Histamine and serotonin metabolism following massive small bowel resection

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Chlorpromazine and dopamine: conformational similarities that correlate with the antischizophrenic activity of phenothiazine drugs

Phenothiazines and butyrophenones are known to alter dopamine (3,4-dihydroxyphenethylamine) metabolism in the brain in a fashion suggesting that they may block dopamine receptors. We observed, using Dreiding molecular models, that dopamine in its solid-state conformation is superimposable upon a portion of the known x-ray structure of chlorpromazine [2-chloro-10-(3-dimethylaminopropyl)-phenothiazine]. The ability of phenothiazine drugs to mimic the dopamine-like conformation correlates with their antischizophrenic efficacy. These structure-activity relationships explain the importance of a substituent in ring a, a three-carbon side chain bearing the amino group, and a hetero atom between rings a and c.

Nuclear localization of histamine in neonatal rat brain

The concentration of histamine in the brains of neonatal rats is considerably higher than that in adults. Subcellular fractionation studies revealed that about 90 percent of the histamine content of neonatal rat brain is confined to the crude nuclear fraction obtained by differential fractionation. Purified nuclei prepared from these fractions retained 90 percent of their histamine content. The nuclear localization of histamine in the brains of neonatal rats suggests a function for histamine in modulating the growth processes of the neonatal brain.

Brain histamine: rapid apparent turnover altered by restraint and cold stress

Histamine content of rat brain was lowered quickly by inhibitors of histidine decarboxylase, suggesting that a portion of brain histamine turns over rapidly. Restraint and exposure to cold also reduced brain histamine levels and markedly augmented its formation in the hypothalamus.

A unique synaptosomal fraction, which accumulates glutamic and aspartic acids, in brain tissue

Subcellular fractionation of rat cerebral cortical slices on sucrose density gradients provides evidence for the existence of a unique synaptosomal fraction (enriched in pinched-off nerve endings) that selectively accumulates glutamic and aspartic acids. The particles in this fraction sediment to a less dense portion of sucrose gradients than do particles that accumulate aromatic, basic, and neutral (large and small) amino acids. Particles that store gamma-aminobutyric acid are even less dense than those that contain exogenous glutamic and aspartic acids. The distribution of endogenous glutamic acid encompasses both that of exogenous glutamic acid and that of the neutral and basic amino acids. These findings provide neurochemical support for the suggestion that glutamic and/or aspartic acid has a specialized synaptic function, perhaps as a neurotransmitter, in the mammalian brain.

Neurotransmitter-specific synaptosomes in rat corpus striatum: morphological variations

This communication describes ultrastructural variations among synaptosomal fractions isolated from the corpus striatum of the rat by incomplete equilibrium sedimentation in sucrose density gradients, and attempts to relate the variations to neurotransmitter-specific synaptosomes. The concentration of synaptosomes in each fraction of the density gradient was found to be correlated with the concentration of potassium, a marker for cytoplasm occluded within synaptosomes. Monoamine oxidase activity was found to be correlated with the incidence of free mitochondria in the gradients. Synaptosomes from denser gradient fractions showed a markedly increased frequency of adherent postsynaptic elements and intraterminal mitochondria. These denser gradient fractions were rich in synaptosomes containing norepinephrine, dopamine, serotonin, and acetylcholine, while synaptosomes in lighter portions of the gradients were rich in gamma-aminobutyric acid and other amino acids. These data suggest that significant morphological variations may exist among different neurotransmitter-specific nerve terminals in the brain.

Amphetamine: differentiation by d and l isomers of behavior involving brain norepinephrine or dopamine

d-Amphetamine is markedly more potent an inhibitor of catecholamine uptake by norepinephrine neurons in the brain than is 1-amphetamine, whereas the two isomers are equally active in inhibiting catecholamine uptake by the dopamine neurons of the corpus striatum. In behavioral studies, d-amphetamine is ten times as potent as 1-amphetamine in enhancing locomotor activity, while it is only twice as potent in eliciting a compulsive gnawing syndrome. This suggests that the locomotor stimulation induced by amphetamine involves central norepinephrine, while dopamine neurons play an important role in the induced compulsive gnawing behavior. Assessment of differential actions of d- and 1-amphetamine may be an efficient method to differentiate behaviors involving norepinephrine or dopamine in the brain.

Antiparkinsonian drugs: inhibition of dopamine uptake in the corpus striatum as a possible mechanism of action

A variety of antiparkinsonian drugs are potent, noncompetitive inhibitors of dopamine uptake into synaptosomes in homogenates of rat corpus striatum. Inhibition of dopamine uptake may potentiate the synaptic actions of dopamine in the striatum and could explain the antiparkinsonian effects of these drugs. This hypothesis accounts for several clinical features of Parkinson's disease and predicts compounds which may be new therapeutic agents.