Interaction of ergot alkaloids and their combination (co-dergocrine) with alpha-adrenoceptors in the CNS

Dihydroergotoxine mesylate for the treatment of sialorrhea in Parkinson's disease

BACKGROUND

Many patients with Parkinson's disease (PD) suffer from sialorrhea. Sialorrhea is often treated with anticholinergics and botulinum toxin, but some adverse effects have limited the use of these treatments. Dihydroergotoxine mesylate is an α-adrenergic blocking agents as well as some affinities to the dopaminergic and serotonin (5-HT) receptors. In the current study, we examine the safety and efficacy of dihydroergotoxine mesylate in PD patients.

METHODS

This study consisted of 2 phases. The intervention was 2.5-mg oral dihydroergotoxine mesylate twice daily in both phases. The first phase is a three-week open-label single-arm trial (n = 10). The second phase was a six-week randomized controlled trials with a crossover design (n = 20). Efficacy was assessed using the United Parkinson's Disease Rating Scale (UPDRS) sialorrhrea subscore and Sialorrhea Clinical Scale for PD (SCS-PD).

RESULTS

In the first phase, the UPDRS sialorrhea score was 3.5 ± 0.53 vs. 1.9 ± 0.57 prior to and after the treatment (P = 0.004). The SCS-PD score decreased from 15.8 ± 2.78 to 9.9 ± 3.00 after the treatment (P = 0.005). The response rate (defined by at least 30% reduction in SCS-PD score) was 60%. In the second phase of crossover trial, the UPDRS sialorrhea score was 3.00 ± 0.56 in placebo weeks vs. 2.00 ± 0.65 on dihydroergotoxine in dihydroergotoxine weeks (P = 0.001). The SCS-PD was 12.50 ± 2.84 and 9.25 ± 2.86 versus, respectively (P < 0.001). The response rate was 10% and 55%, respectively (P = 0.003). There were no significant adverse effects.

CONCLUSIONS

Dihydroergotoxine mesylate is safe and effective for sialorrhea in PD patients.

The increase in cyclic-AMP levels elicited by vasoactive intestinal peptide (VIP) in mouse cerebral cortical slices is potentiated by ergot alkaloids

We have recently observed that noradrenaline potentiates, via the activation of specific ?-receptors, the stimulatory effects of vasoactive intestinal peptide on cyclic-AMP levels. We report here that certain ergot derivatives of the ergopeptine class, such as bromocriptine, ergotamine and codergocrine known to interact with alpha-adrenergic receptors, will also potentiate the effects of VIP on cyclic-AMP levels, without increasing directly the levels of the cyclic nucleotide. To our knowledge, these results demonstrate for the first time the existence of an interaction between a neuropeptide and ergot alkaloids within the cerebral cortex.

Comparison of the efficacy and safety of daily dosages of 6 mg and 20 mg dihydroergocristine in the treatment of chronic cerebro-vascular disease

The efficacy and safety of two different regimens of dihydroergocristine, in the treatment of patients with chronic cerebro-vascular disease, were compared in this double-blind study. Forty out-patients, 11 males and 29 females, aged 55-80 years were randomly assigned to treatment with 6 or 20 mg dihydroergocristine, daily, for 3 months. The Sandoz Clinical Assessment for Geriatrics (SCAG) scale was used to assess the efficacy of treatment. Both doses induced a statistically significant improvement (P < 0.01) in total SCAG scores after both 45 and 90 days of treatment. The higher dose produced a significantly greater improvement in total SCAG scores than did the lower dose after both 45 and 90 days. There were no statistically or clinically significant changes in any of the laboratory parameters after either treatment; neither were there any statistically significant changes in blood-pressure or pulse-rate except in the case of standing systolic pressure which decreased significantly (P < 0.01) in the 20 mg group. The only adverse event reported was a case of mild gastric pain at the end of treatment with 20 mg dihydroergocristine.

Effects of chronic codergocrine mesylate administration on the brain somatostatinergic system in aged rats

Codergocrine mesylate (dihydroergotoxine; DHET), which is an ergot derivative, has been reported to counteract some age-induced impairments in brain function, but the mechanism of these effects is not known. We examined the effect of chronic DHET administration on the somatostatinergic system in the brains of aged rats. Intraperitoneal injections of DHET (1 mg/kg per day) or of vehicle were given to aged rats for 14 days, and resulted in a significant increase in somatostatin (SOM) receptor binding in all six brain regions examined except the hindbrain. DHET had no effect on SOM receptor binding in the brains of young-adult rats. However, the SOM concentration in aged rats was nearly identical to that in young-adult rats and the SOM concentration in different brain areas did not change after chronic administration of DHET. Thus, the present results suggest that chronic administration of DHET can ameliorate at least one of the age-induced impairments of brain somatostatinergic function.

Effects of dihydroergotoxine on some dopamine-related behaviors in rats

1. The effects of dihydroergotoxine on open-field behavior, apomorphine-induced stereotype and haloperidol-induced catalepsy were studied quantitatively in rats. 2. Dihydroergotoxine decreased the open-field behavior of rats, in a dose-dependent manner; this effect remained at least for 8 hr. 3. Dihydroergotoxine (10.0 mg/kg) caused a 1.40 leftward displacement of the dose-response curve constructed for apomorphine-induced stereotypy; the ED50 for apomorphine was reduced from 0.40 (+/- 0.05) to 0.29 (+/- 0.03). 4. Dihydroergotoxine (10.0 mg/kg) was unable to change haloperidol-induced catalepsy. 5. Results were discussed in the light of a possible interference of central noradrenergic systems with the expression of dopaminergic behaviors.

Dihydroergotoxine-induced bradycardia in rats

Dihydroergotoxine (0.01-0.3 mg kg-1 i.v.) decreased heart rate in pentobarbitone-anaesthetized rats. The bradycardia was reduced but not blocked by pre-treatment with guanethidine, yohimbine, propranolol or pithing. It was not prevented by bivagotomy, atropine, sulpiride or haloperidol. Dihydroergotoxine failed to affect, either the bradycardia produced by electrical stimulation of the vagus, or the cardioacceleration induced by i.v. isoprenaline. The increase in heart rate elicited in pithed rats by electrical stimulation of the spinal cord was reduced by dihydroergotoxine; this effect being inhibited by yohimbine but not by sulpiride. In conclusion, the main mechanism by which dihydroergotoxine (i.v.) induces bradycardia in the rat involves stimulation of alpha 2-adrenoceptors located predominantly at the cardiac sympathetic nerve endings.

Biochemical, behavioural, and endocrine effects of CK 204-933, a novel 8 beta-ergolene

CK 204-933 displaces [3H]dopamine and [3H]spiperone with high affinity from D-1 and D-2 recognition sites in membranes of calf caudate. Results from functional in vitro tests suggest that it is a partial agonist at D-1 receptors and an antagonist at D-2 receptors. These opposite effects at dopamine receptor subtypes are also expressed in vivo. For instance, in 6-hydroxydopamine lesioned rats, CK 204-933 induces contralateral rotations which are antagonised by SCH 23390 but not by sulpiride. On the other hand, CK 204-933 induces a long lasting increase of dopamine turnover in rat striatum and antagonises apomorphine-induced gnawing behaviour in rats. CK 204-933 increases prolactin serum levels in rats after subcutaneous administration, whereas after oral administration a moderate decrease of prolactin serum levels was seen. The latter effect is probably due to the formation of active metabolites. CK 204-933 exhibits also a high affinity to [3H]prazosin binding sites and antagonises serotonin-mediated stimulation of adenylate cyclase in rat hippocampus. On the other hand, CK 204-933 has no effect of only very weak effects on noradrenaline and serotonin release from rat cerebral cortex slices, which is consistent with its weak effects on noradrenaline- and serotonin-turnover in rat brain. Based on these properties it is suggested that CK 204-933 could be of therapeutic value in brain diseases associated with disturbances of monoaminergic neurotransmission.

Biochemical and pharmacological effects of fluperlapine on noradrenaline and acetylcholine systems in some rodent, bovine and crustacean preparations

Fluperlapine was compared with clozapine, chlorpromazine, haloperidol and imipramine regarding its effects on some cholinergic and noradrenergic animal systems. Fluperlapine and clozapine showed the most pronounced anticholinergic effects. Fluperlapine was equipotent with clozapine in displacing [3H]-QNB from muscarinic receptors of the calf cerebral cortex (IC50 about 15 nM). In the mydriasis test in the mouse and in the crayfish hindgut bioassay the differences between fluperlapine and clozapine were small. Like the other antischizophrenic drugs tested, fluperlapine displayed a marked affinity for alpha 1-adrenoceptors (calf cerebral cortex: IC50 about 10 nM) but a negligible affinity for alpha 2-adrenoceptors in the same tissue. Only clozapine showed a weak affinity for the latter receptor type. Fluperlapine was as effective as imipramine in antagonizing tetrabenazine-induced ptosis in the rat, the anti-ptotic effect remaining constant after up to ten daily drug administrations. Still, imipramine was stronger than fluperlapine as an inhibitor of the accumulation of [3H]-noradrenaline ([3H]-NA) in rat cerebral cortex slices. Fluperlapine's effects on the spontaneous and the electrically-induced release of [3H]-NA from rat cerebral cortex slices, with and without protriptyline, showed it to be an inhibitor of the reuptake of NA. The results indicate that the pharmacological profile of fluperlapine is similar to that of clozapine, with additional antidepressant properties.

Alpha-adrenergic agonist and antagonist activity of dihydroergotoxine in rats

The alpha-adrenergic activity of dihydroergotoxine had been studied in both pithed and urethane or pentobarbitone anaesthetized rats. In anaesthetized rats, blood pressure effects varied with the anaesthetic agent: hypotension with urethane, hypertension with pentobarbitone. This latter pressor response was a peripheral effect. In pithed rats, the vasopressor response to dihydroergotoxine was reduced competitively by yohimbine, and non-competitively by nifedipine, but not by prazosin or methysergide, showing that the vasoconstriction is mediated by alpha 2-adrenoceptors. Dihydroergotoxine decreases the tachycardia elicited by stimulation of the cardioaccelerator nerves, this effect being antagonized by yohimbine. It also reduced the pressor response to (-)-phenylephrine. These results indicated that, on the peripheral vascular system of the rat, dihydroergotoxine acts as an alpha 1-adrenoceptor blocker and an alpha 2-adrenoceptor agonist.

Neurochemical investigations in vitro with 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) in preparations of rat brain

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) in concentrations ranging from 10(-8) M to 10(-6) M induced a decrease, and at 10(-5) M an increase of both basal and electrically evoked tritium outflow from [3H]dopamine-prelabeled rat striatal slices. These effects of MPTP were almost abolished in the presence of nomifensine. Chromatographic separation of the released tritium compounds revealed that the decrease of tritium outflow was mostly due to a decrease in the outflow of the dopamine metabolite [3H]3,4-dihydroxyphenylacetic acid (DOPAC) and the increase of tritium outflow due to a massive release of [3H]dopamine. MPTP inhibited oxidative deamination of [3H]dopamine non-competitively in a crude mitochondrial preparation of rat brain, with an apparent Ki value of 4.5 microM. No relevant effect of MPTP on adenylate cyclase activity in homogenates and on basal and electrically evoked tritium outflow from [3H]choline-prelabeled slices of rat striatum could be detected. In contrast, MPTP facilitated both basal and electrically evoked tritium outflow from [3H]noradrenaline-prelabeled rat cerebral occipital cortex slices. Furthermore, MPTP counteracted the inhibitory effect of clonidine on evoked tritium outflow from rat cerebral occipital cortex slices. Moreover, in the presence of cocaine, the effect on basal, but not that on electrically evoked tritium outflow was attenuated. These results are compatible with the view that MPTP has no affinity to dopamine receptors but is preferentially taken up into dopaminergic nerve terminals by the nomifensine-sensitive uptake system where it reaches a concentration sufficient to inhibit intraneuronal monoamine oxidase (MAO). In contrast, the facilitatory effect of MPTP on evoked tritium outflow from [3H]noradrenaline prelabeled rat cerebral occipital cortex slices appears to result from antagonistic effects at presynaptic alpha 2-adrenoceptors. The observation that MPTP at lower concentrations (10(-8) to 10(-7) M) inhibits basal tritium outflow from rat cerebral occipital cortex slices suggests that this compound inhibits also intraneuronal deamination of noradrenaline by MAO in noradrenergic nerve terminals.