus.

Central Injection of Glucose Modifies Behavior, Amino Acid and Monoamine Metabolism in Neonatal Chicks under Acute Stressful Conditions.

The effect of intracerebroventricular (i.c.v.) injection of a wide range of glucose concentrations on the behavioral response, central amino acid and monoamine contents was investigated in chicks exposed to a social isolation stressful condition. The chicks were given an i.c.v. injection of 0.21, 0.42, 0.84, and 1.68 µmol of D-glucose, and then behavioral changes were observed over 10 min. The behavioral stress response was dose-dependently decreased and calm behavior was increased by i.c.v. administration of glucose. In the diencephalon, glutamine was positively correlated, whereas glycine was negatively correlated with the dose of glucose. In the telencephalon, the dopamine metabolite and dopamine turnover rates were positively correlated, whereas dopamine was negatively correlated with doses of glucose. In the plasma, isoleucine and hydroxyproline were positively correlated with the dose of glucose, and several amino acids were also influenced by glucose levels. These results suggest that the possible pathways of the sedative effect of glucose include: (1) amino acids synthesized from injected glucose, which can induce the sedative and/or hypnotic effects; (2) amino acids modified by injected glucose transported in the brain from the peripheral tissues; and (3) injected glucose-induced decreases in brain dopamine levels. In conclusion, these changes induced by central glucose interact and induce the sedative effect in neonatal chicks.

Comparison of centrally injected tryptophan-related substances inducing sedation in acute isolation stress-induced neonatal chicks.

In the present study, we first focused on the function of l-tryptophan (TRP) metabolites which are synthesized in different metabolic pathways, namely, the kynurenine (KYN) pathway and serotonin (5-HT) pathway during an acute isolation stress. When l-TRP metabolites were intracerebroventricularly injected on an equimolar basis (100 nmol), 5-HT induced a sedative effect in neonatal chicks. Additionally, plasma corticosterone, dopamine, 5-HT, and its metabolite 5-hydroxyindoleacetic acid concentrations were increased in the diencephalon of the 5-HT treated group compared with other groups. Second, the two doses (400 or 800 nmol) of l- and d-TRP were compared under a corticotrophin-releasing hormone-augmented social isolation stress. When comparing the efficacy between l- and d-TRP against stress behavior, both amino acids had a similar effect and quickly suppressed distress vocalizations. Finally, d-amino acid levels in the diencephalon and telencephalon were measured but d-TRP was not found. These results indicate that l- and d-TRP induce the same effect in attenuating stress but the mode of action of TRP derivatives, namely 5-HT differs during an acute isolation stress in neonatal chick. The absence of d-TRP in the diencephalon further suggests that instead of being an endogenous factor it may play role as a pharmacological factor.

Long-term consumption of dried bonito dashi (a traditional Japanese fish stock) reduces anxiety and modifies central amino acid levels in rats.

Dried bonito dashi, a traditional Japanese fish stock, enhances palatability of various dishes because of its specific flavor. Daily intake of dashi has also been shown to improve mood status such as tension-anxiety in humans. This study aimed at investigating beneficial effects of dashi ingestion on anxiety/depression-like behaviors and changes in amino acid levels in the brain and plasma in rats. Male Wistar rats were given either dried bonito dashi or water for long-term (29 days; Experiment 1) or single oral administration (Experiment 2). Anxiety and depression-like behaviors were tested using the open field and forced swimming tests, respectively. Concentrations of amino acids were measured in the hippocampus, hypothalamus, cerebellum, and jugular vein. During the long-term (29 days) consumption, rats given 2% dashi frequently entered the center zone and spent more time compared with the water controls in the open field test. However, the dashi was ineffective on depression-like behavior. In the hippocampus, concentrations of hydroxyproline, anserine, and valine were increased by dashi while those of asparagine and phenylalanine were decreased. In the hypothalamus, the methionine concentration was decreased. In a single oral administration experiment, the dashi (1%, 2% or 10%) showed no effects on behaviors. Significance was observed only in the concentrations of α-aminoadipic acid, cystathionine, and ornithine in the hippocampus. Dried bonito dashi is a functional food having anxiolytic-like effects. Daily ingestion of the dashi, even at lower concentrations found in the cuisine, reduces anxiety and alters amino acid levels in the brain.

Expression of carnitine palmitoyl-CoA transferase-1B is influenced by a cis-acting eQTL in two chicken lines selected for high and low body weight.

Carnitine palmitoyl-CoA transferase-1B is a mitochondrial enzyme in the fatty acid oxidation pathway. In a previous study, CPT1B was identified as differentially expressed in the hypothalamus of two lines of chickens established by long-term selection for high (HWS) or low (LWS) body weight. Mammals have three paralogs (CPT1a, b and c) while nonmammalian vertebrates only have two (CPT1A, B). CPT1A is expressed in liver and CPT1B in muscle. CPT1c is expressed in hypothalamus, where it regulates feeding and energy expenditure. We identified an intronic length polymorphism, fixed for different alleles in the two populations, and mapped the hitherto missing CPT1B locus in the chicken genome assembly, to the distal tip of chromosome 1p. Based on molecular phylogeny and gene synteny we suggest that chicken CPT1B is pro-orthologous of the mammalian CPT1c. Chicken CPT1B was differentially expressed in both muscle and hypothalamus but in opposite directions: higher levels in hypothalamus but lower levels in muscle in the HWS than in the LWS line. Using an advanced intercross population of the lines, we found CPT1B expression to be influenced by a cis-acting expression quantitative trait locus in muscle. The increased expression in hypothalamus and reduced expression in muscle is consistent with an increased food intake in the HWS line and at the same time reduced fatty acid oxidation in muscle yielding a net accumulation of energy intake and storage. The altered expression of CPT1B in hypothalamus and peripheral tissue is likely to be a mechanism contributing to the remarkable difference between lines.

Central administration of L- and D-aspartate attenuates stress behaviors by social isolation and CRF in neonatal chicks.

Intracerebroventricular (i.c.v.) administration of L-aspartate (L-Asp) attenuates stress responses in neonatal chicks, but the mechanism has not been clarified. In the present study, three behavioral experiments were carried out under socially isolated stressful conditions exacerbated by the use of corticotrophin-releasing factor (CRF). In Experiment 1, i.c.v. injection of L-Asp attenuated behavioral stress responses (distress vocalization and active wakefulness) in a dose-dependent manner. Furthermore, L-Asp increased time spent standing/sitting motionless with eyes open and sitting motionless with head dropped (sleeping posture) in comparison with the group receiving CRF alone. In Experiment 2, i.c.v. injection of D-Asp dose-dependently decreased the number of distress vocalizations and the amount of time spent in active wakefulness. D-Asp increased the time spent standing/sitting motionless with eyes open compared with the group receiving CRF alone. In Experiment 3, we directly compared the effect of L-Asp with that of D-Asp. Both L- and D-Asp induced sedative effects under an acutely stressful condition. However, L-Asp, but not D-Asp, increased the time spent in a sleeping posture. These results indicate that both L- and D-Asp, when present in the brain, could induce a sedative effect, while the mechanism for hypnosis in neonatal chicks may be different for L-Asp in comparison with D-Asp.

Orally administered L-ornithine reduces restraint stress-induced activation of the hypothalamic-pituitary-adrenal axis in mice.

In a previous study, we confirmed that orally administered L-ornithine can be transported into the brain of mice. In addition, orally administered L-ornithine, within a limited dose range, had an anxiolytic-like effect in the elevated plus-maze test. However, the mechanism by which orally administered L-ornithine reduced the stress response in mice is still unclear. Experiment 1 determined whether orally administered L-ornithine could reduce the stress-induced activation of hypothalamic-pituitary-adrenal axis. Mice were orally administered L-ornithine (0, 0.75, 1.5 and 3 mmol/10 ml/kg, p.o.), and restrained for 30 min from 30 min post administration. There was a significant decrease in the corticosterone levels in the group receiving 0.75 mmol of L-ornithine compared to the control group. In Experiment 2, the effect of orally administered L-ornithine (0 and 0.75 mmol/10 ml/kg, p.o.) on endogenous monoamine release was investigated using in vivo microdialysis. Only the monoamines metabolites 5-hydroxyindoleacetic acid (5-HIAA), dihydroxyphenylacetic acid (DOPAC) and homovallinic acids (HVA) were detected in the present study. Dialysate concentrations of 5-HIAA, DOPAC and HVA were not significantly changed immediately after administration of L-ornithine and restraint stress. In conclusion, changes of corticosterone concentrations by orally administered L-ornithine were not related to alterations in brain monoamine metabolisms.

Fasting of 3-day-old chicks leads to changes in histone H3 methylation status.

Unfavorable nutritional conditions during early developmental periods may cause neuronal network remodeling in the hypothalamus, which influences subsequent adaptability to those same stressful conditions. Alterations in hypothalamic plasticity as a result of neuronal remodeling are achieved by variations in the repertoire of proteins expressed via gene transcriptional activation or repression, both of which are modulated by histone methylation status. This study demonstrates that fasting had a stimulatory effect on dimethylation and trimethylation of histone 3 at lysine 27 (H3K27) in preoptic/anterior hypothalamus (PO/AH) of 3-day-old chicks. The expression of enhancer of zeste 2 (EZH2), a H3K27-specific histone methyltransferase (HMT), was significantly increased by fasting in the paraventricular nucleus (PVN) and PO/AH, which is consistent with the upregulation of H3K27 dimethylation and trimethylation. Furthermore, in the PVN, corticotrophin-releasing hormone (CRH) mRNA expression was significantly inhibited, while mRNA expressions of thyrotropin-releasing hormone (TRH) and type 2 deiodinase (D2) were significantly stimulated by fasting. These findings highlight the potential role of H3K27 methylation status in early feed stress responses in chicks and may be indicative of an epigenetic mechanism for later adaptation to feed intake stress.

Orally administered L-ornithine elevates brain L-ornithine levels and has an anxiolytic-like effect in mice.

Intracerebroventricular injection of L-ornithine has demonstrated sedative and hypnotic effects in neonatal chicks exposed to acute stressful conditions. However, whether orally administered L-ornithine can reduce acute mental stress remains to be defined. To clarify the nutritional importance of L-ornithine in controlling the stress response, in Experiment 1 we first investigated whether orally administered L-ornithine can be transported into the brain of mice. Mice were orally administered L-ornithine (3 mmol/water 10 ml/kg, per os). L-Ornithine levels were significantly elevated in the cerebral cortex and hippocampus at 30 and 60 minutes post-administration. In Experiment 2, the effect of orally administered L-ornithine (0, 0.1875, 0.75 and 3 mmol/water 10 ml/kg, per os) on anxiety-like behavior in mice exposed to the elevated plus-maze test was examined at 30 minutes post-administration. There was a significant increase in the percentage of time spent and entries in the open arms in the group receiving 0.75 mmol of L-ornithine compared to the control group. Furthermore, locomotion activity in a novel environment was not significantly changed between the control group and 0.75 mmol of L-ornithine group in Experiment 3. Therefore, it appears that orally administrated L-ornithine is bioavailable to the rodent brain and reduces anxiety-like behavior as demonstrated by the elevated plus-maze test.

Differentially expressed genes in hypothalamus in relation to genomic regions under selection in two chicken lines resulting from divergent selection for high or low body weight.

Long-term divergent selection for low or high body weight from the same founder population has generated two extremely divergent lines of chickens, the high- (HWS) and low-weight (LWS) selected lines. At selection age (56 days), the lines differ by more than nine times in body weight. The HWS line chickens are compulsive feeders, whereas in the LWS line, some individuals are anorexic and others have very low appetite. Previous studies have implicated the central nervous system and particularly the hypothalamus in these behavioural differences. Here, we compared the mRNA expression in hypothalamus tissue from chickens on day 4 post-hatch using oligonucleotide arrays and found that the divergent selection had resulted in minor but multiple expression differences. Differentially expressed genes were enriched in processes 'DNA metabolism, repair, induction of apoptosis and metabolism'. Several differentially expressed genes participate in the regulation of neuronal plasticity and development, including apoptosis, or are neurotransmittor receptor subtypes. Less change was seen when comparing hypothalamic neuropeptide mediators of appetite such as the melanocortin receptors. The genomic locations of these differentially expressed genes were then compared to the locations of growth QTLs and to a genome-wide map of chromosomal regions that have been under divergent selection between the lines. The results indicate which differentially expressed hypothalamic genes have responded to the divergent selection and that the results predict that it is more likely to find causative genes among these most differentially expressed genes. Because of such differential gene expression in hypothalamus, the lines may adapt behaviourally different particularly to the post-hatch situation when independent feeding to obtain energy is established.

AICAR and Compound C regulate food intake independently of AMP-activated protein kinase in lines of chickens selected for high or low body weight.

AMP-activated protein kinase (AMPK) functions to maintain cellular and body energy balance. Our aim was to investigate the effect of intracerebroventricular (ICV) administration of AMPK stimulator AICAR and AMPK inhibitor Compound C on food intake in lines of chickens that had undergone long-term selection from a common founder population for high (HWS) or low (LWS) body weight. AICAR caused a quadratic dose-dependent decrease in food intake in LWS but not HWS chicks. Compound C caused a quadratic dose-dependent increase in food intake in HWS but not in LWS chicks. Key aspects of the AMPK pathway, including upstream kinases mRNA expression, AMPK subunit α mRNA expression and phosphorylation, and a downstream target acetyl CoA carboxylase (ACC) phosphorylation were not affected by either AICAR or Compound C in either line. The exception was a significant inhibitory effect of AICAR on ACC phosphorylation ratio due to increased total ACC protein content without changing phosphorylated ACC protein levels. Thus, the anorexigenic effect of AICAR in LWS chicks and orexigenic effect of Compound C in HWS chicks resulted from activation or inhibition of other kinase pathways separate from AMPK. These results suggest genetic variation in feeding response for central AICAR and Compound C in chickens, which may contribute to the different body weights between the HWS and LWS lines.

Genetic selection for body weight in chickens has altered responses of the brain's AMPK system to food intake regulation effect of ghrelin, but not obestatin.

The effects of ghrelin and obestatin regulation of food intake are different in mammals and chickens. We investigated central effects of ghrelin and obestatin in lines of chickens selected 50 generations for high (HWS) or low (LWS) body weight. We hypothesized that the effect of ghrelin and obestatin on food intake in 5-day-old chicks is mediated by the AMP-activated protein kinase (AMPK) system and selection for body weight alters the brain's response to ghrelin and obestatin by changing the neuronal AMPK system. Although intracerebroventricular (ICV) ghrelin injection decreased food intake in both lines, the threshold for the anorexigenic effect of central ghrelin was lower in LWS than HWS chicks. Obestatin caused a linear dose-dependent increase in food intake in HWS but not LWS chicks. ICV injection of 0.4 nmol ghrelin inhibited hypothalamic AMPK related gene expression and phosphorylation of AMPK α and acetyl-CoA carboxylase (ACC) with the magnitude of inhibition different in the two lines. In contrast, ICV injection of 4 nmol obestatin did not affect mRNA expression of AMPK system or phosphorylation of AMPK and ACC in either line. These data support the premise of a lower threshold for anorexigenic effect of central ghrelin in LWS than HWS chicks, and this difference may be associated with differential hypothalamic AMPK signaling. Additionally, the hypothalamic mRNA level of ghrelin was significantly higher in LWS than HWS, which may have also contributed to the different threshold response to ghrelin in these two lines. The expression of the ghrelin receptor was also higher in the LWS line, but not until 56 days of age. In summary, selection for body weight has resulted in differences in the central ghrelin and obestatin system, and an altered brain AMPK system may contribute to the different neuronal response to ghrelin, but not obestatin.

Chronic L-tyrosine alters the locomotor activity and brain monoamine levels in Roborovskii hamsters.

The Roborovskii hamster (Phodopus roborovskii) has high locomotor activity (hyperactivity) and low dopamine levels in the brain compared with the congeneric Djungarian hamster (Phodopus sungorus). To clarify the efficacy of dietary l-tyrosine in ameliorating signs of hyperactivity, we investigated the effects of chronic administration of l-tyrosine, the primary precursor of dopamine, on locomotor activity and brain monoamine levels in Roborovskii hamsters. Chronic supplementation of l-tyrosine had no effect on locomotor activity in the open field, but did decrease locomotor activity in the home cage. Tyrosine increased dopamine and norepinephrine turnover rates and decreased in serotonin turnover rate in the brain. These findings suggest that long-term feeding of l-tyrosine may be effective in ameliorating signs of hyperactivity.

Central L-ornithine, but not polyamines, induces a hypnotic effect in neonatal chicks under acute stress.

To clarify whether L-ornithine and/or its metabolite involves sedative and hypnotic effects under social separation stress, the effects of intracerebroventricular (i.c.v.) injection of L-ornithine and polyamines (putrescine, spermidine and spermine) were compared in chicks. Birds were injected i.c.v. with 0.5 mumol of L-ornithine, putrescine, spermidine, spermine or saline (control). After injection, chicks were immediately separated from the flock and monitored for the number of distress vocalizations and various postures. L-Ornithine greatly attenuated the stress response and caused sedative and hypnotic effects. Among the polyamines, only putrescine attenuated distress vocalizations but did not induce sleep. In conclusion, the sedative and hypnotic effect of L-ornithine was mainly induced by L-ornithine itself, while the polyamines contributed to the sedative, but not hypnotic, effect under social separation stress.

Norepinephrine does not alter NPY and POMC mRNA expression in neonatal chicks.

Norepinephrine (NE), synthesized in both the central and peripheral nervous system, is involved in food intake regulation of both mammals and chickens. Neuropeptide Y (NPY), a potent orexigenic peptide, is colocalized with NE neurons in the central and peripheral nervous system, suggesting an interaction. Proopiomelanocortin (POMC) is the precursor of alpha-melanocyte stimulating hormone, a potent anorexigenic peptide synthesized in the hypothalamus. In this study, two experiments were conducted to examine the effect of intracerebroventricular (ICV) injection of NE on appetite mediators in neonatal chicks (Gallus gallus). Experiment 1 was done to confirm the effect of centrally administered NE (0, 25, 50, and 100 microg) on food intake following a 3h fast, and to determine the change in NPY mRNA expression in the central nervous system (CNS). In Experiment 2, chicks fed ad libitum were treated ICV with NE (50 microg) to determine if changes occurred in brain NPY and POMC mRNA levels. In Experiment 1, the ICV injection of NE dose-dependently reduced food intake, but there was no change in NPY mRNA expression in the CNS. In Experiment 2, there was no significant change in NPY and POMC mRNA expression between the control and NE-treated group, indicating that ICV injection of NE may not be associated with changes in NPY or POMC gene expression.

Oral administration of L-serine reduces the locomotor activity of socially isolated rats.

L-Serine is considered a functional amino acid in the central nervous system, since intracerebroventricular injection of L-serine induced sedative and hypnotic effects in neonatal chicks exposed to acute stressful conditions. Accordingly, L-serine is a candidate anti-stress factor, but the effect of daily intake of L-serine on behavior of animals exposed to chronic stress has not been investigated. In the present study, we exposed rats to social isolation stress for 4 weeks, and home cage test and open field test were concluded to evaluate the effect of L-serine on behavior. To investigate L-serine supplementation modifies the brain L-serine and its metabolite contents, free amino acid contents were measured by a high performance liquid chromatography. L-Serine in the drinking water increased L-serine levels in some brain areas, but changes in its metabolites were almost negligible. L-Serine decreased locomotor activity in rats exposed to a familiar environment. In addition, L-serine decreased exploratory behavior of isolated rats, even in a novel environment. Our results could suggest that daily intake of L-serine can attenuate symptoms induced by chronic stress.

Oral administration of Excitin-1 (beta-alanyl-L-leucine) alters behavior and brain monoamine and amino acid concentrations in rats.

We previously demonstrated that beta-alanyl-branched chain amino acids have excitatory effects. Therefore, we named beta-alanyl-L-leucine, beta-alanyl-L-isoleucine and beta-alanyl-L-valine as Excitin-1, -2, and -3 , respectively. Since there is little known about the effects of Excitins, we clarified whether oral administration of Excitin-1 affects behavior in rats, alters the monoamine and amino acid levels in the central nervous system, whether Excitin-1 is incorporated into the brain, and how long it remains in the blood. Excitin-1 increased motor behavior, increasing the distance of path and number of rearings in the open field. Excitin-1 influenced some monoamine and amino acid levels in the cerebral cortex and hypothalamus. Following oral administration, Excitin-1 was detected in the cerebral cortex, hypothalamus, hippocampus and olfactory bulb. In the plasma, Excitin-1 and its metabolites beta-alanine and L-leucine were recorded. The present study demonstrated that Excitin-1 was incorporated in the brain and promoted behavioral changes in rats.

Central l-proline attenuates stress-induced dopamine and serotonin metabolism in the chick forebrain.

Using microdialysis, we investigated the effect of l-proline on monoamine release in the medio-rostral neostriatum/hyperstriatum ventrale (MNH) of freely moving and restricted chicks. A 30 min handling-stress resulted in a significant increase in extracellular homovallinic acid (HVA), a dopamine metabolite, and 5-hydroxyindoleacetic acid (5-HIAA), a serotonin metabolite, in the MNH. l-Proline, perfused through the microdialysis probe into the MNH during the stressed condition, significantly attenuated the average dialysate concentration of HVA produced by handling-stress. Handling-stress resulted in a significant increase in 5-HIAA levels in the control group, which were attenuated by profusion with l-proline. l-Proline did not significantly modify basal concentrations of HVA or 5-HIAA in the MNH during control conditions. These results show that perfusion of l-proline modified the turnover/metabolism of dopamine and serotonin in the MNH caused by handling-stress.