Nicholas J. Giarman

Natural occurrence of gamma-hydroxybutyrate in mammalian brain

Abstract Gas chromatographic analysis of bovine, cat, rat and guinea pig brain extracts revealed the presence of a compound with properties identical to those of γ-hydroxybutyrate. A new specific and relatively simple technique involving isotope dilution and gas chromatography is described for the estimation of brain concentrations of γ-hydroxybutyrate. With this technique the endogenous concentration of γ-hydroxybutyrate found in rat brain is 1·78 ± 0·10 nmoles/g while the level found in guinea pig brain is about twice as high (4·10 ± 0·28 nmoles/g).

γ-Butyrolactone and γ-hydroxybutyric acid—I: Distribution and metabolism☆

Abstract Some aspects of the distribution and metabolism of the central nervous system depressants, γ-butyrolactone and γ-hydroxybutyric acid, have been investigated. After the administration of a depressant dose of γ-hydroxybutyrate to the cat, there was a relatively higher concentration of γ-hydroxybutyrate in the cerebellum and in the lower temporal lobe of the cortex than in other areas of the brain examined. The γ-butyrolactone was found to concentrate more in lean muscle than γ-hydroxybutyrate, while there was no difference in the amount of each that appeared in the body fat. The latter finding is explained by the presence of a rapidly acting lactonase in blood and liver that catalyzes the hydrolysis of γ-butyrolactone to γ-hydroxybutyrate. 14 C-carboxyl-labeled γ-hydroxybutyrate and γ-butyrolactone were found to be metabolized very rapidly to 14 CO 2 in the intact rat; both the brain and liver carry out this decarboxylation in vitro . The major pathway of metabolism does not appear to involve formation of succinic acid. These results are related to the nature of the pharmacologically active compound and its duration of action.

DIFFERENTIAL ESTIMATION OF GAMMA-BUTYROLACTONE AND GAMMA-HYDROXYBUTYRIC ACID IN RAT BLOOD AND BRAIN.

A sensitive and specific gas chromatographic technique for estimating concentrations of the anesthetic adjuvants, γ-butyrolactone and γ-hydroxybutyrate, in tissues has been developed. These substances do not appear to occur endogenously in either the blood or the brain of common laboratory animals. The onset and duration of anesthesia caused by the administration of either compound is correlated with the concentration of γ-hydroxybutyrate in the brain, rather than with that of the corresponding lactone.

Evidence that central nervous system depression by 1,4-butanediol is mediated through a metabolite, gamma-hydroxybutyrate

Abstract Gas chromatographic analysis of blood and brain extracts from rats anesthetized with 1,4-butanediol (BD) revealed that BD was metabolized to γ-hydroxybutyrate (GHB), since the latter compound was found in both blood and brain. Further, there appeared to be a correlation between the brain concentration of GHB and the “sleep” induced by BD. (β-hydroxybutyrate, a known antagonist of GHB-induced “sleep” was found also to antagonize BD-induced “sleep” as well as to cause a reduction in the brain concentration of GHB. This evidence is taken to support the view that GHB is the active metabolite involved in the production of the “sleep” induced by BD.

A Mehanism of the Indole Defect in Experimental Phenylketonuria

Rats made phenylketonuric by a diet containing high levels of either phenylalanine alone, or phenylalanine and tyrosine, show a marked reduction in total cerebral stores of serotonin. Evidence from studies both in vitro and in vivo indicates that an important mechanism of this impairment in the metabolism of serotonin is the inhibition by high levels of these amino acids of the active transport of the precursor of serotonin, 5-hydroxytryptophan, into brain.

Drug-induced alterations in the sub-cellular distribution of 5-hydroxytryptamine in rat's brain

Abstract High-speed centrifugation of preparations of brain (rat) has permitted the separation of two forms of 5-hydroxytryptamine (5-HT; serotonin), “bound” and “free”, and the influence of drugs on these forms has been studied. Normally, about 30 per cent of the total endogenous 5-HT is found in the free form. Some drugs known to depress or tranquilize (such as reserpine, chlorpromazine, phenobarbital), irrespective of their effect on total cerebral 5-HT, produce significant increases in the proportion of free 5-HT. The hallucinogenic agent, LSD-25, and the anti-depressant drugs imipramine and β-phenyl iso propylhydrazine lead to an elevation in total 5-HT, which may be accounted for by greater increases in bound than free 5-HT. The anti-depressant drug, iproniazid, produces a rise in both forms of the amine with no significant change in distribution. Among the anti-depressants, only iproniazid completely prevents the release of granule-bound 5-HT which ordinarily is induced by reserpine. This action is not entirely related to inhibition of monoamine oxidase or to the high levels of 5-HT produced by iproniazid.

5-Hydroxytryptamine in Single Neoplastic Mast Cells: A Microscopic Spectrofluorometric Study

5-Hydroxytryptamine, catecholamines, and histamine in mast cells can be distinguished by fluorescence microscopy. Microscopic spectrofluorometry can be used to estimate 5-hydroxytryptamine in single neoplastic mast cells grown in vitro, and to study the effect of reserpine on these cells.

Drug-induced Changes in the Subcellular Distribution of Serotonin in Rat Brain with Special Reference to the Action of Reserpine

Publisher Summary The mode of action of reserpine (and tetrabenazine) on 5-hydroxytryptamine (5-HT) in the brain is more complex than a simple shift of the amine from a bound to an unbound form. It is felt that other agents, which influence the metabolism of monoamines in the brain, may have multiple sites of action on the subcellular level, and studies of their influence on the subcellular distribution of the amines may reveal similar complexities in their action. It is well known, for example, that α-methyldihydroxyphenylalanine not only inhibits the decarboxylase, but also leads to a release of 5-HT. Certain inhibitors of monoamine not only inhibit that enzyme, but also exert an action on the storage granule, which is manifested in an antagonism to the 5-HT releasing action of reserpine.

The effects of p-Cl-phenylalanine on the content and cellular distribution of 5-HT in the rat pineal gland: Combined biochemical and electron microscopic analyses☆

Abstract The norepinephrine and serotonin content of the rat pineal has been examined after treatment with p -Cl-phenylalanine. Within 24 hr after injection of this tryptophane hydroxylase inhibitor (325 mg/kg), the serotonin becomes greatly depleted with recovery occuring over the next 4–6 days; there is no decrease in pineal norepinephrine at the time of the greatest loss of serotonin. Electron microscopically, these monoamine changes are accompanied by a loss of synaptic vesicle electron-opacity within intrapineal axons after fixation in glutaraldehyde and osmium tetroxide. However, there is no apparent change in pineal axonal synaptic vesicle appearance after p -Cl-phenylalanine treatment when the tissue is fixed with KMnO 4 . Since both autoradiographic and scintillation counting estimates of the amount of retained catecholamine with each fixative are quite similar, these differences may reflect the cytochemical reactivity of the vesicle matrix in addition to the vesicle content of monoamine. In any case, these results support the intravesicular storage of serotonin in intrapineal sympathetic axons.

Blood 5-hydroxytryptamine (serotonin) levels after reserpine and electroshock therapy.

Summary Blood 5-HT fell to non-detectable levels after administration of reserpine to patients during a 3 week period. Three weeks after withdrawal of the drug, 5-HT levels had risen but had not yet reached normal values. Electro-shock therapy did not alter the levels of 5-HT in the blood.