The High-Precision Liquid Chromatography with Electrochemical Detection (HPLC-ECD) for Monoamines Neurotransmitters and Their Metabolites: A Review.

This review highlights the advantages of high-precision liquid chromatography with an electrochemical detector (HPLC-ECD) in detecting and quantifying biological samples obtained through intracerebral microdialysis, specifically the serotonergic and dopaminergic systems: Serotonin (5-HT), 5-hydroxyindolacetic acid (5-HIAA), 3,4-dihydroxyphenylacetic acid (DOPAC), dopamine (DA), 3-metoxytryptamin (3-MT) and homovanillic acid (HVA). Recognized for its speed and selectivity, HPLC enables direct analysis of intracerebral microdialysis samples without complex derivatization. Various chromatographic methods, including reverse phase (RP), are explored for neurotransmitters (NTs) and metabolites separation. Electrochemical detector (ECD), particularly with glassy carbon (GC) electrodes, is emphasized for its simplicity and sensitivity, aimed at enhancing reproducibility through optimization strategies such as modified electrode materials. This paper underscores the determination of limits of detection (LOD) and quantification (LOQ) and the linear range (L.R.) showcasing the potential for real-time monitoring of compounds concentrations. A non-exhaustive compilation of literature values for LOD, LOQ, and L.R. from recent publications is included.

Correlation Between Salivary, Platelet and Central Serotonin Levels in Children.

BACKGROUND: Serotonin (5-HT) is a neurotransmitter synthesized in both the central nervous system (CNS) and in enterochromaffin cells of the gut. 5-HT biosynthesis is separate between the periphery and the CNS. Any observed correlations between centrally and peripherally measured 5-HT remain to be elucidated. Previous efforts have looked for a noninvasive marker of central serotonin, including serotonin in whole blood, plasma, platelets, saliva, and urine; however, results are conflicting. AIM: Finding a noninvasive marker for central serotonin turnover that can be used for diagnosis and therapeutic monitoring in patients with primary neurotransmitter deficiencies. METHODS: Inclusion criterion was all children presenting with neurological symptoms whose clinical investigations included lumbar puncture (LP) for cerebrospinal fluid (CSF) collection and neurotransmitter metabolite analysis, were recruited. For central serotonin turnover, the serotonin metabolite 5-hydroxyindoleacetic acid (5HIAA) was used. Bivariate correlation between the serotonin levels in CSF (5HIAA), platelets, and saliva was calculated. RESULTS: Twenty-six patients (aged 6 months to 15 years) with various neurologic presentations had LP for CSF collection and neurotransmitter metabolite analysis as part of their clinical care. An additional salivary and blood sample was obtained at the same time. Eighteen patients had suitable samples for quantitative measure of serotonin. There was no correlation between platelet serotonin and CSF 5HIAA levels (Pearson's coefficient of correlation - PCC: 0.010) or between salivary serotonin and CSF 5HIAA (PCC: 0.258). There was a strong negative correlation between salivary and platelet serotonin (PCC: -0.679). CONCLUSION: Our findings suggest that salivary serotonin measurement is not a suitable noninvasive marker for measuring central serotonin turnover.

Investigation of the interaction between serotonin-related compounds and phenylboronate moieties in monolithic silica disk-packed spin columns.

Solid-phase extraction technologies are widely used for sample pretreatment in bioanalysis. Monolithic silica disk-packed spin columns modified with phenylboronate moieties have been developed for the selective extraction of cis-diol compounds such as catecholamines. However, in our preliminary studies, serotonin was found to also be extracted in this treatment, along with catecholamines. In this study, the interaction between serotonin-related compounds (serotonin, tryptophan, 5-hydroxy-tryptophan and 5-hydroxyindoleacetic acid) and phenylboronate moieties was investigated. We found that only serotonin was extracted with phenylboronate-modified monolithic silica, whereas tryptophan, 5-hydroxy-tryptophan and 5-hydroxyindoleacetic acid were not. Hydrophobic interactions rather than ionic interactions were the primary factor for the adsorption of serotonin to phenylboronate. Finally, the selective pretreatment procedure for catecholamines was improved: thus, the method could be applied for the pretreatment of bio-samples.

Specific Urinary Metabolites in Malignant Melanoma.

Background and objectives: Melanin, which has a confirmed role in melanoma cell behaviour, is formed in the process of melanogenesis and is synthesized from tryptophan, L-tyrosine and their metabolites. All these metabolites are easily detectable by chromatography in urine. Materials and Methods: Urine samples of 133 individuals (82 malignant melanoma patients and 51 healthy controls) were analysed by reversed-phase high-performance liquid chromatography (RP-HPLC). The diagnosis of malignant melanoma was confirmed histologically. Results: Chromatograms of melanoma patients showed increased levels of 5,6-dihydroxyindole-2-carboxylic acid, vanilmandelic acid, homovanilic acid, tryptophan, 5-hydroxyindole-3-acetic acid, and indoxyl sulphate compared to healthy controls. Concentration of indoxyl sulphate, homovanilic acid and tryptophan were significantly increased even in the low clinical stage 0 of the disease (indoxyl sulphate, homovanilic acid and tryptophan in patients with clinical stage 0 vs. controls expressed as medium/ interquartile range in µmol/mmol creatinine: 28.37/15.30 vs. 5.00/6.91; 47.97/33.08 vs. 7.33/21.25; and 16.38/15.98 vs. 3.46/6.22, respectively). Conclusions: HPLC detection of metabolites of L-tyrosine and tryptophan in the urine of melanoma patients may play a significant role in diagnostics as well as a therapeutic strategy of melanoma cancer.

Concurrent quantification of tryptophan and its major metabolites.

An imbalance in tryptophan (TRP) metabolites is associated with several neurological and inflammatory disorders. Therefore, analytical methods allowing for simultaneous quantification of TRP and its major metabolites would be highly desirable, and may be valuable as potential biomarkers. We have developed a HPLC method for concurrent quantitative determination of tryptophan, serotonin, 5-hydroxyindoleacetic acid, kynurenine, and kynurenic acid in tissue and fluids. The method utilizes the intrinsic spectroscopic properties of TRP and its metabolites that enable UV absorbance and fluorescence detection by HPLC, without additional labeling. The origin of the peaks related to analytes of interest was confirmed by UV-Vis spectral patterns using a PDA detector and mass spectrometry. The developed methods were validated in rabbit fetal brain and amniotic fluid at gestational day 29. Results are in excellent agreement with those reported in the literature for the same regions. This method allows for rapid quantification of tryptophan and four of its major metabolites concurrently. A change in the relative ratios of these metabolites can provide important insights in predicting the presence and progression of neuroinflammation in disorders such as cerebral palsy, autism, multiple sclerosis, Alzheimer disease, and schizophrenia.

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.

Understanding common population markers for SARS-CoV-2 RNA normalization in wastewater - A review.

Wastewater monitoring and epidemiology have seen renewed interest during the recent COVID-19 pandemic. As a result, there is an increasing need to normalize wastewater-derived viral loads in local populations. Chemical tracers, both exogenous and endogenous compounds, have proven to be more stable and reliable for normalization than biological indicators. However, differing instrumentation and extraction methods can make it difficult to compare results. This review examines current extraction and quantification methods for ten common population indicators: creatinine, coprostanol, nicotine, cotinine, sucralose, acesulfame, androstenedione 5-hydroindoleacetic acid (5-HIAA), caffeine, and 1,7-dimethyluric acid. Some wastewater parameters such as ammonia, total nitrogen, total phosphorus, and daily flowrate were also evaluated. The analytical methods included direct injection, dilute and shoot, liquid/liquid, and solid phase extraction (SPE). Creatine, acesulfame, nicotine, 5-HIAA and androstenedione have been analysed by direct injection into LC-MS; however, most authors prefer to include SPE steps to avoid matrix effects. Both LC-MS and GC-MS have been successfully used to quantify coprostanol in wastewater, and the other selected indicators have been quantified successfully with LC-MS. Acidification to stabilize the sample before freezing to maintain the integrity of samples has been reported to be beneficial. However, there are arguments both for and against working at acidic pHs. Wastewater parameters mentioned earlier are quick and easy to quantify, but the data does not always represent the human population effectively. A preference for population indicators originating solely from humans is apparent. This review summarises methods employed for chemical indicators in wastewater, provides a basis for choosing an appropriate extraction and analysis method, and highlights the utility of accurate chemical tracer data for wastewater-based epidemiology.

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.

Application of Wastewater-Based Epidemiology for Tracking Human Exposure to Deoxynivalenol and Enniatins.

Wastewater-based epidemiology (WBE) is a promising biomonitoring approach with the potential to provide direct information on human intake and exposure to food contaminants and environmental chemicals. The aim of this study was to apply WBE while employing the normalization method for exploring human exposure to selected mycotoxins according to population biomarker 5-hydroxyindoleacetic acid (5-HIAA). This type of normalization technique has been previously used to detect various other compounds. However, to the best of our knowledge, this is the first study tracking human exposure to mycotoxins. A sensitive analytical methodology was developed to achieve reliable quantification of deoxynivalenol, enniatins, and beauvericin in wastewater (WW) samples. The applicability of the method was evaluated by testing 29 WW samples collected at WW treatment plants in Latvia. With frequency of detection greater than 86%, enniatins B, B1, A, and A1 were revealed in WW samples. The estimated total daily intake for enniatins was in the range of 1.8-27.6 µg/day per person. Free deoxynivalenol (DON) was determined in all analysed WW samples. Based on the average 5-HIAA excretion level and the determined 5-HIAA content in the samples, the intake of DON by the human population of Riga was estimated at 325 ng/kg b.w. day.

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.

Tetraphenylpyrazine-Based Luminescent Metal-Organic Framework for Chemical Sensing of Carcinoids Biomarkers.

A new non-interpenetrated three-dimensional (3D) pillared-layered TPP-based LMOF [Zn3(TPyTPP)0.5(BDC)3]·8DMF (denoted as Zn-MOF 1) was successfully prepared (TPyTPP = tetrakis(4-(pyridin-4-yl)phenyl)pyrazine and H2BDC = 1,4-benzenedicarboxylic acid). Zn-MOF 1 was characterized by single-crystal X-ray diffraction, PXRD, IR, N2 adsorption, thermogravimetric analysis, and luminescent spectrum. Impressively, luminescent sensing studies reveal that activated Zn-MOF 1 not only displays excellent luminescence-quenching efficiency with the values of high Ksv and low LODs toward 5-hydroxytryptamine (5-HT) and 5-hydroxyindole-3-acetic acid (5-HIAA), respectively, but also possesses outstanding sensing characteristics in terms of fast response, high sensitivity, and specific selectivity. Zn-MOF 1 performs as efficient sensing of carcinoid biomarkers to provide a fresh detection platform for the diagnosis of carcinoids. In addition, the sensing mechanism was also explored on the basis of ultraviolet-visible (UV-vis) absorption, DFT calculations, and structural analysis.

Nutritional up-regulation of serotonin paradoxically induces compulsive behavior.

Dietary etiologies or treatments for complex mental disorder are highly controversial in psychiatry. Nevertheless, diet affects brain chemistry (particularly serotonin), and can reduce abnormal behavior in humans and animals. We formulated a diet that elevated brain serotonin and tested whether it would reduce hair pulling in a mouse model of trichotillomania. In a double-blind crossover trial, dietary elevation of brain serotonin unexpectedly increased hair pulling (P = 0.0006) and induced ulcerative dermatitis (UD; P = 0.001). The causative agent for UD is unknown. Therefore, we fed the treatment diet to a second group of mice to test whether UD is behavioral in origin. The diet increased scratching behavior (P < 0.0001). However, high scratching behavior (P = 0.027) and low barbering (P = 0.040) prior to treatment predicted the development of UD. Thus diet can trigger the onset of a complex disorder in the absence of an underlying metabolic deficit. Furthermore, we propose UD as model of compulsive skin-picking.

Brainstem serotonergic deficiency in sudden infant death syndrome.

CONTEXT: Sudden infant death syndrome (SIDS) is postulated to result from abnormalities in brainstem control of autonomic function and breathing during a critical developmental period. Abnormalities of serotonin (5-hydroxytryptamine [5-HT]) receptor binding in regions of the medulla oblongata involved in this control have been reported in infants dying from SIDS. OBJECTIVE: To test the hypothesis that 5-HT receptor abnormalities in infants dying from SIDS are associated with decreased tissue levels of 5-HT, its key biosynthetic enzyme (tryptophan hydroxylase [TPH2]), or both. DESIGN, SETTING, AND PARTICIPANTS: Autopsy study conducted to analyze levels of 5-HT and its metabolite, 5-hydroxyindoleacetic acid (5-HIAA); levels of TPH2; and 5-HT(1A) receptor binding. The data set was accrued between 2004 and 2008 and consisted of 41 infants dying from SIDS (cases), 7 infants with acute death from known causes (controls), and 5 hospitalized infants with chronic hypoxia-ischemia. MAIN OUTCOME MEASURES: Serotonin and metabolite tissue levels in the raphé obscurus and paragigantocellularis lateralis (PGCL); TPH2 levels in the raphé obscurus; and 5-HT(1A) binding density in 5 medullary nuclei that contain 5-HT neurons and 5 medullary nuclei that receive 5-HT projections. RESULTS: Serotonin levels were 26% lower in SIDS cases (n = 35) compared with age-adjusted controls (n = 5) in the raphé obscurus (55.4 [95% confidence interval {CI}, 47.2-63.6] vs 75.5 [95% CI, 54.2-96.8] pmol/mg protein, P = .05) and the PGCL (31.4 [95% CI, 23.7-39.0] vs 40.0 [95% CI, 20.1-60.0] pmol/mg protein, P = .04). There was no evidence of excessive 5-HT degradation assessed by 5-HIAA levels, 5-HIAA:5-HT ratio, or both. In the raphé obscurus, TPH2 levels were 22% lower in the SIDS cases (n = 34) compared with controls (n = 5) (151.2% of standard [95% CI, 137.5%-165.0%] vs 193.9% [95% CI, 158.6%-229.2%], P = .03). 5-HT(1A) receptor binding was 29% to 55% lower in 3 medullary nuclei that receive 5-HT projections. In 4 nuclei, 3 of which contain 5-HT neurons, there was a decrease with age in 5-HT(1A) receptor binding in the SIDS cases but no change in the controls (age x diagnosis interaction). The profile of 5-HT and TPH2 abnormalities differed significantly between the SIDS and hospitalized groups (5-HT in the raphé obscurus: 55.4 [95% CI, 47.2-63.6] vs 85.6 [95% CI, 61.8-109.4] pmol/mg protein, P = .02; 5-HT in the PGCL: 31.4 [95% CI, 23.7-39.0] vs 71.1 [95% CI, 49.0-93.2] pmol/mg protein, P = .002; TPH2 in the raphé obscurus: 151.2% [95% CI, 137.5%-165.0%] vs 102.6% [95% CI, 58.7%-146.4%], P = .04). CONCLUSION: Compared with controls, SIDS was associated with lower 5-HT and TPH2 levels, consistent with a disorder of medullary 5-HT deficiency.

A sensitive analytical method for the measurement of neurotransmitter metabolites as potential population biomarkers in wastewater.

Wastewater-based epidemiology is a growing research field which provides valuable information on community drug use and chemical exposure. One parameter critical to estimations of drug use is the catchment area population. A population biomarker could be used to provide this information. This study evaluated the analytical suitability of three endogenous biomarkers of human activity: the serotonin metabolite 5-hydroxyindoleacetic acid (5-HIAA) which has previously been proposed and two further candidates, the catecholamine metabolites vanillylmandelic acid (VMA) and homovanillic acid (HVA). An analytical method involving derivatization was developed and validated for two candidates, 5-HIAA and HVA by liquid chromatography - mass spectrometry. The best performance was obtained for VMA as the underivatized analyte. The derivatized extracts produced a 100 times better sensitivity. The three neurotransmitter metabolites were evaluated as population biomarkers in wastewater samples. All were stable in sample, not lost upon filtration and showed stable inter-day mass loads over seven days for a metropolitan wastewater treatment plant. When applied to a small community during a festival period, mass loads of both HVA and VMA reflected the increase in the catchment population, whilst 5-HIAA proved to be more variable.

Physiological responses during acute stress recovery depend on stress coping style in European sea bass, Dicentrarchus labrax.

Individual stress coping style (reactive, intermediate and proactive) was determined in 3 groups of 120 pit tagged European seabass using the hypoxia avoidance test. The same three groups (no change in social composition) were then reared according to the standards recommended for this species. Then, 127 days later, individuals initially characterized as reactive, intermediate or proactive were submitted to an acute confinement stress for 30 min. Blood samples were taken to measure plasma cortisol levels 30 min (Stress30) or 150 min (Stress150) after the end of the confinement stress. Individuals were then sacrificed to sample the telencephalon in order to measure the main monoamines and their catabolites (at Stress30 only). Individuals from Stress150 were sampled for whole brain for a transcriptomic analysis. The main results showed that reactive individuals had a lower body mass than intermediate individuals which did not differ from proactive individuals. The physiological cortisol response did not differ between coping style at Stress30 but at Stress150 when intermediate and proactive individuals had recovered pre stress levels, reactive individuals showed a significant higher level illustrating a modulation of stress recovery by coping style. Serotonin turnover ratio was higher in proactive and reactive individuals compared to intermediate individuals and a significant positive correlation was observed with cortisol levels whatever the coping style. Further, the confinement stress led to a general increase in the serotonin turnover comparable between coping styles. Stress150 had a significant effect on target mRNA copy number (Gapdh mRNA copy number decreased while ifrd1 mRNA copy number increased) and such changes tended to depend upon coping style.

Serotonin: release in the forebrain by stimulation of midbrain raphé.

Electrical stimulation of the midbrain raphé, an area in which neuronal perikarya containing serotonin are aggregated, produces an increase in 5-hydroxyindoleacetic acid and a decrease in serotonin in the forebrain. These changes indicate that serotonin in the brain can be released via a specific neural pathway, namely, the system of axons projecting into the forebrain from serotonin-containing neurons in the midbrain raphé.

Narcolepsy: biogenic amine deficits in an animal model.

Concentrations of biogenic amine metabolites in discrete brain areas differed significantly between dogs with genetically transmitted narcolepsy and age- and breed-matched controls. Dopamine and 3,4-dihydroxyphenylacetic acid were consistently elevated in the brains of narcoleptic animals, while homovanillic acid was not. Narcoleptic animals consistently exhibited lower utilization of dopamine and higher intraneuronal degradation of dopamine but no uniform decrease in serotonin utilization. Hence neuropathology appears to be associated with genetically transmitted canine narcolepsy. The data indicate a nonglobal depression of dopamine utilization or turnover or both.

Facilitated sexual behavior reversed and serotonin restored by raphe nuclei transplanted into denervated hypothalamus.

Fetal raphe cells transplanted into the hypothalamus reversed facilitation of feminine sexual behavior in rats with brain lesions induced by 5,7-dihydroxytryptamine. Immunocytochemical and chemical analyses of serotonin indicate that reinnervation of the ventromedial nucleus of the hypothalamus by the transplants is associated with behavioral recovery. The findings suggest that transplanted fetal tissue can exert functional regulation over an innate, complex, hormone-dependent behavior in adult rats.

Origin of 5-hydroxyindoleacetic acid in the spinl fluid.

5-Hydroxyindoleacetic acid applied intracisternally in cats does not appear in spinal fluid. Changes of 5-hydroxyindoleacetic acid concentration in the spinal cord are clearly reflected in the perfusate of the spinal subarachnoid space. Thus, 5-hydroxyindoleacetic acid in the spinal fluid originates from the spinal cord and reflects metabolic changes of 5-hydroxytryptamine in the spinal tissue, but not those in the brain.

Persistent increase in brain serotonin turnover after chronic administration of LSD in the rat.

Lysergic acid diethylamide at doses of 20 micrograms per kilogram per day was administered orally to rats for I month. Eighteen hours after the final dose a 25 to 30 percent increase in the synthesis and turnover of serotonin was noted, as well as a moderate but significant increase in the concentration of tryptophan (18 percent) and serotonin (13 percent) in the brain.