The psychological effects of dopamine-beta-hydroxylase inhibition in normal subjects

Acute administration of the dopamine-beta-hydroxylase (DBH) inhibitor, fusaric acid, combined with L-dopa, 500 mg, produced discernible psychological abnormalities in normal subjects. These were not found after L-dopa alone, or after placebo. The changes, lasting a few hours, were manifested by significant increases in "total psychopathology," and in a number of subscales on the Brief Psychiatric Rating Scale. Changes were also found in mood ratings on adjective checklists, and inkblot tests. A variety of effects were found on psychiatric interview. Since DBH does not occur in dopamine neurons, it is likely that the psychological effects were due to changes in dopamine or norepinephrine in norepinephrine neurons.

Effect of an inhibitor of dopamin-beta-hydroxylase on the acquistion and retention of four different avoidance tasks in mice

The effect of [bis-(4-methyl-1-homopiperazinylthiocarbonyl)-disulfide] (FLA-63) (40 mg/kg, i.p.) on acquisition and retention in four different avoidance tasks was evaluated in mice. In all tasks animals were submitted to a training session on one day and to a retest session 24 h later. The drug or its vehicle were given either 2 h prior to training and/or retest (pretrial treatments) or immediately after the end of the training session (posttrial treatments). Two hours after injection, FLA-63 was found to lower brain norepinephrine (NE) levels by 51% without affecting those of dopamine (DA). Pretrial administration of the drug resulted in poorer performance of step-through and step-down passive avoidance as well as of step-up active avoidance in retest sessions. There was no apparent posttrial effect of the drug nor any effect on acquisition in these tasks. The drug was without influence on either acquisition or retention in an any-way passive avoidance task in which the response required from the animals was immobility. No evidence for state-dependent learning was detected in any of the tasks. The data are consistent with the hypothesis of an involvement of NE either in memory processes or in events parallel and related to memory processes. The present results rule out, however, several such possible parallel events (effects on acquisition, motor disturbances, and effects on reactivity to shocks).

Noradrenergic transmission and female sexual behavior of guinea pigs

Treatment with the dopamine beta-hydroxylase (DBH) inhibitor U-14,624 (50, 100, or 150 mg/kg) blocked the induction of lordosis behavior be estradiol benzoate (EB) and progesterone (P) in ovariectomized guinea pigs. After treatment with U-14,624 (100 mg/kg), norepinephrine (NE) content of medial basal hypothalamus, preoptic area and cortex was reduced (by 55%) and dopamine (DA) content of medial basal hypothalamus was increased (by 155%) during the period when females treated with EB and P normally display lordosis. Treatment with the NE receptor stimulator clonidine (1.0 mg/kg) restored lordosis behavior in females treated with EB, P, and U-14,624 (100 mg/kg), but the putative DA and serotonin (5-HT) receptor blockers pimozide (1.0 mg/kg) and methysergide (20.0 mg/kg) were ineffective in this respect. Thus, inhibition of lordosis after treatment with U-14,624 appeared to be attributable primarily to a reduction in NE neurotransmission, rather than to increase in DA or 5-HT activity. Because clonidine induced lordosis in females treated with EB, P, and U-14,624, it seemed unlikely that the facilitatory effects of clonidine on lordosis were mediated by activation of presynaptic alpha-adrenergic receptors (i.e. inhibitory NE autoreceptors) rather than by postsynaptic alpha-receptors. In addition, pretreatment with the postsynaptic alpha-adrenergic antagonist phenoxybenzamine (20.0 mg/kg) blocked the facilitation of lordosis by clonidine (1.0 mg/kg) in females primed with EB alone and with EB plus P. Thus, the facilitatory effects of clonidine on lordosis appear to be mediated by activation of postsynaptic alpha-adrenergic (i.e. NE) receptors. The results of this study provide further evidence that NE neurotransmission facilitates the expression of female sexual behavior in guinea pigs.

Central dopamine receptors regulate blood eosinophilia in the rat

Dopaminergic agents, dopa and apomorphine, affected biphasically the blood eosinophil count in the rat: low doses of the drug elevated, while high doses lowered it. The response to a high dose of dopa was retained in rats pretreated with an inhibitor of dopamine-beta-hydroxylase, U 10, 157, but prevented by a centrally acting dopa decarboxylase inhibitor, NSD 1015. This indicates that the eosinopenia observed after large doses of dopa is due to the action of dopamine formed from the precursor. As intracerebroventricular injections of Ldopa also produce eosinopenia, the central site of dopamine action is indicated. The eosinopenic response to apomorphine was antagonized by a dopamine receptor blocking agent, haloperidol. This indicates that some central dopamine receptors are involved in the regulation of the eosinophil count in circulating blood. The hypophysis seems to play a crucial role in the phenomenon observed, as no eosinopenia was produced by dopa in hypophysectomized rats.

Enhancement of dopamine-induced stimulation of pancreatic secretion by 5-dimethyldithiocarbamylpicolinic acid (YP-279), a dopamine beta-hydroxylase inhibitor

Effect of 5-dimethyldithiocarbamylpicolinic acid (YP-279), a dopamine beta-hydroxylase inhibitor, on the secretion of pancreatic juice induced by dopamine was investigated in preparations of the isolated blood-perfused canine pancreas. Either a single injection (300 micrograms) or an infusion (100 micrograms/min) of YP-279 intra-arterially (i.a.) caused no change in the outflow of the pancreatic juice, but the secretagogue effect of dopamine (1-10 micrograms, i.a.) was enhanced by the infusion of YP-279 (100 micrograms/min, i.a.) for 60 min. The previous conclusion obtained with fusaric acid was confirmed as follows; the dopamine beta-hydroxylase activity controls the dopaminergic mechanism of the pancreatic secretion.

The enzyme-bound copper of dopamine beta-monooxygenase. Reaction with copper chelators, preparation of the apoprotein, and kinetics of the reconstitution by added copper

The enzyme-bound copper of dopamine beta-monooxygenase reacted rapidly with the chelator bathocuproine disulfonate; the reaction in the presence of ascorbate was completed in 2 min at 25 degrees C with 1mM chelator. This reaction and also the reaction with EDTA could be used to prepare the apoenzyme, which in both cases was completely reactivated in less than 10 s. The reactivation data gave apparent Michaelis constants for copper 0.03 -- 0.2 micron. Trace amounts of copper in buffers and assay mixtures gave significant reactivation without added copper, unless they had been treated with a chelating resin. Titrations using the different chelation rates of free and enzyme-bound copper indicated that four copper atoms are bound per enzyme molecule of four subunits. The native enzyme was more stable against thermal inactivation than the apoenzyme, but this stability was only partially restored by addition of copper to the apoenzyme.

3-Substituted adenines. In vitro enzyme inhibition and antiviral activity

The direct alkylation of adenine at the 3 position has been extended to produce series of 3-alkyl-, 3-allyl-, and 3-(substituted benzyl)adenines. When these compounds were tested for enzyme inhibition and antiviral activity in vitro, 3-n-pentyladenine was found to be the most active compound in inhibiting the enzyme dopamine-beta-hydroxylase, and 3-(2-bromobenzyl)adenine showed the most striking inhibition of multiplication of Vaccinia virus and of Herpes simplex virus in tissue culture.

Accumulation of a tetrahydroisoquinoline in phenylketonuria

3',4'-Deoxynorlaudanosolinecarboxylic acid (DNLCA), a tetrahydroisoquinoline derived from dopamine and phenylpyruvic acid, has been detected by computerized mass fragmentography in urine of phenylketonuric children and in urine and brain of rats with experimentally induced hyperphenylalaninemia. Levels of DNLCA in brain of treated animals were more than tenfold higher than controls, and the excess tetrahydroisoquinoline appeared to accumulate in the cerebellum and cortex. DNLCA is a noncompetitive inhibitor of dopamine beta-hydroxylase (inhibition constant, Ki, = 0.42 mM) and is taken up by the brain.

Circadian changes in adrenal dopamine-beta-hydroxylase activity: dependency of change at darkness onset, and the effect of pinealectomy, on animal strain and age

In a previous study we found a daily darkness- and pineal-dependent rise in adrenal dopamine-beta-hydroxylase (DBH) activity in 4-month-old S1 rats. The present investigation shows that aged (12 to 14-month-old) S1 rats do not have such a change in DBH activity. Similarly in the relatively younger (100-day-old) rats of a different (Holtzman) strain such a change was not found. Also pinealectomy did not seem to have any effect on adrenal DBH in either of these two strains of rats, young or old at times just before and after the onset of darkness. In both S1 and Holtzman rats, the concentration of copper-sensitive endogenous inhibitors of DBH remained unaltered following the surgical extirpation of pineal. Photoperiodic change from light to dark also had no significant effect on the inhibitor content in these two strains of rats. It is concluded that there are age and strain dependencies in the behavior of adrenal DBH activity at the daily onset of darkness.

Role of monoamine neural systems in L-dihydroxyphenylalanine-stimulated activity

The potentiation of the stimulatory response to L-dihydroxyphenylalanine (L-dopa) in 6-hydroxydopamine-treated rats given a peripheral decarboxylase inhibitor occurred only after treatments that destroyed dopamine-containing fibers, Destruction of serotonin- or norepinephrine-containing fibers did not potentiate the action of L-dopa. Furthermore, other data indicated thatL-dopa-induced activity could not be attributed to release of serotonin or to the formation of norepinephrine. That the L-dopa must be converted to catecholamines was demonstrated by antagonism of the activity responses to L-dopa with inhibition of decarboxylases in brain. After destruction of serotonin-containing fibers with 5,7-dihydroxytryptamine, L-dopa-induced activity in 6-hydroxydopamine-treated rats was significantly reduced, as was the accumulation of dopamine formed from L-dopa. These latter data provide direct evidence that serotonergic fibers contribute to the accumulation of dopamine in brain after L-dopa administration to 6-hydroxydopamine-treated rats.

Effects of catecholamine manipulations on three different self-stimulation behaviors

Rats with self-stimulation electrodes in the medial part of lateral hypothalamus (LH) or in the lateral part of LH were trained to bar press, to run in a continuous, square-shaped runway, and to move their tails from side to side while otherwise restrained, all using LH stimulation on an FI 2 sec schedule as the reinforcement. At low doses of pimozide (a dopaminergic blocker) or of FLA-57 (a dopamine beta-hydroxylase inhibitor) different effects on rates of responding were observed on each of the three tasks at the two electrode placements, indicating that the rate reductions were not the results of specific performance effects of the drugs. The patterns of rate changes suggested that the effects of LH stimulation on behavior in the runway were primarily, but not exclusively mediated by a dopaminergic system; that the effects of LH stimulation on tail movement were primarily, but not exclusively mediated by a noradrenergic system; and that the effect of LH stimulation on bar pressing was mediated by both, or either of these substrates. These results suggest that the reinforcement of behavior by LH stimulation is flexibly mediated by at least two different neural systems.

Low serum dopamine beta-hydroxylase activity. A marker of congestive heart failure

To gain information about the nature of disturbances in sympathetic nervous system control in congestive heart failure, serum dopamine beta-hydroxylase (DBH) activity was measured in 30 patients with heart failure of diverse etiologies and 29 healthy normotensive controls. The heart failure patients had been symptomatic for at least 6 wk and had elevated filling pressures, low cardiac indices, low ejection fractions, and wide arteriovenous oxygen differences. DBH activity was 47.1+/-4.7 (mean+/-SE) for the controls and 14.4+/-2.7 IU for the heart failure patients (P < 0.001). Sera from some patients with heart failure had potent inhibitory effects on DBH activity of normal sera. The inhibitor was heat stable and dialyzable and could be demonstrated despite presence of N-ethylmaleimide or Cu(++) in the reaction mixture. However, some inhibitory activity was also present in sera of normal patients; this inhibitory property was not demonstrable in unheated normal serum, but was unmasked when DBH was heat inactivated. It is proposed that although the inhibitor may have been a factor in low serum DBH activity in some patients with heart failure, the major cause of the low activity in the heart failure group was a reduced rate of synthesis or release of the enzyme by sympathetic nerves. This may reflect a dissociation between rates of neural release of norepinephrine and release of DBH in chronic, severe heart failure. The observation of low serum DBH levels in patients with heart failure suggests that measurement of DBH levels may serve as a useful indicator of cardiac dysfunction.

The effects of some dopamine-beta-hydroxylase inhibitors on the control mechanisms of the estrous cycle in rats

Disulfiram (DS) administered in single doses of 200--400 mg/kg i.p. before the critical period of proestrus (9--11 h), or in diestrus--2 (20--23 h), induced in most animals prolongation of the estrus, i.e. an antiovulatory action. FLA-63 had the same effect in a smaller dose (2 mg/kg s.c.) DS elicited the ovulation-blocking action only in doses known to reduce the cerebral noradrenaline level. For the central site of DS action plead its efficacy after i.v.c. administration in a much smaller dose (1 mg/rat), the reduction of the uterine weight, as well as the lack of any significant influence of the drug on the peripheral actions of estradiol. The fact that the two DBH-inhibitors provoked mostly an antiovulatory effect supports the stimulatory role of adrenergic neurons in the control of LRF secretion, because DBH is present only in these neurons and not in the dopaminergic pathways.

Effects of catecholamine manipulations on three different self-stimulation behaviors

Rats with self-stimulation electrodes in the medial part of lateral hypothalamus (LH) or in the lateral part of LH were trained to bar press, to run in a continuous, square-shaped runway, and to move their tails from side to side while otherwise restrained, all using LH stimulation on an FI 2 sec schedule as the reinforcement. At low doses of pimozide (a dopaminergic blocker) or of FLA-57 (a dopamine beta-hydroxylase inhibitor) different effects on rates of responding were observed on each of the 3 tasks at the 2 electrode placements, indicating that the rate reductions were not the results of specific performance effects of the drugs. The patterns of rate changes suggested that the effects of LH stimulation on behavior in the runway were primarily, but not exclusively mediated by a dopaminergic system; that the effects of LH stimulation on tail movement were primarily, but not exclusively mediated by a noradrenergic system; and that the effect of LH stimulation on bar pressing was mediated by both, or either of these substrates. These results suggest that the reinforcement of behavior by LH stimulation is flexibly mediated by at least 2 different neural systems.

Inhibition of dopamine beta-hydroxylase by 4-hydroxypyrazole: ethanol-pyrazole effects on serum dopamine beta-hydroxylase in vivo

Chronic pyrazole treatment caused a 40% decrease in rat serum dopamine beta-hydroxylase (DBH) activity. Ethanol given simultaneously with pyrazole prevented the inhibition. 4-Hydroxypyrazole, the major metabolite of pyrazole, competitively inhibited both rat serum DBH and partially purified bovine adrenal DBH in vitro. In vivo, 4-hydroxypyrazole caused large decreases in rat serum (53-84%) and adrenal (97%) DBH activity but had no effect on brain enzyme. The decrease in rat serum DBH after chronic pyrazole treatment and the pyrazole-induced changes in physiological parameters, such as body weight and temperature, may be due to the formation of 4-hydroxypyrazole.

Difficulties in comparing catecholamine-related enzymes from the brains of schizophrenics and controls

The catecholamine-forming and metabolizing enzyme tyrosine hydroxylase, dopa decarboxylase, dopamine-beta-hydroxylase, phenylethanolamine N-methyltransferase, and catecholamine-O-methyltransferase, as well as the endogenous inhibitor of dopamine-beta-hydroxylase were compared in the brains of schizophrenics and controls. While there were no statistically significant differences in the enzyme or inhibitor activity between groups, tbre was a decided trend toward a decreased enzyme activity in the brains of the schizophrenics. From another set of control brains it was found that changes in human enzyme activity following death are variable and may be dependent on how the brains were handled. Thus, it is unclear whether the apparent differences between schizophrenics and controls were present when they were alive or occurred after death.

Biphasic effect of chlorpromazine on rat paradoxical sleep: a study of dose-related mechanisms

The experiments reported here investigated the effect of chlorpromazine (CPZ) alone or after inhibition of catecholamine (CA) synthesis on paradoxical sleep (PS) in the rat. The dose--response curve for CPZ was biphasic with enhancement of PS after low doses, and depression of PS after higher doses. In contrast, low doses of CPZ after inhibition of CA synthesis markedly decreased PS. This decrease was greater after tyrosine hydroxylase inhibition than after dopamine-beta-hydroxylase inhibition. These results support the view that low doses of CPZ produce increased activity in brain CA synapses, and that both dopamine and noradrenaline participate in the control of PS in the rat.

Suppression of voluntary ingestion of morphine by inhibition of dopamine-beta-hydroxylase

Male Wistar rats were exposed to a free choice between water and a morphine-sucrose solution. Following stabilization of baseline levels of consumption of morphine, the animals were injected for 5 consecutive days with either FLA-57 (45 or 60 mg/kg i.p.), a non-toxic dopamine-beta-hydroxylase inhibitor or its vehicle. The FLA-57 treated animals significantly attenuated their preference for morphine during the injection and post-injection periods although there were no significant differences related to the dosages used. These treatments produced a concomitant reduction in central norepinephrine levels suggesting that norepinephrine may be involved in the mediation of the reinforcing properties of morphine consumed by laboratory rats. The possibility of common neural mechanisms regulating the pharmacological actions of both morphine and ethanol are discussed.