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

Controlled randomized group comparison of nomifensine and imipramine in depressive illness

1. Nomifensine, an isoquinoline dopaminergic agonist, was investigated in a randomized double-blind group comparison with imipramine, in 40 out-patients with depression. 2. Assessments were made at weekly intervals for 4 weeks using the Hamilton Depression Scale and the Beck Depression Inventory. Blood, kidney and liver function were also monitored weekly. 3. Nomifensine was shown to be at least as effective as imipramine in relieving depression and to relieve tha anxiety component of the disease significantly more rapidly. Neither drug produced serious unwanted effects.

Radioautographic study of in vivo incorporation of 3H-monoamines in the cat caudate nucleus: identification of serotoninergic fibers

The localization of radioactivity was examined in the caudate nucleus of the cat, treated with an MAO inhibitor, following local superfusion of the ventricular surface of the structure with low concentration of 3H-catecholamines or [3H]5-HT. The caudate nucleus was superfused continuously from 30 to 240 min using a cup technique. Light microscope or high resolution radioautographs revealed: (1) a rather diffuse incorporation of 3H-catecholamines under the subependymal region which could be hardly attributed to a specific population of nerve terminals. A loose binding of 3H-catecholamines into dopaminergic terminals could be involved in this effect. (2) An intense and selective uptake of [3H]5-HT in fine scarce varicose nerve fibers localized in the ventricle as in the subependymal layer and in the neuropil of the nucleus. The labeled fibers contained numerous round or elongated large granular vesicles of 80-120 nm and exhibited only very few synaptic contacts suggesting a possible extrasynaptic liberation of 5-HT.

Restoration of self-stimulation inhibited by neuroleptics

Pimozide-induced inhibition of lever-pressing for brain stimulation in the lateral hypothalamic area was differentially restored by the centrally acting anticholinergic, dexetimide and by different dopaminergic drugs. In addition, a differential antagonism towards chlorpromazine-induced inhibition of self-stimulation was shown. The results indicate that anticholinergis (non-competitive antagonism) or drugs which enhance endogenous neuro-transmission by increased release or by uptake blockade (competitive antagonism) are able to reserve the neuroleptic-induced inhibition of self-stimulation more effectively than are receptor agonists.

Effect of psychotropic drugs on caudate spindle in cats

To ascertain whether neuroleptics act on the caudate nucleus itself, the effects of these compounds as well as other centrally acting drugs were examined in relation to caudate spindle and EEG arousal responses (sciatic nerve stimulation) in gallamine-immobilized cats. Haloperidol and chlorpromazine enhanced the caudate spindle at a dose which had no effect on the EEG arousal response. On the other hand, clozapine and a higher dose of chlorpromazine enhanced the caudate spindle, but depressed the arousal response. High frequency stimulation of the sciatic nerve suppressed the caudate spindle. Pentobarbital, biperiden and diazepam, while depressing the arousal response, caused an enhancement of the caudate spindle. Imipramine at a low dose had no effect on either response, whereas at a high dose this drug enhanced the caudate spindle with concomitant depression of the arousal response. From these results, it may be concluded that the enhancing action on the caudate spindle induced by haloperidol and a low dose of chlorpromazine is due to an increase in susceptibility of the caudate nucleus itself. In addition, it is suggested that depression of the activating system is involved in an appearance of the caudate spindle.

Time course of nigrostriatal degeneration in parkinson's disease. A detailed study of influential factors in human brain amine analysis

It could be shown that the post mortem analysis of biogenic amines, precursors and metabolites in the human brain are influenced by various parameters. 1. The patient's medical history; long term observations of the course of the disease; age; sex. 2. Terminal illness; duration of terminal illness. 3. Previous treatment with drugs; last drugs. 4. Time interval between last drug treatment and death; time of day and date of last drug consumption. 5. Rapidity of death; time of death; duration of coma. 6. Changes occurring in tissues before death; patients' constitution during terminal illness. 7. Changes in concentration of the biogenic amines, precursors, and metabolites depending on the patient's age. 8. Time between death and necropsy. 9 Dissection of specimen. 10. Period of storage; temperature of storage. 11. Chronbiological rhythm of substances. 12. Methods of assayL 13. Homogeneity of all mentioned parameters in the control group and patient's group. For the first time it could be demonstrated that the time course of nigrostriatal degeneration, independent of the age of the parkinsonian at the beginning of the illness, is linear for the last stage and the denervation progressively increases as the duration of illness progresses.

Methylphenidate-like effects of the new antidepressant drug nomifensine (HOE 984)

Nomifensine (HOE 984) belongs to a chemically new class of drugs with reported antidepressant properties. Nomifensine, like methylphemidate, d-amphetamine and apomorphine, induces strong, intense stereotypes behaviour in the rat. The nomifensine-induced stereotyped behaviour was completely antagonized by pretreatment with reserpine (7.5 mg/kg, 18 h) but not by short-time pretreatment with alpha-methyltyrosine (250 mg/kg, 2 h.) Nomifensine thus differs from d-amphetamine and apomorphine but resembles methylphenidate on stereotyped behaviour. Nominfensine, M1 (8-amino-2-methyl-4-(4-hydroxyphenyl)-1,2,3,4-tetrahydroisoquinoline fumarate) (Hoechst), methylphenidate and d-amphetamine induced a strong increase in the brain level of homovanillec acid (HVA), whereas the dopamine uptake inhibitor benztropine induced no changes in HVA and cocaine induced only a small increase. Nomifensine and the M1 metabolite, like methylphenidate, also increased 3,4-dihydroxyphenylacetic acid (DOPAC) whereas amphetamine, apomorphine, benztropine and cocaine decreased this dopamine metabolite. This suggests that the stereotyped licking and/or biting activities in the rat are related to dopamine releasing properties of nomifensine, methylphenidate and amphetamine. This is further supported by an inverse relationship between the in vitro dopamine uptake inhibitory concentrations and the sterotypy-inducing dose levels of nomifensine and d-amphetamine. Amphetamine caused a strong, and nomifensine and apormorphine a week increase in brain 3-methoxy-4-hydroxyphenylglycol (MOPEG).

Topographical distribution of dopaminergic innervation and of dopaminergic receptors in the rat striatum. I. Mictoestimation of [3H] dopamine uptake and dopamine content in microdiscs

Topographical variations in the uptake of [3H] dopamine (DA) and in the endogenous content of DA were estimated in the striatum of the rat. For this purpose, microdiscs were punched out in serial 500 mum sections. [3H] DA uptake was measured in 0.25 M sucrose homogenates prepared from microdiscs punched out from frozen slices (--7C). This uptake was similar to that observed in fresh tissues. It was unaffected by desmethylimipramine (5 X 10(-7) M), inhibited by benztropine (10(-6) M) and no longer detectable after 6-hydroxydopamine-induced degeneration of the nigrostriatal dopaminergic pathway. Both [3H] DA uptake and DA content decreased regularly from the rostral to the caudal part of the structure. In contrast, no important differences could be found in the dorso-ventral plane. These results suggest that the extent of dopaminergic innervation is heterogenous within the structure.

Central dopaminergic neurons: effects of alterations in impulse flow on the accumulation of dihydroxyphenylacetic acid

Stimulation of the nigro-neostriatal or mesolimbic dopamine pathway results in a stimulus dependent increase in the accumulation of dihydroxyphenylacetic acid (DOPAC) in the neostriatum and olfactory tubercles, respectively. A block of impulse flow induced pharamacologically by administration of gamma-butyrolactone or by placement of a lesion in the dopamine pathway results in a decrease in the steady state levels of DOPAC. Drugs which have previously been shown to alter impulse flow in central dopaminergic neurons also produce a predictable change in the brain levels of DOPAC. Drugs which increase impulse flow in nigro-neostriatal or mesolimbic dopamine neurons increase DOPAC levels in the striatum and olfactory tubercles and drugs which reduce impulse flow cause a reduction in DOPAC. Pargyline, a monoamine oxidase inhibitor, causes a rapid depletion of striatal DOPAC suggesting that this metabolite is rapidly cleared from the brain. Administration of benztropine, a potent inhibitor of dopamine reuptake, causes a significant decrease in striatal DOPAC and partially prevents the stimulus-induced increase in the accumulation of DOPAC. These observations together with the finding that about 85% of the DOPAC in the striatum disappears when the dopamine neurons in the nigro-neostriatal pathway are destroyed suggests that the majority of striatal DOPAC is formed within the dopaminergic neurons and may reflect the metabolism of dopamine which has been released and recaptured. We conclude that short-term changes in brain levels of DOPAC appear to provide a useful index of alterations in the functional activity of central dopaminergic neurons.

Release of 3H-alpha-methyl-m-tyramine from rat striatum in vitro

Release of 3H-d-alpha-methyl-m-tyramine (3H-MMTA), a false dopaminergic transmitter, from rat striatum was studied in vitro. After its initial uptake, 3H-MMTA was released by high K+ and by amphetamine. The release requirements were essentially the same as those known to exist for release of dopamine in vitro. These studies indicate that 3H-MMTA might serve as a useful tool with which to study dopamine release mechanisms in vitro.

[Effects of diazepam on six drug-induced locomotor hyperactivities in mice (author's transl)]

Experiments were carried out in mice to investigate the influence of diazepam (DZP) on dexamphetamine, parachloro-N-methylamphetamine (pCMA), cocaine, morphine, trihexyphenidyl or (in MAOIs pretreated) reserpine induced motor hyperactivity. The interaction of DZP with these hyperactivities in which probably different biochemical central mechanisms are involved allows to construct a profile of action of DZP and to approach its mechanism of action. The locomotor hyperactivities induced by dexamphetamine, pCMA, morphine, cocaine were not reduced by DZP even by doses which decrease spontaneous locomotor activity; low doses of DZP enhance the hyperactivity induced by these compounds. Those induced by trihexyphenidyle or by reserpine (after MAOI) were reduced by DZP at doses which produce no decrease in spontaneous motor activity. Inasmuch as DZP at low doses potentiates the effects of 4 different substances, the results can hardly be satisfactorily explained neither by an interference of the benzodiazepine on the metabolism of the drugs or by a depression of the anxiogenic action of dexamphetamine. Even though it may be difficult to relate the antagonism of DZP on trihexyphenidyl- or on reserpine- (after MAOI) induced motor hyperactivity to the suggested anticholinergic and dopaminergic actions of DZP, these effects may partly be involved in the increase in locomotor hyperactivity induced by dexamphetamine, morphine, or cocaine. The observed effect of DZP on pCMA induced locomotor hyperactivity does not support a possible antiserotonine action often suggested to explain the effects of benzodiazepines in conflict situations.

Brain receptors for antipsychotic drugs and dopamine: direct binding assays

In order to test the suggestion that antipsychotic drugs act by blocking dopamine receptors in the brain, the direct effects of such neuroleptic drugs were tested on the stereospecific binding of [3H]dopamine and of [3H]haloperidol to rat brain striata and their subfractions. The stereospecific component of binding was defined as that amount of [3h]dopamine or [3H]haloperidol bound in the presence of (-)-butaclamol (an inactive drug) minus that bound in the presence of (+)-butaclamol (a potent neuroleptic drug); 100 nM butaclamol was used for the [3H]haloperidol assay, while 1 muM butaclamol was used for the [3H]dopamine assay. Various antipsychotic drugs inhibited this stereospecific component in both the dopamine and haloperidol assays. These inhibitory potencies correlated with the clinical doses used for controlling schizophrenia.

Inhibition of synaptosomal accumulation of l-norepinephrine. I: N-arylalkyl and N-aryloxyalkyl dl-amphetamines and related compounds

The ability of a group of systematically modified amphetamines to inhibit the accumulation of l-norepinephrine by nonstriatal synaptosomes was investigated. N-Substitution by the proper bulky hydrophobic groups can be well tolerated. Structure-activity relationships generate a qualitative picture of the inhibitor-carrier interaction site.

The role of dopamine and noradrenaline in temperature control of normal and reserpine-pretreated mice

Drugs with the common property of stimulating dopamine receptors, have been tested for their effects on core temperature in control and reserpine-pretreated mice. Apomorphine, amantadine, amphetamine, L-dopa and atropine all produced a fall in mouse oesophageal temperature, their efficacy correlating with their ability to activate central dopamine receptors. Amphetamine and L-dopa had a biphasic effect the initial fall being followed by a rise. In reserpine-pretreated mice only amphetamine, apomorphine, L-dopa and D.L-threo-dihydroxyphenyl-serine effectively reversed hypothermia. Amphetamine had the highest efficacy of all the drugs tested. The sum of the effects of apomorphine and D.L-threo-dihydroxyphenylserine was equivalent to the effect of amphetamine alone. It is suggested that in control mice dopaminergic mechanisms mediate the hypothermia and noradrenergic mechanisms the hyperthermia. In reserpine-pretreated mice both systems are involved in the mechanisms restoring body temperature to normal.

Differential antagonism by the antichlolinergic dexetimide of inhibitory effects of haloperidol and fentanyl on brain self-stimulation

Haloperidol (0.08 mg/kg) or fentanyl (0.16 mg/kg) injected subcutaneously suppressed bar-pressing for brain-stimulation in rats, implanted with electrodes in the lateral hypothalamic area of the medial forebrain bundle. Increasing doses: 0.04, 0.16, 0.63 and 2.50 mg/kg of the central anticholinergic dexetimide gradually antagonized the haloperidol effects. The highest dose of dexetimide did not reduce the fentanyl-induced inhibition. The results, together with a literature survey on the anticholinergic effects on neuroleptic-induced catalepsy and inhibition of avoidance behavior, are related to biochemical findings and clinical effects.

Adenosine 3',5'-monophosphate content in rat caudate nucleus: demonstration of dopaminergic and adrenergic receptors

Dopamine, apomorphine, isoproterenol, and norepinephrine each increased the concentration of adenosine 3',5'-monophosphate in slice of rat caudate nucleus. The concentrations of dopamine, apomorphine isoproterenol, and norepinephrine causing half-maximal increases were 60, 150, 0.03 and 30 micromoles per liter, respectively. The effect of dopamine was blocked by fluphenazine, a dopamine receptor antagonist, but not by propranolol, a beta-andrenergic receptor antagonist. Conversely, the effect of isoproterenol was blocked by propranolol but not by fluphenazine. The results suggest that in rat caudate nucleus there are two distinct catecholamine receptors capable of causing increased concentrations of adenosine 3',5'-monophosphate, one having the characteristic of dopamine receptor, and the other having the characteristics of beta-adrenergic receptor.

Use of cerebrospinal fluid drawn at pneumoencephalography in the study of monoamine metabolism in man

Concentrations of homovanillic acid (HVA) and 5-hydroxyindoleacetic acid (5-HIAA) were significantly higher in CSF obtained after injection of air during pneumoencephalography (PEG) than in lumbar CSF, as drawn before the injection. There was a high correlation between levels in the `mixed' and lumbar samples of CSF in the case of each of the two acids. The concentration of lumbar HVA, but not that of 5-HIAA, was negatively correlated with CSF pressure. 5-HIAA levels were low in both samples of CSF in a group of epileptics, by comparison with controls. In two patients with Kufs disease and in one with Niemann-Pick disease, the concentration of HVA was very low in the lumbar sample. The application of a standardized PEG technique in the study of monoamine metabolism in man is suggested.