Xiaochaihutang prevents depressive-like behaviour in rodents by enhancing the serotonergic system.

OBJECTIVES: Xiaochaihutang (XCHT) has been used in China for thousands of years to treat 'Shaoyang syndrome', which involves depressive-like symptoms. However, no studies were conducted to demonstrate its antidepressant effect and mechanism. This study was designed to confirm the antidepressant effect of XCHT and explore its mechanism using the pharmacological methods. METHODS: Ultra-HPLC and mass spectrometry was used to identify the chemical constituents of XCHT. Forced swimming test (FST) and tail suspension test (TST) were used to determine the antidepressant-like activity of XCHT in mice and rats. The possible mechanism of XCHT was elucidated by the reserpine-induced hypothermia and 5-hydroxytryptophan (5-HTP)-induced head-twitch in mice. The levels of serotonin (5-HT) and 5-hydroxyindoleacetic acid (5-HIAA) were measured in prefrontal cortex and hippocampus tissue of both mice and rats. Moreover, the extracellular 5-HT in rat hippocampus was assessed by using microdialysis coupled to HPLC with electrochemical detection. KEY FINDINGS: Forty-four components were detected in XCHT. XCHT significantly reduced immobility time in the TST and the FST, antagonized reserpine-induced depressive-like behaviours, increased 5-HTP-induced head-twitches, elevated 5-HT and 5-HIAA levels, and increased 5-HT turnover at doses that did not affect general activity. CONCLUSIONS: These data demonstrate that XCHT has therapeutic effects in animal models of depression by enhancing the serotoninergic system in the prefrontal cortex and hippocampus.

Neuronal metabolomics by ion mobility mass spectrometry: cocaine effects on glucose and selected biogenic amine metabolites in the frontal cortex, striatum, and thalamus of the rat.

We report results of studies of global and targeted neuronal metabolomes by ambient pressure ion mobility mass spectrometry. The rat frontal cortex, striatum, and thalamus were sampled from control nontreated rats and those treated with acute cocaine or pargyline. Quantitative evaluations were made by standard additions or isotopic dilution. The mass detection limit was ~100 pmol varying with the analyte. Targeted metabolites of dopamine, serotonin, and glucose followed the rank order of distribution expected between the anatomical areas. Data was evaluated by principal component analysis on 764 common metabolites (identified by m/z and reduced mobility). Differences between anatomical areas and treatment groups were observed for 53 % of these metabolites using principal component analysis. Global and targeted metabolic differences were observed between the three anatomical areas with contralateral differences between some areas. Following drug treatments, global and targeted metabolomes were found to shift relative to controls and still maintained anatomical differences. Pargyline reduced 3,4-dihydroxyphenylacetic acid below detection limits, and 5-HIAA varied between anatomical regions. Notable findings were: (1) global metabolomes were different between anatomical areas and were altered by acute cocaine providing a broad but targeted window of discovery for metabolic changes produced by drugs of abuse; (2) quantitative analysis was demonstrated using isotope dilution and standard addition; (3) cocaine changed glucose and biogenic amine metabolism in the anatomical areas tested; and (4) the largest effect of cocaine was on the glycolysis metabolome in the thalamus confirming inferences from previous positron emission tomography studies using 2-deoxyglucose.

Ginkgo biloba leaf extract (EGb 761®) and its specific acylated flavonol constituents increase dopamine and acetylcholine levels in the rat medial prefrontal cortex: possible implications for the cognitive enhancing properties of EGb 761®.

Experimental and clinical data suggest that the Ginkgo biloba standardized extract EGb 761® exerts beneficial effects in conditions which are associated with impaired cognitive function. However, the neurochemical correlates of these memory enhancing effects are not yet fully clarified. The aim of this study was to examine the effect of repeated oral administration of EGb 761® and some of its characteristic constituents on extracellular levels of dopamine (DA), noradrenaline (NA), serotonin (5-HT), acetylcholine (ACh) and the metabolites 3,4-dihydroxyphenylacetic acid (DOPAC), homovanillic acid (HVA) and 5-hydroxyindoleacetic acid (5-HIAA) in the medial prefrontal cortex (mPFC) of awake rats by use of in vivo microdialysis technique. Subacute (14 days, once daily), but not acute, oral treatment with EGb 761® (100 and 300 mg/kg) or the flavonoid fraction, which represents about 24% of the whole extract caused a significant and dose-dependent increase in extracellular DA levels in the mPFC. Repeated administration of EGb 761® also caused a modest but significant increase in the NA levels, whereas the concentrations of 5-HT and those of the metabolites DOPAC, HVA and 5-HIAA were not affected. The same treatment regimen was used in a subsequent study with the aim of investigating the effects of two Ginkgo-specific acylated flavonols, 3-O-(2''-O-(6'''-O-(p-hydroxy-trans-cinnamoyl)-ß-D-glucosyl)-α-L-rhamnosyl)quercetin (Q-ag) and 3-O-(2''-O-(6'''-O-(p-hydroxy-trans-cinnamoyl)-ß-D-glucosyl)-α-L-rhamnosyl)kaempferol (K-ag). Both compounds together represent about 4.5% of the whole extract. Repeated oral treatment with Q-ag (10 mg/kg) for 14 days caused a significant increase in extracellular DA levels of 159% and extracellular acetylcholine (ACh) levels of 151% compared to controls. Similarly, administration of K-ag (10 mg/kg) induced a significant rise of DA levels to 142% and ACh levels to 165% of controls, whereas treatment with isorhamnetin, an O-methylated aglycon component of EGb 761® flavonol glycosides had no effect. None of the tested flavonoids had a significant effect on extracellular DOPAC and HVA levels. The present findings provide evidence that the subacute treatment with EGb 761® and its flavonol constituents increases DA and ACh release in the rat mPFC, and suggest that the two Ginkgo-specific acylated flavonol glycosides Q-ag and K-ag are active constituents contributing to these effects. As seen for isorhamnetin, the effect on neurotransmitter levels seems not to be a general effect of flavonols but rather to be a specific action of acylated flavonol glycosides which are present in EGb 761®. The direct involvement of these two flavonol derivatives in the increase of dopaminergic and cholinergic neurotransmission in the prefrontal cortex may be one of the underlying mechanisms behind the reported effects of EGb 761® on the improvement of cognitive function.

Estrous cycle affects the neurochemical and neurobehavioral profile of carvacrol-treated female rats.

Carvacrol is the major constituent of essential oils from aromatic plants. It showed antimicrobial, anticancer and antioxidant properties. Although it was approved for food use and included in the chemical flavorings list, no indication on its safety has been estimated. Since the use of plant extracts is relatively high among women, aim of this study was to evaluate carvacrol effects on female physiology and endocrine profiles by using female rats in proestrus and diestrus phases. Serotonin and metabolite tissue content in prefrontal cortex and nucleus accumbens, after carvacrol administration (0.15 and 0.45g/kg p.o.), was measured. Drug effects in behavioral tests for alterations in motor activity, depression, anxiety-related behaviors and endocrine alterations were also investigated. While in proestrus carvacrol reduced serotonin and metabolite levels in both brain areas, no effects were observed in diestrus phase. Only in proestrus phase, carvacrol induced a depressive-like behavior in forced swimming test, without accompanying changes in ambulation. The improvement of performance in FST after subchronic treatment with fluoxetine (20mg/kg) suggested a specific involvement of serotonergic system. No differences were found across the groups with regard to self-grooming behavior. Moreover, in proestrus phase, carvacrol reduced only estradiol levels without binding hypothalamic estradiol receptors. Our study showed an estrous-stage specific effect of carvacrol on depressive behaviors and endocrine parameters, involving serotonergic system. Given the wide carvacrol use not only as feed additive, but also as cosmetic essence and herbal remedy, our results suggest that an accurate investigation on the effects of its chronic exposure is warranted.

Central fatigue induced by losartan involves brain serotonin and dopamine content.

PURPOSE: To investigate the influence of angiotensin II (Ang II) AT1 receptors blockade on central fatigue induced by brain content of serotonin (5-HT) and dopamine (DA) during exercise. METHODS: Losartan (Los) was intracerebroventricularly injected in rats before running until fatigue (n = 6 per group). At fatigue, brains were quickly removed for measurement of 5-HT, 5-hydroxyindoleacetic acid (5-HIAA), DA, and 3,4-dihydroxyphenylacetic acid by high-pressure liquid chromatography in the preoptic area, hypothalamus, hippocampus, and frontal cortex. RESULTS: Intracerebroventricular injection of Los increased 5-HT content in the preoptic area and hypothalamus. Such results correlated positively with body heating rate and inversely with time to fatigue. On the other hand, time to fatigue was directly correlated with the diminished concentration of 5-HT in the hippocampus of Los rats. Although the levels of DA were not affected by Los treatment during exercise in any of the brain areas studied, a higher 5-HT/DA ratio was seen in the hypothalamus of Los animals. This higher hypothalamic 5-HT/DA ratio correlated positively with body heating rate and negatively with time to fatigue. CONCLUSIONS: Our results show that central fatigue due to hyperthermia and increased body heating rate induced by central Ang II AT1 receptor blockade in exercising rats is related with higher 5-HT content in the preoptic area and hypothalamus as well as with decreased levels of this neurotransmitter in the hippocampus. Furthermore, the interaction between 5-HT and DA within the hypothalamus seems to contribute to hyperthermia and premature central fatigue after angiotensinergic inhibition.

Influence of intracerebroventricular or intraperitoneal administration of cannabinoid receptor agonist (WIN 55,212-2) and inverse agonist (AM 251) on the regulation of food intake and hypothalamic serotonin levels.

The effect of intracerebroventricular or intraperitoneal administration of cannabinoid receptor agonist WIN 55,212-2 or inverse agonist AM 251 on food intake and extracellular levels of serotonin and acetic acid 5-hydroxy-indol from presatiated rats was studied. Compared to the vehicle-injected control, the intracerebroventricular administration of WIN 55,212-2 was associated with a significant increase in food intake, whereas the administration of AM 251 caused a significant reduction in this respect. These results were accompanied by considerable reductions or increases in serotonin and acetic acid 5-hydroxy-indol levels compared to the vehicle-injected control and the baseline values for the different experimental groups studied. Intraperitoneal administration of WIN 55,212-2 at doses of 1 and 2 mg/kg promoted hyperphagia up to 6 h after injection, whereas administration of a higher dose (5 mg/kg) significantly inhibited food intake and motor behaviour in partially satiated rats. Administration of any of the AM 251 doses studied (0.5, 1, 2, 5 mg/kg) led to a significant decrease in the amount of food ingested from 2 h after the injection, compared to the vehicle-injected control group, with the most striking effect being observed when the 5 mg/kg dose was injected.

Exaggerated feedback control decreases brain serotonin concentration and elicits hyperactivity in a rat model of diet-restriction-induced anorexia nervosa.

5-Hydroxytryptamine (5-HT; serotonin) system is the major neurotransmitter system of interest in research on anorexia nervosa (AN). The AN patients show extreme dieting weight loss, hyperactivity and low basal levels of 5-hydroxyindoleacetic acid (5-HIAA), a major metabolite of 5-HT in the cerebrospinal fluid (CSF). Studies on animal models show that diet restriction (DR) decreases 5-HT metabolism in the brain and hypothalamus which is not necessarily associated with a decrease in the availability of essential amino acid tryptophan (TRP) the precursor of serotonin. To further investigate the mechanism involved in DR-induced decreases of 5-HT the present study uses 8-hydroxy-(2-di-n-propylamino) tetralin (8-OH-DPAT), a selective 5-HT-1A agonist, as a probe to monitor the responsiveness of negative feedback control over 5-HT metabolism. Effects of DR and of 8-OHDPAT on TRP, 5-HT and 5-HIAA concentrations are determined in the hypothalamus, a region of the brain known to role in the regulation of appetite. Animals of DR group given access to food 2h daily for 6 days exhibited 21.6% decrease in the body weight compared to freely feeding (FF) controls. The levels of TRP in the plasma and of 5-HT in the hypothalamus decreased. No effect was found on the levels of TRP in the hypothalamus. 8-OH-DPAT-induced decreases of 5-HT and 5-HIAA were greater in DR than FF group. 8-OH-DPAT-induced hyperactivity was also greater in DR than FF group. The results show that DR-induced decreases of 5-HT are due to an increase in the responsiveness of negative feedback control over 5-HT and not due to smaller availability of TRP. DR-induced increase in activity and 8-OH-DPAT-induced greater hyperactivity in DR than FF group may also be due to exaggerated negative feedback control over 5-HT. It is suggested that drugs decreasing the responsiveness of negative feedback control over 5-HT may be of use for the treatment and prevention of AN in under weight patients on restricted diet.

Effect of acute tryptophan depletion on noradrenaline and dopamine in the rat brain.

In human subjects, the acute tryptophan (TRP) depletion (ATD) paradigm has been shown to have effects on mood and cognition. It is assumed that these effects are mediated through the serotonin system. In this study, we have examined the effects of ATD on the central concentrations of the monoamine transmitters, noradrenaline (NA) and dopamine (DA) as well as on serotonin (5-HT). Effects on NA and DA could also affect mood and cognition. Following oral administration of TRP-containing (TRP+) and TRP-free (TRP-) amino acid mixtures, neurotransmitter concentrations and free plasma TRP concentrations were determined by High Performance Liquid Chromatography (HPLC) with electrochemical detection. Free plasma TRP was significantly and substantially reduced (79%) in rats given a TRP- amino acid mixture when compared with those given a TRP+ mixture. ATD also significantly decreased 5-HT and 5-hydroxyindolacetic acid in the frontal cortex, remaining cortex and hippocampus, but did not significantly reduce these in the striatum. Furthermore, ATD did not significantly alter the concentration of NA and DA in any brain region examined. This study demonstrates that the administration of a TRP- amino acid mixture in rats can reduce free plasma TRP to levels comparable to those reported in human studies. These results indicate that behavioural and cognitive changes produced by ATD in preclinical or clinical studies are likely to be due to specific effects on the serotonergic system.

Long-term consumption of sugar-rich diet decreases the effectiveness of somatodendritic serotonin-1A receptors.

8-Hydroxy-2-(di-n-propylamino)-tetralin (8-OH-DPAT), a 5-hydroxytryptamine (5-HT)-1A selective agonist was used to investigate a possible role of somatodendritic serotonin-1A receptors in the precipitation of hyperphagia and decreases of 5-HT metabolism associated with long-term consumption of sugar rich-diet. In the first part of study, dose-related hyperphagic effects of 8-OH-DPAT were monitored in freely feeding rats. In the second part of study, rats were fed freely on a sugar-rich diet (prepared by mixing standard rodent diet with table sugar in the ratio of 3:1 [w/w]) for 5 weeks. Hyperphagic effects of 8-OH-DPAT were monitored in sugar-rich diet and normal diet treated rats by injecting the drug at a dose of 0.25 mg/kg body weight, a dose that produced significant hyperphagia. Effects of 8-OH-DPAT on decreasing 5-HT metabolism in the hypothalamus were also investigated in the two groups. Results showed that administration of 8-OH-DPAT at a dose of 0.25 mg/kg body weight elicited hyperphagia and decreased 5-HT metabolism in normal diet treated animals but the effects in sugar-rich diet treated animals were smaller and not significant suggesting a decrease in the effectiveness of somatodendritic 5-HT-1A receptors, which provide a feedback control over the synthesis and release of 5-HT in terminal region. A possible mechanism involved in sugar-diet induced decreases of 5-HT metabolism is discussed.

Capillary electrophoretic separation of biologically active amines and acids using nanoparticle-coated capillaries.

This manuscript describes dynamic coating of capillaries with poly(L-lysine) (PLL) and silica nanoparticles (SiO2 NPs) and use of the as-prepared capillaries for the separation of biogenic amines and acids by CE in conjunction with LIF detection. The directions of EOF are controlled by varying the outmost layer of the capillaries with PLL and SiO2 NPs, respectively. Over the pH range 3.0-5.0, the (PLL-SiO2NP)n-PLL capillaries have an EOF toward the anodic end and are more suitable for the separation of acids with respect to speed, while the (PLL-SiO2NP)n capillaries have an EOF toward the cathodic end and are more suitable for the separation of biogenic amines regarding speed and sensitivity. The separations of standard solutions containing five amines and two acids by CE with LIF detection using (PLL-SiO2NP)2-PLL and (PLL-SiO2NP)3 capillaries were accomplished within 10 and 7 min, providing plate numbers of 3.8 and 5.0x10(4) plates/m for 5-hydroxytryptamine (5-HT), respectively. The LODs for 5-HT and 5-hydroxyindole-3-acetic acid (5-HIAA) are 32 and 2 nM and 0.2 and 1.5 nM when using the (PLL-SiO2NP)2-PLL and (PLL-SiO2NP)3 capillaries, respectively. Identification and quantification of 5-HIAA, homovanillic acid, and DL-vanillomandelic acid in urine samples from a male before and after drinking green tea were tested to validate practicality of the present approach. The results show that the (PLL-SiO2NP)2-PLL capillary provides greater resolving power, while the (PLL-SiO2NP)3 capillary provides better sensitivity, higher efficiency, and longer durability for the separation of the amines and acids.

Dexamethasone reduces food intake, weight gain and the hypothalamic 5-HT concentration and increases plasma leptin in rats.

This study was conducted to define the regulatory mechanisms underlying stress-induced decreases in food intake and weight gain. Rats received a single or 4 daily injections of dexamethasone (0.1 or 1 mg/kg). Food intake and weight gain were recorded, and plasma leptin, brain contents of serotonin (5-hydroxytryptamine; 5-HT), 5-hydroxy-indole-acetic acid (5-HIAA) and the raphe expression of tryptophan hydroxylase (TPH), monoamine oxidase A (MAO-A) and 5-HT reuptake transporter (5-HTT) genes were examined. A single injection of dexamethasone did not acutely affect food intake, but cumulative food intake and weight gain were suppressed dose-dependently by daily injections of dexamethasone. Both a single and repeated injections of dexamethasone elevated plasma leptin in a dose dependent manner. 5-HT contents in the hypothalamus was decreased, but 5-HIAA increased, both by a single and repeated dexamethasone. A single injection of dexamethasone did not affect mRNA expressions of TPH, MAO-A and 5-HTT genes, but repeated dexamethasone increased them in the dorsal raphe nucleus. These results suggest that plasma leptin may play a role in dexamethasone-induced anorexia. Additionally, increased expression of MAO-A and 5-HTT genes by repeated dexamethasone appears to be implicated in decreases of the brain 5-HT contents.

Serotoninergic system blockage in the prepubertal rat inhibits spermatogenesis development.

The stimulatory and inhibitory role of serotonin in gonadotropin secretion and in the onset of puberty in the male rat has been previously described, but its role in the establishment of spermatogenesis is not known. The aim of this study was to investigate the effects of serotoninergic inhibition by p-chloroamphetamine (pCA) on the prepubertal-to-adult stage of the rat reproductive system. Hypothalamic serotonin, gonadotropins and sex steroid hormone concentrations were measured, and a histopathological analysis of seminiferous epithelium was carried out on animals treated with pCA from day 30 and killed at 45 or 65 days of age. The pCA treatment significantly reduced the hypothalamic levels of serotonin and its metabolite (5-hydroxyindole-3-acetic acid). This inhibition did not affect the sex steroid hormone or LH concentrations, but rather it induced an increase in FSH concentration in animals of both ages. Spermatogenesis was impaired by pCA treatment. Disruption of seminiferous epithelium and the death of numerous germ cells were observed. Sperm produced by pCA-treated animals was of poor quality and appeared in small quantities. Apparently, serotonin depletion did not affect communication between the hypothalamus and the pituitary, but the FSH increase could have been related to alterations in the seminiferous epithelium effects. The seminiferous epithelium cycle was altered in rats killed at both 45 and 65 days of age, because at each age of killing the distribution of spermatogenesis stages was different. Germ cell apoptosis did not appear to be related to changes in the FSH concentrations, but other factors produced during spermatogenesis could have been involved in this induction. This study showed that serotonin was necessary for the development of normal spermatogenesis in prepubertal rats.

Caloric intake and hypothalamic neurotransmitters in Zucker rats made acutely diabetic with streptozocin.

Zucker rats, lean and obese, treated with low dose intraperitoneal injections of streptozocin become hyperglycemic within 24h. Insulin levels fall, although the obese animal remains hyperinsulinemic. Associated with these changes in glucose and insulin there are transient decreases in caloric intake. Macronutrient selection studies show that protein consumption decreases. There is a trend for fat intake to decrease. The levels of hypothalamic neurotransmitters in the lean animals are not altered by streptozocin. The levels of 5-hydroxyindoleacetic acid increases in the streptozocin-treated obese animal in the paraventricular region, ventromedial region and the raphe. Serotonin is also significantly increased in the paraventricular region of the obese rat. These results suggest that acutely, treatment with streptozocin injures pancreatic islets, causing, in turn, decreases in insulin levels so that hyperglycemia ensues in both phenotypes. Associated with these perturbations are decreases in caloric intake. The magnitude of change in insulin levels is much greater in the obese rat. It is hypothesized that in the obese Zucker rat decrements in food intake are mediated by increase in serotonin turnover in the hypothalamus and these changes are related to changes of insulin levels. These data support the concept that circulating insulin affects hypothalamic neurotransmitters.

Stimulatory effect of oral administration of green tea and caffeine on locomotor activity in SKH-1 mice.

Administration of green tea or caffeine was shown previously to inhibit ultraviolet B light-induced carcinogenesis in SKH-1 mice, and this effect was associated with a reduction in dermal fat. In the present study, oral administration of 0.6% green tea (6 mg tea solids/ml) or 0.04% caffeine (0.4 mg/ml; equivalent to the amount of caffeine in 0.6% green tea) as the sole source of drinking fluid to SKH-1 mice for 15 weeks increased total 24 hr locomotor activity by 47 and 24%, respectively (p<0.0001). Oral administration of 0.6% decaffeinated green tea (6 mg tea solids/ml) for 15 weeks increased locomotor activity by 9% (p<0.05). The small increase in locomotor activity observed in mice treated with decaffeinated green tea may have resulted from the small amounts of caffeine still remaining in decaffeinated green tea solutions (0.047 mg/ml). The stimulatory effects of orally administered green tea and caffeine on locomotor activity were paralleled by a 38 and 23% increase, respectively, in the dermal muscle layer thickness. In addition, treatment of the mice with 0.6% green tea or 0.04% caffeine for 15 weeks decreased the weight of the parametrial fat pad by 29 and 43%, respectively, and the thickness of the dermal fat layer was decreased by 51 and 47%, respectively. These results indicate that oral administration of green tea or caffeine to SKH-1 mice increases locomotor activity and muscle mass and decreases fat stores. The stimulatory effect of green tea and caffeine administration on locomotor activity described here may contribute to the effects of green tea and caffeine to decrease fat stores and to inhibit carcinogenesis induced by UVB in SKH-1 mice.

The effects of phenylpropanolamine on Zucker rats selected for fat food preference.

Treatments of human and rodent obesity frequently involve administration of amphetamine derivatives, much like phenylpropanolamine, which suppress food intake. The Zucker rat is a commonly employed model of youth-onset obesity in which the homozygous genotype manifests hyperphagia as well as other characteristics that parallel human obesity. Using a macronutrient selection procedure, we examined phenylpropanolamine's differential actions in controlling dietary intake, spontaneous open-field activity, and regional hypothalamic neurotransmitter levels in obese female Zucker rats of varying fat food preference. We hypothesized that phenylpropanolamine would alter hypothalamic monoamine levels differently in low-fat preferring and high-fat preferring Zucker rats, and hence affect feeding behavior and activity differently in these two groups. It was found that in high-fat preferring animals, phenylpropanolamine significantly decreased spontaneous open-field activity, decreased only carbohydrate caloric intake, and increased serotonin and 5-HIAA levels in the paraventricular nucleus (PVN). In low-fat preferring animals, phenylpropanolamine decreased carbohydrate, protein, and total caloric intake, had no significant effect of spontaneous activity, and increased serotonin and 5-hydroxyindole acetic acid levels in the PVN. Inherent and induced physiological differences of low-fat and high-fat preferring animals are discussed as well as phenylpropanolamine's potential in combination drug therapy for the treatment of human hyperphagic obesity.

Influence of time of day on hypothalamic monoaminergic activity in early pregnancy: effect of a previous reproductive experience.

Several dopamine-related neurochemical and behavioral responses are influenced by the time of day. The light-dark shift is a major zeitgeber for various functionally important hypothalamic monoaminergic systems. However, these influences are modulated by reproductive state and by reproductive experience (RE) in females. Early pregnancy in rodents generates diurnal and nocturnal prolactin surges that are reduced in intensity in a second pregnancy. Dopamine (DA) is a major inhibitory factor of prolactin synthesis and secretion. Other neurotransmitters such as serotonin (5HT) and norepinephrine (NE) can modulate prolactin secretion as well. Previous works have demonstrated that RE induces changes in central concentrations of both dopamine and serotonin. In addition, RE modulates the responses of both dopaminergic and serotoninergic nerve terminals. The present investigation was designed to examine the possible effects of RE on hypothalamic concentrations of DA, NE, 5HT and their major metabolites homovanillic acid (HVA), 3-4-dihydroxyphenyl acetic acid (DOPAC), 3-methoxy mandelic acid (VMA) and 5-hydroxyindole 3-acetic acid (5HIAA), respectively. These parameters were measured in pregnant rats during the light-dark shift and the prolactin surges. Primi- and multigravid rats were sacrificed on the 7th-8th day of pregnancy between 1700 and 1900 h (light-dark shift and diurnal prolactin surge) or 0200 and 0400 h (nocturnal prolactin surge), and hypothalamic concentrations of DA, NE and 5HT and their metabolites were measured by high performance liquid chromatography coupled to an electrochemical detector (HPLC-ED). Trunk blood was collected and serum prolactin measured by radioimmunoassay. The prolactin surge was confirmed and multigravid rats showed significantly lower serum prolactin levels as compared to primigravid rats between 0200 and 0400 h. During the light-dark shift DA and NE concentrations increased while DOPAC/DA, HVA/DA and 5HIAA/5HT ratios decreased in multigravid rats compared to primigravid rats. Except for 5HIAA/5HT, these differences were not observed during the prolactin nocturnal surge. These results suggest that a previous reproductive experience induces central functional changes during pregnancy which are expressed differently according to the time of day.

Nandrolone decanoate enhances hypothalamic biogenic amines in rats.

PURPOSE: To identify possible mechanisms for an anabolic-androgenic steroid induced increase in aggressive behavior and work capacity, the levels of some biogenic amines considered to be closely related to a systemic hyper-adrenergic state were measured in selected regions of the brain. METHODS: Wistar male rats were divided randomly into five groups: nontreated (control), oil-vehicle-treated (vehicle) or one of three (therapeutic dose and 10- or 100-fold higher dose) anabolic-androgenic steroid-treated (steroid-1, -2, -3) groups. Rats in the steroid and vehicle groups were given a single dose of nandrolone decanoate or oil vehicle, respectively, one week before tissue sampling. The levels of norepinephrine (NE) and its metabolite, 4-hydroxy-3-methoxyphenylglycol (MHPG), serotonin (5-HT) and its metabolite, 5-hydroxy-indole-3-acetic acid (5-HIAA) were measured in the cerebral cortex, hypothalamus and cerebellum by high-performance liquid chromatography. Immunostaining for c-fos was performed as a confirmation of increased neural activity. RESULTS: The levels of NE and MHPG were increased by approximately 2- and approximately 7-fold in the hypothalamus of the steroid-2 compared with the control and vehicle groups. The levels of 5-HT and 5-HIAA were approximately 40 and approximately 50% higher in the steroid-2 compared with the control and vehicle groups. A significantly higher number of c-fos expressing neurons were observed in the periventricular region of the steroid-2 than the control and vehicle groups, indicating enhanced neuronal activity after nandrolone decanoate treatment. CONCLUSIONS: The present results, combined with previously reported findings of physical performance enhancement after anabolic-androgenic steroid treatment, are consistent with the interpretation that elevated levels of adrenergic and serotonergic amines in the hypothalamus could contribute to aggressive behaviors as well as improved physical performance.

Hypothalamic indolamines during embryonic development and effects of steroid exposure.

The serotonin system has been implicated in the modulation of endocrine and behavioral components of reproduction. In this study, we examined endogenous hypothalamic indolamines during sexual differentiation and long-term effects of exogenous steroids during this time. In Experiment 1, Japanese quail were studied during the last half of embryonic development and early post-hatch. Samples were taken at embryonic day 10 (E10), E12, E14, E16, hatch (day 0), and days 3 and 5, post-hatch. Hypothalamic indolamines, including serotonin (5-HT) and its metabolite, 5-hydroxy indole acetic acid (5-HIAA) were measured by HPLC-EC detection. Females had relatively higher hypothalamic 5-HT at E14 than males, with both sexes showing increasing levels thereafter. By day 5, post-hatch, hypothalamic 5-HT content was higher in males than in females. When turnover was estimated by comparing relative concentrations of 5-HT to 5-HIAA, males were significantly higher at E12 and E14 than females. These data suggest that there are stage specific changes in the serotonin system, as well as sexually dimorphic patterns in the ontogeny and activity of this system. In Experiment 2, we investigated the effects of embryonic steroid hormone treatment on the serotonin system and on male sexual behavior. Birds were treated with either estradiol benzoate (EB), testosterone propionate (TP) or sesame oil (vehicle control) at selected embryonic days (E10, E12, E14, E16, 0, D3, and D5). At 4 weeks post-hatch, birds were transferred to short photoperiod (16D:8L) for 3 weeks to prevent photostimulated reproductive development. At 7 weeks of age, males were implanted with a 20mm silastic capsule filled with testosterone and sexual behavior was tested 1 week later. Brains were collected from both males and females, and preoptic area (POA) indolamines were measured. Steroid treatment at E10 or E12 resulted in the loss of male sexual behavior. Moreover, males treated with EB or TP on E12 also had increased POA 5-HT content as adults, compared to control males. Females treated with EB on either E10 or E 12 also had higher POA 5-HT content than control or TP treated females. These data provide evidence for sexual dimorphism in the hypothalamic 5-HT system at specific stages during embryonic development. Moreover, males were sensitive to exogenous EB and TP on E12, whereas females appeared to be affected by EB only and appeared to be sensitive to steroid effects over a longer period of time in development. Moreover, exogenous steroids at E12 in males also correlated with impaired sexual behavioral. These data suggest that long-term effects of embryonic steroid exposure may be mediated in part through effects on the serotonin neurotransmitter system.

Elevated dietary intake of L-tryptophan counteracts the stress-induced elevation of plasma cortisol in rainbow trout (Oncorhynchus mykiss).

Juvenile rainbow trout were isolated in individual compartments and allowed to acclimate for 1 week, during which they were fed commercial trout pellets. The feed was then replaced by pelleted feed supplemented with L-tryptophan (TRP) at two, four or eight times the concentration in the commercial feed. Fish were fed these supplemented feeds daily to satiety for 1 week, after which half of the fish were stressed, by lowering the water level for 2 h, while the remaining fish were left undisturbed. In undisturbed fish, supplementary dietary TRP resulted in slightly elevated plasma cortisol levels. In response to the stress, fish that had been fed control feed showed elevated plasma cortisol levels, but fish fed the TRP-supplemented feed displayed a significant reduction in this stress-induced elevation of plasma cortisol levels. Plasma and brain TRP levels were elevated in fish fed TRP-supplemented feed. TRP is the precursor of the monoamine neurotransmitter serotonin. Brain serotonergic activity was elevated by stress and also tended to be increased by elevated dietary TRP intake. The central serotonergic system is involved in the control of the hypothalamic-pituitary-interrenal axis, the action of serotonin being to stimulate or inhibit this neuroendocrine axis through different projections.

Decreased brain histamine content in hypocretin/orexin receptor-2 mutated narcoleptic dogs.

A growing amount of evidence suggests that a deficiency in hypocretin/orexin neurotransmission is critically involved in animal and human forms of narcolepsy. Since hypocretin-containing neurons innervate and excite histaminergic tuberomammillary neurons, altered histaminergic neurotransmission may also be involved in narcolepsy. We found a significant decrease in histamine content in the cortex and thalamus, two structures important for histamine-mediated cortical arousal, in Hcrtr-2 mutated narcoleptic Dobermans. In contrast, dopamine and norepinephrine contents in these structures were elevated in narcoleptic animals, a finding consistent with our hypothesis of altered catecholaminergic transmission in these animals. Considering the fact that histamine promotes wakefulness, decreases in histaminergic neurotransmission may also account for the sleep abnormalities in hypocretin-deficient narcolepsy.