Catechols in post-mortem brain of patients with Parkinson disease.

BACKGROUND: Dihydroxyphenylacetaldehyde (DOPAL), a cytotoxic metabolite of dopamine, is the focus of the 'catecholaldehyde hypothesis' about the pathogenesis of Parkinson disease. This study explored whether DOPAL is detectable in human striatum - especially in the putamen (Pu), the main site of dopamine depletion in Parkinson disease - and is related to other neurochemical indices of catecholamine stores and metabolism in Parkinson disease. METHODS: Putamen, caudate (Cd), and frontal cortex (Ctx) catechols were measured in tissue from patients with pathologically proven end-stage Parkinson disease (N=15) and control subjects (N=14) of similar age with similar post-mortem intervals. RESULTS: Putamen DOPAL (3% of dopamine in controls) correlated with dopamine and dihydroxyphenylacetic acid both across all subjects and within the Parkinson disease and control groups. Pu dopamine was decreased by 93% and dihydroxyphenylacetic acid 95% in Parkinson disease vs. controls, with smaller decreases of DOPAL (83%) and norepinephrine (73%) in Pu and of dopamine (74%) and dihydroxyphenylacetic acid (82%) in Cd. In Parkinson disease, Pu DOPAL:dihydroxyphenylacetic acid averaged 3.4 times and DOPAL:dopamine 4.4 times control (P=0.03 each). The main catecholamine in Ctx was norepinephrine, which was decreased by 51% in Parkinson disease patients. CONCLUSIONS: Correlated decreases of DOPAL, dopamine, and dihydroxyphenylacetic acid in Parkinson disease reflect severe loss of Pu dopamine stores, which seems more extensive than loss of Pu norepinephrine or Cd dopamine stores. Increased Pu DOPAL:dihydroxyphenylacetic acid ratios in Parkinson disease suggest decreased detoxification of DOPAL by aldehyde dehydrogenase. Elevated levels of cytosolic DOPAL might contribute to loss of dopaminergic neurons in Parkinson disease.

Tritiated norepinephrine: release from brain slices by electrical stimulation.

Slices of rat brain and heart that had concentrated H(3)-norepinephrine were superfused and electrically stimulated. Stimulation induced a marked release of H(3)-norepinephrine with a threshold and a maximum repsonse. Release also occurred with increased concentrations of potassium, presumably due to neuronal depolarization. Inhibition of electrically induced release occurred with low calcium and with chlorpromazine and pentobarbital.

Dopamine receptor binding is increased in diabetic rats.

The binding of [3H]spiperone, a dopamine receptor ligand, to striatal membranes was increased 30 to 35 percent in rats made diabetic with alloxan or streptozotocin. Binding of [3H]spiperone was normal in rats made diabetic with alloxan but treated with insulin. Thus the number of dopamine receptors and central dopaminergic transmission may be altered in diabetes.

Delta-9-tetrahydrocannabinol: metabolism and disposition in long-term marihuana smokers.

Radioactively labeled delta-9-tetrahydrocannabinol (delta(9)THC) administered intravenously to chronic marihuana smokers disappeared from the blood plasma with a half-life of 28 hours as compared to 57 hours for nonusers of marihuana. Apparent volumes of distribution did not significantly differ between the two groups. Within 10 minutes after administration of delta(9)THC, 11-hydroxy-delta(9)THC is present in the plasma of nonusers and chronic users. This metabolite was also present in urine and feces of nonusers and long-term marihuana smokers. In addition, polar metabolites were excreted in urine and feces of both groups for more than 1 week.

Marihuana: studies on the disposition and metabolism of delta-9-tetrahydrocannabinol in man.

Delta(9)-Tetrahydrocannabinol (the major active component of marihuana) administered intravenously to normal human volunteers persists in plasma for more than 3 days (t(1/2) = 56 hours). Its metabolites appear in plasma within 10 minutes after administration and persist along with the precursor compound. Delta(9)-Tetrahydrocannabinol is completely metabolized in man, and the radioactive metabolites are excreted in urine and feces for more than 8 days.

Serotonin release from brain slices by electrical stimulation: regional differences and effect of LSD.

Slices of rat brain which had accumulated tritiated serotonin either in vivo or in vitro were superfused and electrically stimulated. There occurred a marked release of the exogenous amine and, to a lesser extent, its deaminated metabolites, which varied with the region of brain tested and was inhibited by lysergic acid diethylamide.

Evoked release of norepinephrine and serotonin from brain slices: inhibitoon by lithium.

Slices of mammalian brain accumulate H(3)-norepinephrine and H(3)-serotonin when incubated in a physiologic medium containing these tritiated monoamines. When these tissues are subjected to mild electrical stimulation of short duration, which is associated with depolarization of nerve membranes, a striking increase in the rate of efflux of the exogenous labeled monoamines occurs. Stimulation-induced release of both labeled monoamines is diminished by the presence of lithium ions in the perfusing medium; related monovalent cations had no such effect. Evoked release from slices of brain from animals treated intraperitoneally with lithium chloride for 3 days was also reduced.

Proportional release of norepinephrine and dopamine- -hydroxylase from sympathetic nerves.

Dopamine-beta-hydroxylase(DBH), the enzyme that catalyzes the conversion of dopamine to norepinephrine, is localized in the vesicles containing catecholamine in sympathetic nerves. This enzyme is released with norepinephrine when the nerves to the guinea pig vas deferens are stimulated in vitro, and the amount of enzyme discharged increases as the length of stimulation periods increases. The amount of DBH released is proportional to the amount of norepinephrine released, and the ratio of norepinephrine to DBH discharged into the incubation medium is similar to that in the soluble portion of the contents of the synaptic vesicles from the vas deferens. These data are compatible with the release of the neurotransmitter norepinephrine and DBH from symnpathetic nerves by a process of exocytosis.

Delta 9 -tetrahydrocannabinol and ethanol: differential effects on sympathetic activity in differing environmental setting.

Serum dopamine beta-hydroxylase activity, a useful biochemical index of peripheral sympathetic nervous activity, was measured in rats treated with Delta(9)-tetrahydrocannabinol or ethanol or both substances. After 7 days of treatment with either substance, serum dopamine beta-hydroxylase activity decreased significantly. Combined treatment with both agents enhanced the effects of each given alone. In rats subjected to immobilization stress, treatment with Delta(9)- tetrahydrocannabinol appeared to potentiate the stress-induced increase in serum enzyme activity. Treatment with ethanol, with or without Delta(9)-tetrahydrocannabinol, effectively blocked this increase in enzyme activity. These results show that both substances have significant effects on the sympathetic nervous system which are critically influenced by environmental setting.

Dopamine: stimulation-induced release from central neurons.

Dopamine, synthesized in rat brain slices from labeled L-tyrosine or L-dopa, can be released by electrical stimulation of a type known to induce neuronal depolarization. Pretreatment of the animals with 6-hydroxydopamine, which destroys central catecholamine-containing nerve terminals, substantially reduced the release of dopamine synthesized from [(14)C]tyrosine or from a low concentration of [(3)H]dopa, whereas the release of dopamine formed from a high concentration of [(3)H]dopa remained essentially unchanged. The observations that at high concentrations L-dopa may enter noncatecholaminergic cells, undergo decarboxylation to dopamine, and subsequently be liberated in response to depolarization suggest that dopamine may act as a substitute central transmitter, possibly in serotonergic neurons. This mechanism may contribute to L-dopa's clinical effects in parkinsonian patients.

Rat fighting behavior: serum dopamine- -hydroxylase and hypothalamic tyrosine hydroxylase.

Male Sprague-Dawley rats were subjected to 4 weeks of daily periods of immobilization stress. One of two experimental groups was allowed 1 month of recovery. After 4 weeks of stress, there was a significant increase in shockinduced fighting, in the activity of serum dopamine-beta-hydroxylase, and in the activity of hypothalamic tyrosine hydroxylase. The concentration of hypothalamic norepinephrine was not decreased. After 4 weeks of recovery, only serum dopamine-betahydroxylase activity returned to normal; it therefore appears that longterm stress may increase central catecholamine synthesis. possibly resulting in a persistent increase in aggressive behavior.

L-Dopa-induced release of cerebral monoamines.

L-Dopa markedly increased the efflux of tritiated dopamine and tritiated serotonin from rat brain slices. This action appeared contingent on the decarboxylation of L-dopa to dopamine, since it could be blocked by an inhibitor of L-amino acid decarboxylase. Selective destruction of catecholamine-containing nerve terminals by 6-hydroxydopamine significantly decreased the uptake and release of tritiated dopamine but not that of tritiated serotonin. These observations support the hypothesis that a portion of exogenously administered L-dopa may enter central serotonin terminals and undergo decarboxylation to the amine with resultant displacement of the endogenous indoleamine from vesicular stores.

Relation between plasma and cerebrospinal fluid levels of 3-methoxy-4-hydroxyphenylglycol.

Concentrations of free 3-methoxy-4-hydroxyphenylglycol in the plasma and cerebrospinal fluid are highly correlated, but concentrations in the cerebrospinal fluid are always higher than those in plasma, even when large amounts of the catecholamine metabolite are derived from a tumor of the adrenal medulla. This is explained by considering the plasma and cerebrospinal fluid as a two-compartment system in which the rate constants for entry into and exit from the cerebrospinal fluid compartment are similar. 3-Methoxy-4-hydroxyphenylglycol that is synthesized, but not catabolized, in the central nervous system maintains cerebrospinal fluid levels at an increment over those in plasma. This increment can be used to provide the best available index of formation of 3-methoxy-4-hydroxyphenylglycol in the central nervous system.

Schizophrenia: elevated cerebrospinal fluid norepinephrine.

Concentrations of norepinephrine in cerebrospinal fluid are higher in schizophrenic patients, particularly in those with paranoid features, than in normal volunteer subjects of the same age. This observation supports recent reports of elevated concentrations of norepinephrine in specific brain areas adjacent to the cerebral ventricles of paranoid schizophrenic patients. Overflow of the amine from periventricular regions into the cerebrospinal fluid may reflect abnormally high release or diminished enzymatic destruction of norepinephrine in patients with schizophrenia.

Modification of the cardiovascular effects of L-dopa by decarboxylase inhibitors.

Intravenously infused L-dopa (0.3 mg/kg per min) produced hypertension and cardiac arrhythmias in halothane anesthetized dogs. Biochemical studies showed that the heart, kidney, and brain of these animals accumulated significant amounts of catecholamines formed from the administered precursor. Pretreatment of dogs with an extracerebral inhibitor of dopa decarboxylase [D,L-alpha-hydrazino-alpha-methyl-beta-(3.4-dihydroxyphenyl) propionic acid] prevented the development of hypertension and arrhythmias with infusion of L-dopa. Instead, these animals developed significant hypotension. The heart and kidney of these animals accumulated markedly reduced amounts of catecholamines formed from L-dopa compared with dogs receiving L-dopa alone: the amount of catecholamines accumulated in brain was unchanged. L-dopa, after extracerebral decarboxylase inhibition, appeared to produce hypotension by reducing peripheral vascular resistance without altering sympathetic nerve function. During hypotension, cardiac output was not altered and arterial pressure in perfused hindlimbs fell, even though flow was maintained. The pressor response to intravenous injections of norepinephrine and dopamine was unchanged. Hindlimb arterial pressure response to direct electrical stimulation of the lumbar sympathetic trunk was also unchanged. Pretreatment with a drug which inhibits brain as well as extracerebral dopa decarboxylase [D,L-seryl-2,3,4-trihydroxybenzylhydrazine hydrochloride] abolished all effects of L-dopa on blood pressure. In these animals, there was a marked reduction of catecholamine formation from L-dopa in the brain as well as the heart and kidney. It appears that L-dopa produces opposite effects on blood pressure depending on the site of accumulation of its metabolic products, dopamine and norepinephrine. If L-dopa is rapidly decarboxylated to catecholamines in peripheral organs, hypertension and cardiac arrhythmias occur. If peripheral dopa decarboxylase is selectively inhibited, a centrally mediated hypotensive effect, probably secondary to the accumulation of catecholamines in the brain, becomes apparent. If dopa decarboxylase is inhibited in the brain in addition to extracerebral organs, L-dopa has no effect on blood pressure.

Plasma dihydroxyphenylglycol and the intraneuronal disposition of norepinephrine in humans.

We examined plasma levels of the sympathetic neurotransmitter norepinephrine (NE) and its deaminated metabolite dihydroxyphenylglycol (DHPG) during supine rest in healthy human subjects and in sympathectomized patients, during physiological (tilt) or pharmacological (yohimbine, clonidine) manipulations known to affect sympathetically mediated NE release, during blockade of neuronal uptake of NE (uptake-1) using desipramine, and during intravenous infusion of NE. Healthy subjects had a mean arteriovenous increment in plasma DHPG in the arm (10%, P less than 0.05), whereas sympathectomized patients had a mean arteriovenous decrement in DHPG in the affected limb (mean decrease 21%, P less than 0.05 compared with healthy subjects). Tilt and yohimbine, which stimulate, and clonidine, which inhibits, release of endogenous NE, produced highly correlated changes in plasma NE and DHPG (r = 0.94). Pretreatment with desipramine abolished DHPG responses to yohimbine while enhancing NE responses. To attain a given increase in plasma DHPG, about a tenfold larger increment in arterial NE was required during NE infusion than during release of endogenous NE. When plasma NE was markedly suppressed after administration of clonidine, plasma DHPG decreased to a plateau level of 700-800 pg/ml. The results indicate that (i) plasma DHPG in humans is derived mainly from sympathetic nerves; (ii) increments in plasma DHPG during stimulation of NE release result from uptake of NE into sympathetic nerve endings and subsequent intraneuronal conversion to DHPG; (iii) plasma DHPG under basal conditions probably is determined mainly by net leakage of NE into the axonal cytoplasm from storage vesicles; and (iv) increments in NE concentrations at neuronal uptake sites can be estimated by simultaneous measurements of DHPG and NE during NE infusion and NE release. Measurement of NE and DHPG provides unique clinical information about sympathetic function.

Measurement of regional neuronal removal of norepinephrine in man.

We describe here and validate an in vivo technique to measure the regional proportionate removal of norepinephrine (NE) by neuronal uptake (Uptake1) in man. The measurement is based on the steady-state arterial and venous concentrations of tritiated NE and tritiated isoproterenol (ISO) during simultaneous infusion of both. The validity of this technique depends on the removal of circulating NE, but not of ISO, by sympathetic nerve endings and on there being no other factor contributing to the net difference in the plasma disappearance of these catecholamines. To test these hypotheses, we compared the removal of NE in the arm with that of ISO in 14 people and the effects of pretreatment with the specific inhibitor of Uptake1, desipramine, in 8 people. In all the subjects a greater percent of NE than of ISO was removed during passage of blood through the forearm (54 vs. 46%, P less than 0.0001). Pretreatment with desipramine decreased significantly the removal of NE to virtually exactly that of ISO. The difference in NE and ISO clearances by arm tissues was therefore completely accounted for by Uptake1. About 15% of infused NE which is removed in the arm is removed by Uptake1. The ability to measure regional Uptake1 should contribute to better understanding of the relationship between circulating levels of plasma NE and sympathetic neural activity and may allow detection of abnormalities of neuronal norepinephrine removal in clinical disease states.

Plasma l-[3H]norepinephrine, d-[14C]norepinephrine, and d,l-[3H]isoproterenol kinetics in essential hypertension.

We infused tracer-labeled l-[3H]-norepinephrine, d-[14C]norepinephrine, and d,l-[3H]-isoproterenol simultaneously into patients with essential hypertension and into normotensive control subjects, in order to determine whether abnormalities in the disappearance kinetics of these substances characterized the hypertensive patients. The mean preinfusion venous plasma norepinephrine concentration was somewhat higher in the hypertensive group (260 vs. 194 pg/ml, P = 0.06), but the groups did not differ in the disappearance kinetics of l- or d-norepinephrine or of isoproterenol. Preinfusion plasma norepinephrine was significantly positively correlated with calculated spillover rates in both the hypertensive and normotensive groups, but not with norepinephrine clearances. The d/l ratio in plasma norepinephrine was the same as in the infusate during and after the infusion, even after pretreatment with the neuronal norepinephrine uptake blocker, desipramine. Because isoproterenol is not taken up by nerve endings, the ratio of [3H]isoproterenol to l-[3H]norepinephrine increased after the infusion ended. This increase was almost completely abolished by pretreatment with desipramine. These results indicate that (a) increased plasma norepinephrine levels seen in some patients with essential hypertension result from increased sympathetic neural activity and not from decreased clearance of norepinephrine, (b) changes in the isoproterenol/norepinephrine ratio after simultaneous infusion of both provide an index of neuronal norepinephrine uptake in man, and (c) neuronal norepinephrine uptake is not stereospecific.

Decreased stress responsivity of central and peripheral catecholaminergic systems in aged 344/N Fischer rats.

We investigated the effects of stress on central and peripheral sympatho-adrenal and sympatho-neural functions in healthy, intact young (3-4 mo) and aged (24 mo) male Fischer 344/N rats. Extracellular fluid (ECF) levels of the catecholamines norepinephrine (NE), dihydroxyphenylglycol (DHPG), methoxyhydroxyphenylglycol (MHPG), and dihydroxyphenylacetic acid (DOPAC) were obtained by microdialysis in the paraventricular nucleus (PVN) of the hypothalamus at baseline and during immobilization (IMMO). The baseline levels of these substances were similar in both age groups, and their concentrations increased significantly in response to IMMO. The IMMO-induced increases of NE and MHPG, however, were significantly smaller in old than in young rats. Plasma levels of the catecholamines NE, DHPG, MHPG, DOPAC, dihydroxyphenylalanine (DOPA), epinephrine (EPI), dopamine (DA), and HVA were also determined in young and old rats during IMMO. Basal levels of these substances were significantly higher in old than in young rats. The magnitude of the IMMO-induced increases in the majority of these compounds however, was significantly smaller in old than in young rats. We conclude that, at the basal state, aging in the Fischer rat is associated with normal PVN ECF, but high plasma catecholamine levels; at stress state, however, old rats have substantially lesser activation of their central and peripheral catecholaminergic systems than young rats.

Specific genetic deficiencies of the A and B isoenzymes of monoamine oxidase are characterized by distinct neurochemical and clinical phenotypes.

Monoamine oxidase (MAO) exists as two isoenzymes and plays a central role in the metabolism of monoamine neurotransmitters. In this study we compared the neurochemical phenotypes of previously described subjects with genetically determined selective lack of MAO-A or a lack of both MAO-A and MAO-B with those of two subjects with a previously described X chromosome microdeletion in whom we now demonstrate selective MAO-B deficiency. Mapping of the distal deletion breakpoint demonstrates its location in intron 5 of the MAO-B gene, with the deletion extending proximally into the Norrie disease gene. In contrast to the borderline mental retardation and abnormal behavioral phenotype in subjects with selective MAO-A deficiency and the severe mental retardation in patients with combined MAO-A/MAO-B deficiency and Norrie disease, the MAO-B-deficient subjects exhibit neither abnormal behavior nor mental retardation. Distinct neurochemical profiles characterize the three groups of MAO-deficient patients. In MAO-A-deficient subjects, there is a marked decrease in deaminated catecholamine metabolites and a concomitant marked elevation of O-methylated amine metabolites. These neurochemical changes are only slightly exaggerated in patients with combined lack of MAO-A and MAO-B. In contrast, the only biochemical abnormalities detected in subjects with the MAO-B gene deletion are a complete absence of platelet MAO-B activity and an increased urinary excretion of phenylethylamine. The differences in neurochemical profiles indicate that, under normal conditions, MAO-A is considerably more important than MAO-B in the metabolism of biogenic amines, a factor likely to contribute to the different clinical phenotypes.