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PubMed1997

Double-blind comparison of pramipexole and bromocriptine treatment with placebo in advanced Parkinson's disease. International Pramipexole-Bromocriptine Study Group.

Pramipexole is a new, selective, nonergoline dopamine agonist that acts on D2 and preferentially on D3 dopamine receptors. Phase II and III clinical trials have shown this drug to be useful in treating both early and advanced Parkinson's disease (PD) patients. A double-blind, randomized, multicenter study was performed to compare the safety, tolerance, and efficacy of pramipexole versus placebo in patients with advanced PD with motor fluctuations. A bromocriptine treatment group was included to enable comparisons between bromocriptine and placebo groups, but the study was not powered to show statistical differences between the active treatment groups. The study included 247 patients with "wearing off." Patients were Hoehn and Yahr stages II to IV during "on" times. The trial included three phases: dose escalation, 6 months' maintenance, and dose reduction. The primary end points were the Unified Parkinson's Disease Rating Scale (UPDRS) parts II and III. Up to 4.5 mg per day of pramipexole and 30 mg per day of bromocriptine were used. The results of the study showed that the UPDRS part II improved by 26.7% for pramipexole (p = 0.0002) and 14% for bromocriptine (p = 0.02) versus 4.8% for placebo. The UPDRS part III showed improvements of 34% for pramipexole (p = 0.0006) and 23.8% for bromocriptine (p = 0.01) versus 5.7% for placebo. There were no major differences in safety data. In the active treatment groups there were more reports of dyskinesia and nausea compared with placebo. In regard to comparison of the Global Clinical Assessment of Efficacy between active treatment groups, there was a trend to significance (p = 0.056) in favor of pramipexole. We conclude that pramipexole-treated patients with advanced PD improved significantly more than placebo for both primary end points.

Adult↗
PubMed1997

Efficacy of pramipexole, a novel dopamine agonist, as monotherapy in mild to moderate Parkinson's disease. The Pramipexole Study Group.

A total of 335 patients with early Parkinson's disease (PD) were enrolled in a multicenter, randomized, double-blind trial designed to assess the efficacy and safety of pramipexole. Entry was restricted to patients with idiopathic PD who were not receiving levodopa. Pramipexole was administered according to an ascending dose schedule up to 4.5 mg/d. During the 7-week dose-escalation phase, each subject was titrated to his or her maximally tolerated dose of study medication. This was followed by a 24-week period of maintenance therapy. The mean daily dose during the maintenance period was 3.8 mg. Pramipexole significantly reduced the severity of PD symptoms and signs compared with placebo, as measured by decreases in parts II (Activities of Daily Living) and III (Motor Examination) of the Unified Parkinson's Disease Rating Scale at week 24 compared with baseline (p < or = 0.0001). Differences between the active drug and placebo groups emerged at week 3 (1.5 mg/d) in the ascending-dose interval and persisted throughout the maintenance phase (p < or = 0.0001). The majority of patients completed the study (pramipexole 83%, placebo 80%). In the assessment of adverse events, nausea, insomnia, constipation, somnolence, and visual hallucinations occurred more frequently in the pramipexole treatment group compared with placebo patients. No clinically significant changes were noted in blood pressure or pulse rate. Overall, these results indicate that pramipexole is safe and effective in the treatment of early PD.

Activities of Daily Living↗
PubMed1998

Pramipexole. A review of its use in the management of early and advanced Parkinson's disease.

UNLABELLED: Pramipexole is an orally active non-ergoline dopamine agonist with selective activity at dopamine receptors belonging to the D2 receptor subfamily (D2, D3, D4 receptor subtypes) and with preferential affinity for the D3 receptor subtype. It is approved as monotherapy in early Parkinson's disease and as adjunctive therapy to levodopa in patients with advanced disease experiencing motor effects because of diminished response to levodopa. The potential neuroprotective effects of pramipexole have been shown in animal and in vitro studies. Data from relatively long term (10- or 31-week) studies suggest that pramipexole monotherapy (0.375 to 6.0 mg/day) can improve activities of daily living and motor symptoms in patients with early Parkinson's disease. Pramipexole (0.375 to 4.5 mg/day for 31 or 36 weeks), as an adjunct to levodopa in advanced disease, improved activities of daily living and motor symptoms, reduced the duration and severity of 'off' periods and allowed a reduction in levodopa dosage. Mentation, behaviour and mood [Unified Parkinson's Disease Rating Scale (UPDRS) part I], and timed walking test were not significantly improved. The extent of disability improved according to the UPDRS parts II and III but, when assessed by secondary efficacy parameters, it is unclear whether disability or the severity of disease improved. No significant differences were observed in patients randomised to pramipexole or bromocriptine according to a secondary hypothesis in a prospective study in which both drugs were better than placebo. Some quality-of-life measures improved with active treatment relative to placebo. Further studies comparing pramipexole with other dopamine agonists and levodopa in patients with early and advanced Parkinson's disease would be useful. In pramipexole recipients with early disease, the most commonly experienced adverse events were nausea, dizziness, somnolence, insomnia, constipation, asthenia and hallucinations. The most commonly reported adverse events in pramipexole recipients with advanced disease were orthostatic hypotension, dyskinesias, extrapyramidal syndrome (defined as a worsening of the Parkinson's disease), dizziness, hallucinations, accidental injury, dream abnormalities, confusion, constipation, asthenia, somnolence, dystonia, gait abnormality, hypertonia, dry mouth, amnesia and urinary frequency. The incidence of some adverse events did not greatly differ between pramipexole and placebo recipients. CONCLUSIONS: Pramipexole is effective as adjunctive therapy to levodopa in patients with advanced Parkinson's disease. However, the potential beneficial effects of pramipexole on disease progression need to be confirmed in clinical studies. The efficacy of pramipexole monotherapy in patients with early disease has also been demonstrated, although the use of dopamine agonists in early Parkinson's disease remains controversial.

Antiparkinson Agents↗
PubMed1997

The behavioural effects of pramipexole, a novel dopamine receptor agonist.

Pramipexole (SND 919; 2-amino-4,5,6,7-tetrahydro-6-propyl-amino-benzthiazole-dihydroc hlo ride) is a novel dopamine D2 family receptor agonist with a predominant action on D2 autoreceptors and with some D3 vs. D2 receptor preference. The central behavioural effects of pramipexole given subcutaneously to rats (male Wistar) and mice (Albino Swiss) are presented in this paper. Used in low doses (0.001-0.1 mg/kg), pramipexole induced locomotor hypoactivity which was antagonized by a low dose of spiperone; at higher doses (0.3, 1 mg/kg) it evoked hyperactivity which was inhibited by haloperidol, sulpiride and clozapine, but not by SCH 23390 (R(+)-7-chloro-8-hydroxy-3-methyl-1-phenyl-2,3,4,5-tetrahydro-1H-3- benzazepine hydrochloride). Pramipexole (0.1-1.0 mg/kg) antagonized the akinesia induced by combined pretreatment with reserpine (5 mg/kg) and alpha-methyl-p-tyrosine (250 mg/kg). Pramipexole (0.1-1 mg/kg) potentiated the hyperkinetic effect of L-DOPA (L-3,4-dihydroxyphenylalanine) (50 and 200 mg/kg, together with benserazide, 50 mg/kg) in naive and monoamine-depleted (reserpine + alpha-methyl-p-tyrosine) rats. The higher doses of pramipexole (1 and 3 mg/kg) evoked stereotypy which was antagonized by pretreatment with sulpiride or clozapine. The catalepsy induced by haloperidol, spiperone or fluphenazine was antagonized by pramipexole (1-3 mg/kg). Pramipexole (1 mg/kg) induced hypothermia in mice, which was antagonized by sulpiride. The obtained results indicate that pramipexole: (i) at low doses stimulates the dopamine D2 presynaptic autoreceptors; (ii) at higher doses stimulates dopamine D2 postsynaptic receptors. An effect on the dopamine D3 receptor cannot be excluded. At low doses pramipexole may have antipsychotic activity, and at higher ones antiparkinsonian activity.

Animals↗
PubMed1995

Pramipexole in patients with early Parkinson's disease.

We evaluated the efficacy, safety, tolerability, and pharmacokinetics of pramipexole, a novel dopamine D2 receptor agonist, in early Parkinson's disease (PD). The study design was a parallel, placebo-controlled trial using an ascending dose of 4.5 mg/day pramipexole maximum. All subjects received selegiline (10 mg/day) but were not treated with levodopa. Of the 55 subjects who received at least one dose of the study medication, all but one, in the placebo group, completed the trial, which was 9 weeks in duration. The primary efficacy endpoints were changes in scores from baseline to final measurement on the Unified Parkinson's Disease Rating Scale (UPDRS) Parts II and III. The pramipexole group had a significantly greater improvement (p = 0.002) than the placebo group on UPDRS Part II (Activities of Daily Living). The change in score from baseline to final measurement on UPDRS Part III (Motor Examination) was not significantly different (p = 0.10) between the pramipexole and placebo groups, although the trend favoured the pramipexole group. All subjects in both the pramipexole and the placebo groups experienced one or more episodes of asymptomatic orthostatic hypotension; there was no significant difference between the pramipexole and the placebo groups in the number of subjects experiencing symptomatic orthostatic hypotension. The adverse events profile of pramipexole was similar, in general, to that of other dopamine receptor agonists. Plasma pramipexole levels increased linearly with dose. Pramipexole appears to be promising agent in the treatment of early PD.

Adult↗
PubMed1990

Effect of pramipexole, a dopamine-1/dopamine-2 receptor agonist, on sodium excretion and blood pressure in spontaneously hypertensive rats.

1. Abnormalities of the renal dopaminergic system have been implicated in the pathogenesis of hypertension in the spontaneously hypertensive rat (SHR). 2. Both DA-1 and DA-2 receptors are present in renal tubules and blood vessels. DA-1 receptors mediate the renal vasodilatory and natriuretic effects of DA but the contribution of DA-2 receptors to these effects is not known. 3. We therefore studied the effect of a novel and selective DA-1 and DA-2 agonist, pramipexole, on MAP, glomerular filtration rate (GFR), urine flow (V), absolute (UNaV) and fractional sodium (FeNa) excretion in 9-18-week-old SHR. Wistar-Kyoto rats (WKY) served as control. 4. Pramipexole given intravenously (1, 10, 100 micrograms kg body wt-1 min-1) decreased MAP in a dose-related manner to a greater extent in SHR (n = 5) than WKY (n = 6) such that at the highest dose of pramipexole, MAP was similar in both groups. Pramipexole did not alter GFR in either WKY or SHR. Pramipexole increased V in a dose-related manner in both WKY and SHR. At 100 micrograms pramipexole kg body wt-1 min-1, V increased eightfold in both SHR and WKY. In contrast, pramipexole increased UNaV to a greater extent in WKY (5.1-fold) than SHR (3.7-fold). 5. These studies show a differential effect of pramipexole on renal function and MAP in SHR and WKY. Pramipexole has a more potent blood pressure lowering effect in SHR than in WKY. However, the natriuretic effect of pramipexole was greater in the WKY than in the SHR.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

Reversal of stress-induced anhedonia by the dopamine receptor agonist, pramipexole.

Chronic exposure to mild unpredictable stress has previously been found to depress the consumption of a palatable (1%) sucrose solution, and to attenuate food-induced place preference conditioning. In this study the effects of pramipexole (SND-919), a dopamine D2 agonist, were studied during 7-9 weeks of chronic treatment. Pramipexole (1.0 mg/kg per day) reversed the suppression of sucrose intake in stressed animals, increasing sucrose intakes above the levels seen in untreated nonstressed controls. Pramipexole also increased sucrose intake in nonstressed animals; these effects were accompanied by increases in water intake and tended to correlate with weight loss. Drug-treated stressed animals also lost weight, but in this case water intake was unaffected. A second group of animals received a higher dose of pramipexole (2.0 mg/kg per day). The effects of the two doses were very similar. After three weeks of treatment, these animals were switched to a lower dose of pramipexole (0.1 mg/kg per day). Increases in sucrose intake were maintained over three weeks of treatment at the lower dose, with significant recovery of body weight. Two further groups received the same doses of pramipexole (1.0 mg/kg for 6 weeks or 2.0 mg/kg for 3 weeks followed by 0.1 mg/kg thereafter), but received intermittent (twice-weekly) drug treatment. Intermittent pramipexole treatments also tended to increase sucrose intakes, but the results were less consistent from week to week. Following 6-8 weeks of pramipexole treatment, food-induced place preference conditioning was studied in all animals.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1995

Pramipexole binding and activation of cloned and expressed dopamine D2, D3 and D4 receptors.

Pramipexole (SND 919; 2-amino-4,5,6,7-tetrahydro-6-propylamino-benzthiazole-dihydrochlor ide) is a potent dopamine autoreceptor agonist. We have carried out an analysis of the binding affinities of dopamine D2L, D2S, D3, and D4 receptors for pramipexole using both [3H]pramipexole and [3H]spiperone as radioligands at cloned and heterologously expressed receptors. Studies were carried out using rat and human D2L, D2S and D3 receptors with equivalent results. When the binding of pramipexole to the high affinity, guanine nucleotide-sensitive state of each receptor was analyzed, pramipexole is most selective for D3 compared to D2 and D4 receptors. These results indicate a 5-fold selectivity of pramipexole for D3 receptors, while quinpirole and bromocriptine are non-selective or more D2/D4 receptor selective. Two measurements of receptor activation for dopamine D2, D3, and D4 receptors also show that pramipexole is most potent for activation of D3 receptors. The dopamine D3 receptor selectivity of pramipexole may explain the previously described properties of this drug, including its potent autoreceptor preference.

Animals↗
PubMed1992

Biochemical and pharmacological studies on pramipexole, a potent and selective dopamine D2 receptor agonist.

Pramipexole (SND 919; 2-amino-4,5,6,7-tetrahydro-6-propyl-amino-benzthiazole- dihydrochloride) was tested for its agonistic activity at pre- and postsynaptic dopamine (DA) receptors. L-Dihydroxyphenylalanine (L-dopa) accumulation in the rat striatum and limbic system and the alpha-methyltyrosine-induced reduction of DA were inhibited. Both effects were fully antagonized by haloperidol but not by the selective DA D1 receptor antagonist SCH 23390. Pramipexole decreased the levels of DA metabolites dose dependently, whereas striatal DA levels remained unchanged. In mice, pramipexole (0.001-1 mg/kg s.c.) reduced exploratory locomotor activity. In rats with unilateral striatal lesions, only weak ipsilateral rotation was produced by pramipexole at the highest dose. However, in rats with unilateral lesions of the medial forebrain bundle, pramipexole potently induced contralateral circling (ED50 0.026 mg/kg s.c.). In the N-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) monkey model, pramipexole also had potent stimulatory effects. Finally, in haloperidol-sensitized monkeys, the substance did not elicit dyskinesia/dystonia when given alone, but rather inhibited those symptoms which had been induced by haloperidol (ED50 0.116 mg/kg i.m.). It is concluded that pramipexole has therapeutic potential for schizophrenic patients, as a result of its autoreceptor agonistic effects and its weak effects at normosensitive postsynaptic DA receptors. Furthermore, its potent stimulatory effects in DA-depleted animals suggest a possible use in the treatment of Parkinson's disease.

3,4-Dihydroxyphenylacetic Acid↗
PubMed1996

Neuroprotective effects of the dopamine D2/D3 agonist pramipexole against postischemic or methamphetamine-induced degeneration of nigrostriatal neurons.

We have examined the neuroprotective efficacy of the selective dopamine (DA) D2/D3 receptor agonist pramipexole in two models of nigrostriatal (NS) degeneration. The first involves the delayed (28-day) postischemic retrograde NS degeneration that takes place in gerbils following a 10-min episode of bilateral carotid arterial occlusion-induced forebrain ischemia. In vehicle (40% hydroxypropyl cyclodextrin)-treated male gerbils, there was a 40-45% loss of NS cell bodies in the pars compacta and pars reticulata (TH immunohistochemistry and Cresyl violet histochemistry) by 28 days after ischemia/reperfusion. Daily postischemic oral dosing (1 mg/kg p.o., b.i.d., beginning at 1 h after insult) decreased the 28-day postischemic loss of NS DA neurons by 36% (P < 0.01 vs. vehicle-treated). The effect was specific for dopamine neurons since no significant salvage of hippocampal CA1 neurons was observed. In a second model, pramipexole's effects were examined on methamphetamine-induced (10 mg/kg, i.p. X 4, each 2 h apart) NS degeneration in male Swiss-Webster mice. In vehicle-treated mice, there was a 40% loss of NS neurons by day 5. In contrast, pramipexole dosing (1 mg/kg, p.o., 1 h after the last methamphetamine dose, plus daily) attenuated the NS degeneration from 40% to only 8% (P < 0.00001 vs. vehicle). We postulated that pramipexole acts in both of these models to reduce the elevated DA turnover and the associated elevation in hydroxyl radical production secondary to increased MAO activity that could be responsible for oxidative damage to the NS neurons. Indeed, in the gerbil ischemia model, we documented by HPLC-ECD a 135% postreperfusion increase in DA turnover (DOPAC + HVA/DA) at 5 min after reperfusion. Pramipexole at the 1 mg/kg, p.o., dose level was able to significantly reduce the increased DA turnover, but by only 16%. Thus, it is conceivable that other mechanisms may also contribute to pramipexole's dopaminergic neuroprotection. Based on a preliminary examination of pramipexole's oxidation potential, it appears that the compound may possess significant intrinsic antioxidant properties that might contribute to its neuroprotective effects.

Animals↗
PubMed1999

Pramipexole--a new dopamine agonist for the treatment of Parkinson's disease.

Although L-DOPA is the current 'gold standard' for treatment of Parkinson's disease, its effectiveness fades rapidly and its use results in serious motor fluctuations (on-off, wearing off, freezing, involuntary movements) for most patients with Parkinson's disease. Pramipexole is an aminothiazole dopamine agonist with selective actions at dopamine receptors belonging to the D2 subfamily, where it possesses full activity similar to dopamine itself. Pramipexole's preferential affinity for the D3 receptor subtype could contribute to efficacy in the treatment of both the motor and psychiatric symptoms of Parkinson's disease. Both in vitro and in vivo studies in animals suggest that pramipexole possesses numerous neuroprotective properties, including dopamine autoreceptor agonist properties, antioxidant properties, ability to block the mitochondrial permeability transition pore and the ability to stimulate the release of trophic factors. Clinical studies have demonstrated that pramipexole has excellent pharmacokinetic properties and that it is an effective monotherapy in treating early Parkinson's disease and an effective adjunctive therapy with L-DOPA in treating late Parkinson's disease. In addition, pramipexole has demonstrated efficacy in a clinical trial for the treatment of major depression. In the early disease studies, pramipexole was able to retard the need for L-DOPA treatment for several years. Thus, a new 'L-DOPA-sparing' paradigm for treating Parkinson's disease may now be possible, whereby patients are initially treated with pramipexole and L-DOPA is added only as necessary.

Animals↗
PubMed1999

Neuroprotection by pramipexole against dopamine- and levodopa-induced cytotoxicity.

Pramipexole, a novel non-ergoline dopamine (DA) agonist, has been applied successfully for treatment of Parkinson's disease (PD). We report here that pramipexole can protect dopaminergic cell line Mes23.5 against dopamine- and levodopa-induced cytotoxicity possibly through a mechanism related to antioxidant activity. In the MES 23.5 cultures, DA and L-DOPA induce a dose- and time-dependent cytotoxicity, as determined by tetrazolium salt and trypan blue assays. Furthermore, an in situ terminal deoxynucleotidyl transferase assay demonstrates that DA-induced cell death is apoptotic. Pretreatment with pramipexole in a concentration range (4-100 microM) significantly attenuates DA- or L-DOPA-induced cytotoxicity and apoptosis, an action which is not blocked by D3 antagonist U-99194 A or D2 antagonist raclopride. Pramipexole also protects MES 23.5 cells from hydrogen peroxide-induced cytotoxicity in a dose-dependent manner. In cell-free system, pramipexole can effectively inhibit the formation of melanin, an end product resulting from DA or L-DOPA oxidation. These results indicate that pramipexole exerts its neuroprotective effect possibly through a mechanism, which is independent of DA receptors but related to antioxidation or scavenging of free radicals (e.g. hydrogen peroxide). As a direct DA agonist and potentially neuroprotective agent, pramipexole remains attractive in the treatment of PD.

Animals↗
PubMed1999

Efficacy, safety, and tolerance of the non-ergoline dopamine agonist pramipexole in the treatment of advanced Parkinson's disease: a double blind, placebo controlled, randomised, multicentre study.

OBJECTIVES: Pramipexole, a non-ergot dopamine D2/D3 receptor agonist, was investigated as an add on drug in advanced parkinsonian patients with motor fluctuations to assess efficacy, safety, and tolerance. METHODS: Seventy eight patients of either sex with advanced Parkinson's disease and treatment complications such as motor fluctuations were enrolled into a double blind, placebo controlled, randomised, multicentre study (phase II) and assigned to add on treatment with pramipexole (n=34) versus placebo (n=44) to a previously stabilised antiparkinsonian medication (7 week dose titration interval, 4 week maintenance period). The primary end point of efficacy was the change from baseline in the total score of the unified Parkinson's disease rating scale (UPDRS) in the on "period" (2 hours after intake of study medication). Safety and tolerability were assessed on the basis of adverse events, vital signs, laboratory measurements, and ECG recordings. RESULTS: There was a significant improvement of the pramipexole group in UPDRS total scores, subscores part II, III (activities of daily living and motor examination), and IV (complications of therapy). Mean UPDRS total score decreased by 37.3% under pramipexole compared with 12.2% under placebo (p<0.001). Patients under pramipexole reported an overall reduction in "off" periods of 12%--resulting in 1.7 more hours "on" time a day--compared with an increase in "off" periods of 2% under placebo. There were no unexpected safety results. The adverse event profile disclosed a high tolerability. The most important adverse events under pramipexole were fatigue, dyskinesia, and vivid dreams. CONCLUSION: Pramipexole administration is an efficacious and well tolerated add on therapy in patients with advanced Parkinson's disease with an improvement in activities of daily living, motor function, and treatment associated complications.

Adult↗
PubMed1997

Safety and efficacy of pramipexole in early Parkinson disease. A randomized dose-ranging study. Parkinson Study Group.

CONTEXT: Monotherapy with dopamine agonists may be useful in early Parkinson disease. OBJECTIVE: To evaluate dose-response relationships for tolerability, safety, and efficacy of the synthetic dopamine agonist pramipexole. DESIGN: Multicenter, multidosage, parallel-group, double-blind, placebo-controlled, randomized clinical trial. SETTING: University or academically based movement disorder clinics. PATIENTS: A total of 264 patients with early Parkinson disease (PD) who were not requiring or receiving levodopa or other dopamine agonists were enrolled. INTERVENTION: Subjects were randomized to 1 of 5 treatment groups: pramipexole doses of 1.5 mg/d, 3.0 mg/d, 4.5 mg/d, and 6.0 mg/d, or matching placebo. A 6-week dosage escalation period was followed by a 4-week maintenance period and a 1-week period during which active treatment was withdrawn. MAIN OUTCOME MEASURES: The primary measure of tolerability was the proportion of subjects completing the study on the assigned treatment. The primary measure of efficacy was the change from baseline to 10 weeks in the total score on the Unified Parkinson's Disease Rating Scale (UPDRS). RESULTS: Pramipexole was generally safe and well tolerated in this 10-week study. The proportion of subjects completing the study on the originally assigned dosage was 98% for placebo and 81% for the 1.5-mg/d, 92% for the 3.0-mg/d, 78% for the 4.5-mg/d, and 67% for the 6.0-mg/d treatment groups. There was a trend toward increased frequency of adverse experiences, particularly somnolence, in the 6.0-mg/d group. After 10 weeks of treatment, pramipexole-treated subjects showed a 20% improvement in total UPDRS scores, with mean improvements in scores ranging from 5.9 to 7.0 units among active treatment groups, compared with 0.9 units for the placebo group (P<.005 for each comparison with placebo). There was also evidence that the treatment effects were more pronounced in subjects with worse UPDRS scores at baseline. CONCLUSIONS: Pramipexole is safe and effective as short-term monotherapy in patients with early PD who are not receiving levodopa. Further study is warranted to determine the long-term impact of pramipexole on the progression of disability in PD and its value in comparison with levodopa therapy and other dopamine agonists.

Aged↗
PubMed1997

Attenuation of levodopa-induced toxicity in mesencephalic cultures by pramipexole.

The direct-acting dopamine (DA) agonist pramipexole (2 amino-4,5,6,7-tetrahydro-6-propyl-amino-benzthiazole-dihydrochlori de) was evaluated for its ability to attenuate levodopa-induced loss of tyrosine hydroxylase immunoreactive (THir, a marker for dopamine neurons) cells in mesencephalic cultures. Pramipexole reduced levodopa-induced THir cell loss in a dose-dependent and saturable fashion (ED50 = 500 pM), its inactive stereoisomer was significantly less potent in this regard and pergolide and bromocriptine had negligible cytoprotective effects. Culture media from mesencephalic cultures incubated with pramipexole for 6 days increased THir cell counts in freshly harvested recipient cultures. The magnitude of this effect was directly proportional to the amount of pramipexole in the donor cultures and heat-inactivation of the media abolished the growth promoting effect. The results from this exploratory set of experiments suggest that pramipexole may be cytoprotective to dopamine neurons in tissue culture. Pramipexole's affinity for DA receptors, its antioxidant action or its ability to enhance mesencephalic trophic activity could be responsible for this effect.

Animals↗
PubMed1997

Antidepressant effects of pramipexole, a novel dopamine receptor agonist.

Pramipexole (2-amino-4,5,6,7-tetrahydro-6-propyl-amino-benzthiazole-dihydrochl oride), a new dopamine receptor agonist with preference for D3 compared to D2 and D4 receptors, was tested in rats in respect of its potential antidepressant activity. In the forced swimming test the drug under study, given three times in rats, reduced the immobility time. In the forced swimming test, joint treatment with antidepressants (imipramine, amitriptyline) and pramipexole evoked a more potent effect than any of the drugs given alone; however, the locomotor hyperactivity was weaker after joint administration. Citalopram and fluoxetine, inactive per se in the forced swimming tests, visibly enhanced the antidepressant-like effect of pramipexole but, on the other hand, they attenuated the locomotor hyperactivity evoked by the drug. Repeated treatment with pramipexole (0.3 or 1 mg/kg, twice daily for 14 days) increased the locomotor activity measured at 1 h after the last dose. Repeated administration of pramipexole (as above) potentiated the D-amphetamine- or quinpirole-induced locomotor hyperactivity. The obtained results indicate that, in the tests used, pramipexole evokes effects similar to those of typical antidepressants and, at the same time, enhances their activity (the forced swimming test in rats); therefore it may be regarded as a potential antidepressant drug.

Animals↗
PubMed1991

Pramipexole, a dopamine D2 autoreceptor agonist, decreases the extracellular concentration of dopamine in vivo.

Pramipexole (SND 919) is a dopamine D2 autoreceptor agonist which is structurally related to talipexole (B-HT 920), a potential antipsychotic agent. The aim of this study was to investigate the effects of pramipexole on the extracellular concentration of dopamine in vivo. Dopamine and its metabolites, 3,4-dihydrophenylacetic acid and homovanillic acid, were measured in the anterior striatum of freely moving rats by microdialysis and high-performance liquid chromatography with electrochemical detection. Pramipexole (30 and 100 micrograms/kg) caused long-lasting decreases in the extracellular concentrations of dopamine and its metabolites. Talipexole (30 micrograms/kg) produced similar effects. Sulpiride (5 mg/kg), a selective dopamine D2 antagonist, caused a transient increase in the concentration of dopamine and long-lasting increases in the concentrations of its metabolites; it also reversed the effects of pramipexole. SCH-23390 (100 micrograms/kg), a selective dopamine D1 receptor antagonist, caused a transient increase in the concentration of dopamine but did not affect the concentrations of the metabolites. SCH-23390 failed to reverse the effects of pramipexole. These results indicate that pramipexole reduces the extracellular concentrations of dopamine and its metabolites in vivo through a reversible interaction with the dopamine D2 receptor.

3,4-Dihydroxyphenylacetic Acid↗
PubMedDate not supplied

Pharmacology of pramipexole, a dopamine D3-preferring agonist useful in treating Parkinson's disease.

Pramipexole is a clinically effective nonergot dopamine agonist. Pramipexole's receptor interactions differ from ergot agonists in several ways. First, it has high selectivity for interacting with dopamine D2 subfamily receptors (D2, D3, and D4 receptor subtypes) and has little interaction with adrenergic or serotonergic receptors. Second, within the D2 subfamily, it has preferential affinity for the D3 receptor subtype, which, according to preclinical studies, could contribute additional efficacy for treatment of both motor and psychiatric syndromes in Parkinson's disease. Third, it has full intrinsic activity at dopamine D2 subfamily receptors. In addition to pramipexole's unusual receptor profile, whole-animal and cell culture studies suggest that pramipexole might provide neuroprotective effects through depression of dopamine metabolism, antioxidant effects, and stimulation of trophic activity. Pramipexole's demonstrated clinical efficacy for successful treatment in early disease for several years in the absence of L-dopa and as adjunctive therapy with L-dopa in late disease suggests a potential new paradigm for treatment of Parkinson's disease whereby new patients are initiated with pramipexole therapy and L-dopa is added only as necessary.

Aged↗