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Biomedical subjects

R Horowski

Publications and source records attributed to R Horowski.

At least 55 records · Page 3Linked to original sources
PubMed1985

Effects of lisuride on blink reflex habituation in Parkinson disease.

The blink reflex presents a tendency to habituation (a gradual diminution of the amplitude of the response during repetitive stimulation). Electromyographic analysis of this reflex makes it possible to quantify this phenomenon. A lack of the habituation of the blink reflex is a typical feature of Parkinson disease. L-Dopa and amantadine, but not anticholinergic drugs, are able to partly reverse these abnormalities in blink reflex habituation to a normal pattern. Lisuride, a dopamine agonist with serotoninergic activity, has been recently proposed as antiparkinsonian agent. In our study we observed that lisuride has a positive effect on blink reflex habituation in Parkinson disease. A good correlation between the improvement of this electrophysiological parameter and clinical akinesia was seen. Mechanisms underlying the therapeutic effect of lisuride are complex, but this drug usually has a postsynaptic effect on D2 receptors. Our data suggest that these receptors play an important role in blink reflex habituation.

Adult↗
PubMed1983

Lisuride in the treatment of parkinsonism.

Lisuride is a new effective antiparkinson agent that is useful in the management of patients in an advanced stage of parkinsonism where levodopa therapy is no longer sufficient and/or limited by 'wearing off' reactions. Patients with these problems usually respond favorably to 1.5-4.5 mg of lisuride daily provided the daily dose is built up gradually over a period of 4-8 weeks. All the clinical features of parkinsonism may be improved and the daily dose of levodopa may be reduced by 30-40%. In some instances it may be possible to give lisuride as a replacement for levodopa. Less established, however, is the potential role of lisuride in treating patients in the early stages of parkinsonism and the long-term effects of lisuride. And, as with other ergots, caution should be exercised in using lisuride if patients have a history of hypotension, hepatic dysfunction, cardiac arrhythmias, and dementia. Finally, lisuride, unlike other drugs, is highly water soluble with a nearly immediate outset of antiparkinsonian action when given intravenously and may therefore be of considerable value in the emergency treatment of severe parkinsonism.

Administration, Oral↗
PubMed1983

Influence of ergot derivatives on prolactin secretion in rats. Mechanisms of action and clinical implications.

Ergot derivatives are the most effective compounds in the treatment of migraine attacks. It has been proposed that these compounds exert this effect by direct action on skull arteries or arteriovenous anastomoses, or by interfering with peripheral or central serotonin receptors. It is also possible that these compounds influence monoaminergic neurotransmission and, thereby, endorphins modulating the threshold for pain or sensory perception. In testing these hypotheses, changes in receptor sensitivity or function have to be considered since we have observed simultaneous tolerance and supersensitivity development in the same animal treated chronically with lisuride. We therefore propose that ergot derivatives can reduce the well documented higher sensitivity of migraine sufferers to various stimuli. In humans, prolactin-levels can be used for determining bioavailability of some ergot derivatives and for studying whether dopaminergic mechanism plays a role in their antimigraine effect.

Animals↗
PubMed1982

Effect of metoclopramide and lisuride on hypophyseal and gonadal function in men.

The effects of chronic treatment over 7 weeks with metoclopramide and lisuride alone as well as the combination of both drugs were studied on basal and TRH/LHRH stimulated serum PRL, testosterone, LH, FSH, GH, and TSH concentrations. The study was conducted under double-blind placebo-controlled conditions and included twenty-four healthy male volunteers. In addition, repeated seminal fluid analyses were performed before, during and after treatment. While the known PRL-stimulatory effect of metoclopramide and the PRL-lowering effect of lisuride could be confirmed, we were unable to demonstrate any substance-related effects on the other hypophyseal or gonadal hormones. In contrast to previously published data no adverse effects of metoclopramide on sperm analysis could be demonstrated.

Adult↗
PubMed1981

Effects of lisuride and bromocriptine on inhibition of lactation and on serum prolactin levels: comparative double-blind study.

The effects of lisuride (Schering) and bromocriptine (Parlodel, Sandoz), two dopaminergic drugs, on the inhibition of puerperal lactation were compared in a double-blind study. At the dosages selected, lisuride was as effective as bromocriptine for the inhibition of lactation but bromocriptine was more effective in lowering serum prolactin levels.

Bromocriptine↗
PubMed1981

Size reduction of macroprolactinomas by bromocriptine or lisuride treatment.

We have administered to 29 patients with macroprolactinoma the dopamine agonists bromocriptine and lisuride for 1-50 months (mean +/- SE, 12.7 +/- 1.8) in order to assess the effects of these drugs on tumor size. Fourteen patients were treated with bromocriptine (dose range, 7.5-20 mg/day), 12 patients were treated with lisuride (0.6-2 mg/day), and 3 patients were given both drugs. Computed tomography performed before and during treatment showed the occurrence of tumor shrinkage in 18 patients (62%), but in no case was a complete disappearance of the tumor observed. In 5 of these patients, it was even possible to document tumor shrinkage within the first month of treatment with low doses of the dopamine agonists, whereas in other patients, tumors shrank only after prolonged treatment with higher doses. Visual field and acuity improved or normalized in 8 of the 13 patients with visual defects; in some cases, the improvement was reported as early as 2 days after the treatment was started. Plasma PRL levels fell in all patients who showed a reduction in tumor size; in 2 other patients, PRL levels were only poorly suppressed, and tumor size remained unchanged. In the remaining patients, PRL levels were lowered without convincing evidence of tumor shrinkage. In considering the high percentage of patients showing tumor shrinkage under medical treatment, we propose a course with dopamine agonists as the first step in the management of patients with macroprolactinomas regardless of the presence of visual impairments.

Adolescent↗
PubMed1980

The role of D-1 and D-2 receptors.

Dopamine receptors in intracerebral motor and endocrine systems have been divided into two main types, D-1 and D-2, dependent on the presence or absence of adenylate cyclase linkage. Here we have investigated a number of dopamine agonist and antagonist drugs in man that have different actions on D-1 and D-2 receptors in animals. Motor and endocrine effects in parkinsonian subjects seem to depend on drug interaction with D-2, but not D-1, receptors. These results may have important implications for the design of anti-parkinsonian and antipsychotic agents.

Adenylyl Cyclases↗
PubMed1980

Size reduction of a prolactin secreting adenoma during long-term treatment with the dopamine agonist lisuride.

A 38-year-old amenorrhoeic woman suffering from a prolactin (PRL) secreting adenoma, which had suprasellar extension as shown by caroe agonist (lisuride). PRL levels were lowered and after 1 year of treatment CAT showed a marked reduction of the tumour size. After 2 years of treatment menstruation returned and CAT demonstrated a further reduction of the adenomatous tissue. This study supports the suggestion that dopamine agonists possess an anti-proliferative effect on tumoural lactotrophic cells of humans.

Adenoma↗
PubMed1979

Neuroendocrine effects of neuropsychotropic drugs and their possible influence on toxic reactions in animals and man -- the role of the dopamine-prolactin system.

As an example for the importance of the neuroendocrine system in the toxicological evaluation of neuropsychotropic drugs, the influence of functional dopaminergic agonists and antagonists on the secretion of prolactin is studied. In rats, all functional dopamine antagonists (reserpine alone or combined with alpha-methyl-p-tyrosine or benserazide, haloperidol, spiroperidol, sulpiride) increased serum PRL levels. Dopaminergic agonists (apomorphine, piribedil, d-amphetamine, L-DOPA, and the ergot derivatives bromocriptine and lisuride) all caused a decrease of serum prolactin levels. The same effect could be observed also after treatment with other ergot derivatives such as d-LSD, methergoline, methysergide and ergotamine. Also in this case, the prolactin-lowering effect seems to be related to dopaminergic activity. This was suggested by the inhibitory effect of pretreatment with the dopamine antagonist spiroperidol or with sulpiride on the prolactin-lowering effect of lisuride. In dogs, thyrotropin releasing hormone (TRH) increased and lisuride decreased serum prolactin levels determined with a new radioimmunoassay. As an example for the situation in humans, the effects of the dopamine antagonist sulpiride and of the dopamine agonist bromocriptine were described. The prolactin levels were higher in the presence of estrogens. The relevance of these neuroendocrine effects of neuropsychotropic drugs on physiological systmes in animals and man is discussed.

Animals↗
PubMed1979

Hypothermic action of lisuride in rats and differences to bromocriptine in the antagonistic effect of neuroleptics.

The semisynthetic ergot derivative lisuride induced dose- and time-dependent hypothermia in rats placed in a cold environment (+4 degrees C). As regards dosage, lisuride was more than 100 times more effective in this test model than bromocriptine. The effect of both drugs could be reduced by pretreatment with the dopamine antagonist haloperidol, which indicated a dopaminergic action of both drugs. In contrast, the hypothermic effect of lisuride could not be impaired by pretreatment with sulpiride, whilst the effects of bromocriptine were clearly antagonized by this drug. This results could be explained by a different affinity of these drugs to the same receptors, or, more likely, by a different mechanism of action by which lisuride and bromocriptine activate dopaminergic systems.

Animals↗
PubMed1979

Effect of lisuride on inhibition of lactation and serum prolactin.

Lisuride, a new semisynthetic ergot derivative, was given to 53 women to inhibit lactation; 26 women had 300 micrograms daily and 27 had 600 micrograms daily for seven days. Eight lactating women acted as controls. Lisuride effectively inhibited lactation and also suppressed the serum prolactin levels; the latter effect was dose related. Lisuride produced no untoward side effects.

Chemical Phenomena↗