Increased HVA levels in primate ventricular CSF following amphetamine administration

Dopamine metabolites in rat cisternal cerebrospinal fluid: major contribution from extrastriatal dopamine neurones

The interpretation of central 3,4-dihydroxyphenylethylamine (dopamine, DA) metabolism, as indicated by determinations in rat cisternal CSF, was investigated using intrastriatal injection of the DA neurotoxin 6-hydroxydopamine (6-OHDA) and intraperitoneal injection of the noradrenergic neurotoxin N-(2-chloroethyl)-N-ethyl-2-bromobenzylamine (DSP4). DA turnover was subsequently determined by measurement of the rate of accumulation of total 3,4-dihydroxyphenylacetic acid and homovanillic acid (DOPAC + HVA) in the CSF after probenecid was given. Two days later the rats were killed, and metabolism of DA and 5-hydroxytryptamine (5-HT) was investigated by determining levels of the amines and their metabolites in brain regions. Although 6-OHDA greatly decreased striatal DA metabolism, this was not paralleled by DA turnover as indicated by CSF, as this fell only moderately and approximately in parallel with results for the brain as a whole. 5-HT metabolism was essentially unaltered. DSP4 considerably depleted noradrenaline and caused smaller decreases of 5-HT metabolism in some regions. However, DA metabolism was not significantly affected, either in brain or CSF, which suggests that noradrenaline neurones make only a small contribution to central DA metabolism. Results as a whole suggest that DOPAC and HVA concentrations in rat cisternal CSF reflect whole brain DA metabolism and derive predominantly from DA neurones in extrastriatal regions of the brain.

Effects of rat ovariectomy on CSF monoamine metabolite levels and elimination

Cerebrospinal fluid (CSF) was removed from the third ventricle of anesthetized male, female, and ovariectomized rats. CSF 3,4-dihydroxyphenylethylamine and serotonin metabolite levels [dihydroxyphenylacetic acid, homovanillic acid (HVA), and 5-hydroxyindoleacetic acid (5-HIAA)] were determined on 15-min samples by liquid chromatography coupled with electrochemical detection. Monoamine oxidase inhibition was used for studying metabolite turnover in the CSF. No difference was observed between male, ovariectomized, and sham-operated female rats. However, ventricular CSF HVA and 5-HIAA levels were significantly higher in the ovariectomized than in the sham-operated rats. These differences do not reflect effects of ovariectomy on brain metabolite production but indicate slower metabolite elimination from the CSF.

Effect of alpha-methyl fluorodopa on dopamine metabolites: importance of conjugation and egress

The effects of D,L-alpha-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.

Determination of brain 5-hydroxytryptamine turnover in freely moving rats using repeated sampling of cerebrovascular fluid

A simple technique is described for repeated sampling of cerebrospinal fluid (CSF) from the freely moving rat and its use in the determinations of 5-hydroxytryptamine (5-HT) turnover validated. A catheter, constructed from polyethylene tubing (PP10) was implanted via a cranial approach into the cisterna magna and x-ray studies confirmed that the catheter avoided the cerebellum. 5-HT turnover was determined from the rate of rise of 5-hydroxyindoleacetic acid (5-HIAA) in both CSF and brain following an injection of probenecid (200 mg/kg i.p.). Concentrations of 5-HIAA, 5-HT and tryptophan were determined by high pressure liquid chromatography. Turnover values for individual rats were obtained using CSF samples. After p-chlorophenylalanine treatment (when brain 5-HT was depleted by 43%) 5-HT turnover values obtained were comparably reduced whether determined from CSF (-67%) or brain (-74%). Thus differences of rat brain 5-HT turnover are proportionately reflected by CSF measurements. The method for sampling of CSF should be applicable in a wide range of pharmacological and physiological situations.

Studies on the accessibility of prolactin and growth hormone to brain: effect of opiate agonists on hormone levels in serial, simultaneous plasma and cerebrospinal fluid samples in the rhesus monkey

The accessibility of prolactin and growth hormone to the cerebrospinal fluid (CSF) was investigated in rhesus monkeys fitted with reservoirs connected to catheters placed in the fourth ventricle. Simultaneous blood and CSF samples were collected after opiate agonists. There was a brisk, marked rise in plasma prolactin following i.v. morphine sulphate which was followed by a slower, lesser rise in CSF prolactin. After i.v. D-Ala2,MePhe4,Met-O-(ol)-enkephalin (DAMME, FK 33-824, Sandoz) two animals responded similarly but the third showed a much smaller plasma and absent CSF response. Growth hormone showed inconsistent plasma patterns after morphine but a late rise following DAMME; however, CSF growth hormone did not change. Infusion of exogenous human prolactin produced plasma and CSF prolactin levels of similar magnitude and time-course as following opiate agonists. Infusions of larger amounts of purified human growth hormone greatly elevated plasma levels but only led to modest increases in CSF growth hormone. It is concluded that prolactin has relatively ready access to CSF, especially in comparison to growth hormone. The possible significance and mechanisms are discussed.

Stereotypy in monkeys and humans

Stereotyped movements are described in monkeys and humans and are classified as arising from constraint, sensory deprivation in infancy, amphetamine treatment or psychotic states. It is argued that, with the exception of cage stereotypies, stereotyped behaviour is evidence of abnormality in the nervous system consequent upon distorted maturational processes, organic defect or biochemical disturbance. Stereotypy is associated with a state of cognitive inflexibility and social and sensory isolation in humans and monkeys. It is suggested that, while no simple biochemical disturbance in the brain can describe these various occurrences of stereotypy, the cross-species occurrence of a syndrome of isolation, cognitive inflexibility and stereotypy implies a related mechanism mediating these divergent effects. If stereotypy is regarded as a consequence of failure to use sensory input to direct behaviour, therapeutic regimes designed to stimulate responsive behaviours and social interactions are more likely to be effective in the long run than direct attempts to suppress stereotypy.

Effect of chronic amphetamine administration on central dopaminergic mechanisms in the vervet

A biochemical study of central dopaminergic mechanisms was carried out in brain tissue from vervet monkeys who had been subjected to chronic amphetamine administration. The brain concentrations of dopamine (DA) and 3,4-dihydroxyphenylacetic acid (DOPAC) were markedly reduced. Significant reductions were also observed in the activities of dopa-decarboxylase (DDC) and tyrosine hydroxylase (TH). A kinetic study of TH revealed a 60% reduction in maximum reaction velocity, consistent with destruction of DA neurones. However, homovanillic acid (HVA) concentrations were only moderately reduced, suggesting a nearly normal production of DA. Hence despite the large depletions in DA concentrations, high affinity binding of 3H-spiperone binding to striatal DA receptors was no different from controls. The results are discussed in relation to the amphetamine psychosis in humans.