Probenecid: Dosage,levels in plasma and cerebrospinal fluid (CSF) and influence upon CSF levels of homovanillic acid (HVA) and 5-hydroxyindoleacetic acid (5-HIAA) in the rabbit

Probenecid retards the efflux of acid monoamine metabolites from the brain tissue and CSF to the blood. The probenecid-induced accumulation of these metabolites is held to be indicative of the turnover rate of the corresponding amines. Although the penetration of probenecid into the CSF does not proceed at a constant rate, Korf et al. (1972) and Sjöstrom (1972) have shown a correlation between CSF levels of probenecid and that of HVA and 5-HIAA. In this study an attempt was made to establish the relationship between doses of probenecid and levels of this compound in plasma and CSF; between levels in plasma and CSF; and between CSF levels of probenecid and of HVA and 5-HIAA. This study was performed in a homogeneous group of laboratory rabbits.All correlations proved to be significant. The implications of these results for studies using the probenecid technique are discussed.     

5-Hydroxyindole acetic acid and homovanillic acid in cerebrospinal fluid in manic-depressive psychosis and the effect of probenecid treatment

Summary The increased concentrations of 5-hydroxyindole acetic acid and homovanillic acid produced in cerebrospinal fluid by probenecid has been investigated in 15 manic-depressive patients and 21 psychiatric control patients, and has been related to the concentrations of probenecid in the CSF. The pharmacokinetics of probenecid were the same in the manic-depressive patients and the controls, as judged by its concentrations in plasma (bound and free) and CSF after a standard oral dose p.o., and by measurements of half-life and volume of distribution after intravenous injection. — The manic-depressive patients had lower concentrations of 5-HIAA and HVA than controls at similar CSF concentrations of probenecid; this was concluded from results with pairs of patients matched with regard to probenecid in CSF, and from differences between the patients and controls in the slopes of the regression lines for probenecid in CSF against 5-HIAA/HVA. The differences in 5-HIAA/HVA between the diagnostic groups were greater with increasing concentrations of probenecid in CSF; and, with concentrations of probenecid in CSF>1.0 µg/ml, by using the 5HIAA concentrations it was possible to classify the patients correctly into their diagnostic groups in 92% of cases.     

Probenecid-induced accumulation of 5-hydroxyindoleacetic acid and homovanillic acid in rat brain

The accumulation of 5-hydroxyindoleacetic acid (5-HIAA) and homovanillic acid (HVA) in rat brain has been examined after probenecid infusion over 8 h. At plasma probenecid concentrations of 200-400 micrograms mL-1 a steady state level in the accumulation of 5-HIAA and HVA was achieved, the increase above the endogenous levels being 135% and 65%, respectively. When the plasma concentration of probenecid rose above 400 micrograms mL-1 there was further accumulation of both 5-HIAA and HVA probably induced by increased neuronal activity or toxicity due to probenecid. The explanation for the plateau of 5-HIAA and HVA obtained over the plasma probenecid concentration interval of 200-400 micrograms mL-1 could be that the levels were reached when there was complete inhibition of active transport, and when the rate of formation of the metabolites equalled the rate of elimination by alternative routes i.e. bulk flow and diffusion. Therefore when probenecid is used to inhibit the active transport of acid monoamine metabolites across the blood-brain barrier, its plasma concentration should be within the range of 200-400 micrograms mL-1.     

Quantitation of CSF concentrations and biological activity of probenecid metabolites

Summary The concentrations of probenecid and four of its metabolites have been examined in plasma and CSF by electron capture gas chromatography after extractive methylation. The plasma concentration of each of the metabolites was in the range 1,5–15 µg/ml and constituted less than 10% of the parent compound. The penetration into CSF of the metabolites was lower than that of probenecid. The concentration of each of the metabolites was below 0,2 µg/ml and the total concentration never exceeded 10% of the probenecid concentration. The inhibitory effect of the metabolites on uptake was tested in rabbit renal cortex using³H-p-amino-hippuric acid. The inhibitory effect was low. From the low activity and relatively low concentrations of the metabolites in CSF it is concluded that probenecid metabolites do not contribute to the probenecid-induced blocking effect of acid transport from the CSF.     

The influence of probenecid on the metabolism of serotonin,dopamine and their precursors in man

Probenecid inhibits the efflux of acid monoamine (MA) metabolites from the CNS. The probenecid-induced accumulation of these metabolites in the CSF in man supplies data on the central turnover of the corresponding amines. In this study an attempt was made to establish whether probenecid also exerts an influence on the metabolism of the MA precursors: tryptophan and tyrosine. The principal conclusions were the following.

1. Whereas in rats probenecid lowers the serum tryptophan level and elevates that in the brain (probably as a result of interference with the binding of tryptophan to serum albumins), the serum tryptophan level in human individuals is also lowered but the CSF concentration remains unchanged. After an oral tryptophan load, however, the CSF tryptophan concentration does increase.It is suggested that in man, endogenously released and exogenous tryptophan enter different metabolic pools in the brain.
2. After an oral load of 1-tryptophan, for the most part depressive patients showed a more rapid increase in CSF tryptophan concentration and a less marked rise of the CSF 5-HIAA level than did the psychologically undisturbed test subjects examined by Eccleston et al. It seems possible that, in the depressive patient, the tryptophan-metabolizing capacity is disturbed.
3. After an oral load of 1-tryptophan the CSF HVA concentration increased. Possibly, tryptophan is transformed to 5-HT in dopaminergic neurons, and this 5-HT may supersede the DA from the storage sites. This effect may well be of significance in the therapeutic application of 5-HT precursors.
4. The CSF concentrations of 5-HIAA, HVA, tryptophan and tyrosine show no systematic variations during the day.

     

5-hydroxyindoleacetic acid (and homovanillic acid) levels in the cerebrospinal fluid after probenecid application in patiens with manic-depressive psychosis

Summary Probenecid was administered to 17 depressed, 19 manic and 15 control patients and further to 11 healthy volunteers. Before and after the administration the levels of 5-hydroxyindoleacetic acid (5-HIAA) were determined in cerebrospinal fluid (CSF). In six of the depressed, seven of the manic and seven of the patients from the group of controls and volunteers also homovanillic acid (HVA) was determined in CSF. After the application of probenecid there is a significant increase in 5-HIAA and HVA in the control patients and healthy volunteers but not in the depressed and manic patients. No increase in HVA occurred in the depressed patients but in the manic ones the HVA values were almost as high as in the group of controls and healthy volunteers. It is suggested that the lack of increase in 5-HIAA and HVA after probenecid indicates an inhibition of the synthesis of the acids and thus of the corresponding amines (5-hydroxytryptamine and dopamine) in the brain.     

Influence of convulsive therapy on 5-hydroxyindoleacetic acid and homovanillic acid in cerebrospinal fluid in endogenous depression

The cerebrospinal fluid (CSF) levels of 5-hydroxyindoleacetic acid (5-HIAA) and homovanillic acid (HVA) were determined in 20 patients with endogenous depression before and 2–6 days after a full course of convulsive therapy, the depressive symptoms being simultaneously rated.

1. The level of 5-HIAA was similar to that in previous series of healthy controls while the level of HVA appeared somewhat low.
2. The levels did not change after therapy in spite of considerable clinical improvement.
3. There was no relation between the levels and the severity of the depressive state, nor between changes of the levels and degree of clinical improvement.
4. There was no relation between the levels and the severity of the depressive state, nor between changes of the levels and degree of clinical improvement.

The validity of determination of acid monoamine metabolites in CSF relative to the cerebral turn-over of the amines may be increased, if the elimination of metabolites from CSF is blocked with probenecid.     

Increase in the plasma concentration of free tryptophan caused by probenecid in humans

Probenecid was administered orally in a dose of 1 g twice daily for 3 days to eight patients nutriated through a gastric tube with a standarized diet containing a known amount of tryptophan. Probenecid caused an increase by 52% (P<0.01) in the free (non protein-bound) concentration of tryptophan in plasma (from 1.22±0.16 to 1.86±0,28 g/ml; mean±SEM). The total (free + protein-bound) plasma tryptophan concentration was not significantly changed by the present dose of probenecid. There was a positive correlation (Spearmans rank correlation coefficient =0.74; P<0.05) between the increase in percentage free tryptophan and the achieved plasma concentration of probenecid. The cerebrospinal fluid (CSF) concentration of tryptophan was not significantly changed by probenecid (2 g/day during 21/2 days) given to another group of five patients.It is concluded from the present study, that the increase in the CSF concentration of 5-hydroxyindoleacetic acid (5-HIAA) caused by probenecid, in addition to blockade of the 5-HIAA transport out of the CSF, might be explained by an increased rate of synthesis of brain serotonin since the availability of its precursor is increased due to the probenecid-induced increase in the plasma concentration of free tryptophan.     

Cerebrospinal fluid 5-hydroxyindoleacetic acid (5HIAA) and homovanillic acid (HVA) following probenecid in unipolar depressives treated with amitriptyline

Lumbar cerebrospinal fluid 5-HIAA, HVA, and the ratio 5-HIAA/HVA were measured followed probenecid administration in eleven patints with unipolar depression before and during treatment with amitriptyline (AMI). Control values were obtained from a group of inmate volunteers. Prior to treatment CSF 5HIAA formation in the depressives was not different from controls. During treatment with AMI, CSF 5-HIAA formation decreased. One patient with psychotic symptoms prior to AMI and two patients who developed psychotic reactions on AMI showed relatively low CSF 5HIAA formation prior to antidepressant therapy. Compared to controls CSF HVA values were higher in the depressives prior to AMI therapy.     

The effect of olanzapine treatment on monoamine metabolite concentrations in the cerebrospinal fluid of schizophrenic patients.

The mechanism of action of both typical antipsychotics and the atypical antipsychotic, clozapine, may be related to the (changing) interaction of dopamine and serotonin in schizophrenia. This study examined the effect of olanzapine in schizophrenic patients on cerebrospinal fluid (CSF) metabolites of dopamine (homovanillic acid, HVA) and serotonin (5-hydroxyindoleacetic acid, 5-HIAA). Twenty-three male schizophrenic patients, who were drug-free for at least 2 weeks (mean drug-free period of 35 days +/- 43; median 16 days), underwent a lumbar puncture (LP). Patients were subsequently treated with olanzapine 10 mg/day for 6 weeks, after which the LP was repeated. CSF was assayed for HVA and 5-HIAA concentrations. Psychiatric symptoms were rated once a week. Olanzapine significantly increased HVA concentrations and the HVA/5-HIAA ratio while 5-HIAA concentrations were not altered. These changes did not significantly correlate with treatment response. A negative correlation was found between HVA concentrations and negative symptoms after olanzapine treatment. In conclusion, olanzapine treatment increases HVA concentrations and the HVA/5-HIAA ratio in CSF of schizophrenic patients, but these changes are unrelated to its clinical efficacy.     

Neurochemistry of withdrawal emergent symptoms in children

The probenecid procedure was used to study the metabolite accumulations of dopamine (DA) and serotonin (5-HT) in the cerebrospinal fluid (CSF) of 11 children receiving chronic neuroleptic therapy. Specimens were obtained while the children were being given chronically prescribed medication (Condition 1) and again 3–4 weeks later, following the discontinuation of drugs (Condition 2). At that time, five children showed typical dyskinetic withdrawal emergent symptoms (WES) and six were free of symptoms. CSF specimens were also obtained from eight drug-free children, diagnosed as having chronic organic brain disease, who served as a contrast population against which the findings were evaluated. CSF accumulations of 5-hydroxyindoleacetic acid (5-HIAA) and homovanillic acid (HVA) did not differentiate the drug-treated children who showed WES from those who did not manifest these symptoms. A significant decrease in 5-HIAA was found in Condition 2, suggesting that chronic treatment with neuroleptics may effect 5-HT metabolism in children. The contrast population was found to have lower CSF concentrations of probenecid and were consequently of little help in clarifying the nature of the 5-HIAA decrement. A number of serious deficiences were noted regarding the use of the probenecid procedure, and it is felt that the use of spinal taps for studying neuroleptic effects on brain metabolism in children is unlikely to provide important information with regard to either CNS drug actions or toxicity.     

Stereoselective metabolism of citalopram in plasma and cerebrospinal fluid of depressive patients: relationship with 5-HIAA in CSF and clinical response

Plasma and cerebrospinal fluid (CSF) concentrations of the enantiomers of citalopram (CIT), its N-demethylated metabolite demethylcitalopram (DCIT) and its deaminated metabolite citalopram propionic acid derivative (CIT-PROP) were measured in plasma and CSF in 22 depressed patients after a 4-week treatment with 40 mg/d citalopram, which was preceded by a 1-week washout period. CSF 5-hydroxyindoleacetic acid (5-HIAA) and homovanillic acid (HVA) were measured at baseline and after the 4-week CIT medication period. Patients were assessed clinically, using the Hamilton Depression Rating Scale (21-item HAM-D): at baseline and then at weekly intervals. CSF concentrations of S-CIT and R-CIT were 10.6 +/- 4.3 and 20.9 +/- 6 ng/mL, respectively, and their CSF/plasma ratios were 52% +/- 9% and 48% +/- 6%, respectively. The CIT treatment resulted in a significant decrease (28%) of 5-HIAA (P < 0.0001) and a significant increase (41%) of HVA in the CSF. Multiple linear regression analyses were performed to identify the impact of plasma and CSF CIT enantiomers and its metabolites on CSF monoamine metabolites and clinical response. There were 10 responders as defined by a > or =50% decrease of the HAM-D score (DeltaHAM-D) after the 4-week treatment. DeltaHAM-D correlated (Spearman) significantly with CSF S-CIT (r = - 0.483, P < 0.05), CSF S-CIT-PROP (r = -0.543, P = 0.01) (a metabolite formed from CIT by monoamine oxidase [MAO]) and 5-HIAA decrease (Delta5-HIAA) (r = 0.572, P = 0.01). The demonstrated correlations between pharmacokinetic parameters and the clinical outcome as well as 5-HIAA changes indicate that monitoring of plasma S-CIT, CSF S-CIT and CSF S-CIT-PROP may be of clinical relevance.     

马桑内酯对麻醉狗脑脊液中单胺类神经递质代谢物含量影响的初步探讨

作者通过狗口服丙磺舒阻断酸性物质向外周血循环转运的方法来测定肌注马桑内酯1mg/kg,前、后脑脊液中去甲肾上腺素、多巴胺和5-羟色胺的代谢物3-甲氧-4羟苯一乙二醇、高香草酸和5-羟吲哚乙酸的含量改变,以了解三者的更新率。初步结果表明:高香草酸的含量显著下降(P<0.05),5-羟吲哚乙酸的含量有所下降(P>0.05)但无统计学意义,3-甲氧-4羟苯一乙二醇影响不大。     

Individual differences in basal cisternal cerebrospinal fluid 5-HIAA and HVA in monkeys. The effects of gender, age, physical characteristics, and matrilineal influences.

We examined the effects of gender, age, weight, length, body shape (ectomorphy), and matrilineal influences on cisternal cerebrospinal fluid 5-hydroxyindoleacetic acid (CSF 5-HIAA) and homovanillic acid (HVA) in 78 socially living adult and adolescent vervet monkeys. CSF 5-HIAA and the 5-HIAA:HVA ratio were higher (by 27% and 18%, respectively) in females. In both sexes, CSF 5-HIAA and the 5-HIAA:HVA ratio increased with age. Neither weight nor length were independently related to CSF 5-HIAA or HVA; however, shape correlated with CSF 5-HIAA and HVA in males (higher in thin, long subjects). Male offspring had CSF 5-HIAA concentrations and 5-HIAA:HVA ratios that were significantly closer to their mothers than did age-matched, maternally unrelated males. Repeated measures of CSF 5-HIAA and HVA in another 22 males living in unvarying settings showed that individual differences in these measures persisted over time. The data underscore the impact of gender, age, and matrilineal relationships on individual differences in CSF monoamine metabolites and highlight the importance of controlling for age and gender in neuropharmacological investigations of clinical populations.     

Vasopressin in CSF and plasma in depressed suicide attempters: preliminary results.

Increased plasma arginine vasopressin (AVP) concentrations have been reported in depressed suicide attempters. Plasma AVP is primarily produced by the magnocellular system in response to increased plasma osmolality, and central AVP may be independently regulated. In the present study we investigated cerebrospinal fluid (CSF) and plasma AVP concentrations in depressed patients and controls. Nineteen drug-free depressed psychiatric inpatients (nine suicide attempters) and nine neurological control subjects underwent lumbar puncture and psychiatric evaluation. CSF and plasma concentrations of AVP, serotonin (5-HT), 5-hydroxyindoleacetic acid (5-HIAA), homovanillic acid (HVA), and cortisol were assayed. In 15 depressed patients (eight suicide attempters), the combined dexamethasone/corticotropin-releasing hormone (Dex/CRH) test was performed to examine the hypothalamic-pituitary-adrenocortical (HPA) system. There were no differences between depressed subjects and controls in all parameters measured. Suicide attempters did not differ from nonattempters. In depressed patients, plasma AVP correlated positively with cortisol. There was no relationship between CSF AVP and monoamine metabolites in CSF.     

Absence of effect of para-chlorophenylalanine on 5-hydroxyindoleacetic acid in cerebrospinal fluid in man

The effect of para-chlorophenylalanine (PCPA) on the 5-hydroxy-indoleacetic acid (5-HIAA) content in human cerebrospinal fluid (CSF) has been studied. There was no effect on the CSF-content of 5-HIAA 12, 24 or 48 h after a single dose of PCPA 1 g p.o. Neither was there any effect after 1 g/day during 4 days. The increase of 5-HIAA after administration of probenecid was reduced during treatment with PCPA 1 g/day. This reduction, however, is not due to a diminished production of 5-HIAA by PCPA but probably caused by a pharmacological interaction between probenecid and PCPA since the concentrations of probenecid in CSF were lower during administration of PCPA than without that drug.It is concluded that PCPA in the doses used in this study gives no effects on the CSF-concentrations of 5-HIAA.     

Effect of ECT and imipramine treatment on the concentration of 5-hydroxyindoleacetic acid (5HIAA) and homovanillic acid (HVA) in the cerebrospinal fluid of depressed patients

The influence of probenecid administration on 5HIAA and HVA concentrations in the CSF of depressed patients, was studied before and after treatment with imipramine or ECT.The average increase of the two metabolites in the CSF after probenecid was similar in the untreated depressed patients and in the same patients improved after both imipramine or ECT treatment.The treatment determined a significant increase in the CSF concentration of the acid metabolites also before the probenecid administration.     

Effect of α-methyl fluorodopa on dopamine metabolites: Importance of conjugation and egress

The effects of D,L-α-monofluoromethyldopa (MFMD), an inhibitor of aromatic L-amino acid decarboxylase, on the metabolism of dopamine (DA) and 5-hydroxytryptamine was investigated using rat brain and cerebrospinal fluid (CSF). Vehicle or MFMD (100 mg/kg) was given p.o. and 16 h later probenecid (200 mg/kg i.p.). CSF was sampled and the rats killed immediately or after 1 h. Vehicle treated rats showed regional differences of percentage conjugation of DA metabolites: 3,4-dihydroxyphenylacetic acid (DOPAC), striatum 10%, rest of brain 45%, CSF 67%; homovanillic acid (HVA), striatum 20%, rest of brain 35%, CSF 53%. These differences and the proportionately greater increases of conjugates than of free acids after probenecid vitiate regional comparisons of DA metabolism if conjugates are not included. MFMD alone decreased neither 5HIAA (except in the striatum) nor the free DA metabolites but decreased both conjugates in CSF and conjugated DOPAC in rest of brain. The inhibitory effects of MFMD on 5HT and DA synthesis were most evident when measured by the accumulation of 5HIAA or total (DOPAC + HVA) after giving probenecid. MFMD may also inhibit amine metabolite egress and the conjugation of DOPAC and HVA.     

Effects of 2,4-dichlorophenoxyacetic acid (2,4-D) on biogenic amines and their acidic metabolites in brain and cerebrospinal fluid of rats

Effects of single subcutaneous doses of sodium 2,4-dichlorophenoxyacetate (2,4-D-Na) on biogenic amines and their acidic metabolites in rat brain and cerebrospinal fluid (CSF) were analyzed by high pressure liquid chromatography. After 200 mg/kg 2,4-D-Na, the cerebral concentration of 5-hydroxytryptamine (5-HT) was increased slightly and that of 5-hydroxyindoleacetic acid (5-HIAA) roughly 3-fold between 1 and 8 h after the administration. There was also a tendency towards slightly lowered dopamine (DA) levels. No statistically significant changes in brain concentrations of noradrenaline (NA), 3,4-dihydroxyphenylacetic acid (DOPAC), homovanillic acid (HVA) or tryptophan (TRY) were found. At the same time, however, the maximal increase in DOPAC, HVA and 5-HIAA concentrations in the CSF was 2.3–5.8-fold. The dependency of biogenic amines and metabolites on 2,4-D-Na dose was studied by injecting s.c. 0, 10, 30 and 100 mg/kg and sacrificing the rats at 2 h. In the brain, there was a dose-dependent increase in concentrations of 5-HIAA (at the two highest doses) and HVA (at the highest dose) while in the CSF those of all three acidic metabolites increased at the two highest doses. The 10 mg/kg dose had no effect. The results agree with the hypothesis that 2,4-D inhibits the organic acid transport out of the brain, which should then result in increased cerebral levels of acidic metabolites of biogenic amines, but it may also have effects on the activity of serotoninergic and dopaminergic neurones.     

Lidocaine selectively diminishes medullary serotonin metabolism in the rat

Serotonergic (5-HT) neurons of the nucleus raphe respond to modulation of segmental pathways. To explore lidocaine's ability to alter this response rats were injected with lidocaine 30 minutes before sacrifice. In some experiments, probenecid (200 mg/kg) was given before lidocaine to accumulate neuro transmit ter metabolites in the CNS. Probenecid significantly increased homovanillic acid (HVA) and 5-hydroxyindoleacetic acid (5-HIAA) levels in the striatum (+54% & + 33% respectively) and 5-HIAA in the medulla (+81%). Lidocaine had no effect on these probenecid-induced increases in striatal metabolites, yet significantly reduced production of medullary 5-HIAA (−58%, P = .008), but not MHPG (3-methoxy-4-hydroxγ-phenethyleneglycol). The reduced metabolism of descending 5-HT neurons suggests a CNS response to diminished segmental input. The anti-arrhythmic action of lidocaine may include an ability to quiet hyperactive sympathetic afferents from the heart.