Actions of co-dergocrine mesylate and its components at vascular smooth muscle

Evaluation of bromocriptine and plumbagin against the monogenean Rhabdosynochus viridisi: Computational drug repositioning and in vitro approaches

Monogeneans are parasitic platyhelminths that can harm the health of farmed fish. Few treatments are available against monogeneans, and the incentive to develop new antiparasitic agents is similar or even lower than the incentive for neglected parasitic diseases in humans. Considering that searching for and developing new antimonogenean compounds may require enormous investments of time, money, and animal sacrifice, the use of a computer-guided drug repositioning approach is a reasonable alternative. Under this context, this study aimed to evaluate the effectiveness of plumbagin and bromocriptine against adults and eggs of the monogenean Rhabdosynochus viridisi (Diplectanidae). Plumbagin is a phytochemical compound that has recently emerged as a potent antimonogenean; however, further investigation is required to determine its effects on different monogenean species. Bromocriptine was selected through a computational approach that included molecular docking analyses of 77 receptors of monogeneans (putative drug targets) and 77 ligands (putative inhibitors). In vitro experiments showed that bromocriptine does not exhibit mortality at concentrations of 0.1, 1, and 10 mg/L whereas plumbagin at 2 and 10 mg/L caused 100% monogenean mortality after 3 h and 30 min, respectively. The most effective concentration of plumbagin (10 mg/L) did not completely inhibit egg hatching. These findings underscore plumbagin as a highly effective agent against adult monogeneans and highlight the need for research to evaluate its effect(s) on fish. Although computational drug repositioning is useful for selecting candidates for experimental testing, it does not guarantee success due to the complexity of biological interactions, as observed here with bromocriptine. Therefore, it is crucial to examine the various compounds proposed by this method.

Indole-containing pharmaceuticals: targets, pharmacological activities, and SAR studies

Indole is a prestigious heterocyclic skeleton widely found in both naturally-occurring and biologically-active compounds. Pharmaceutical agents containing an indole skeleton in their framework possess a wide range of pharmacological properties, including antiviral, antitumor, analgesic, and other therapeutic activities, and many indole-containing drugs have been proven to have excellent pharmacokinetic and pharmacological effects. Over the past few decades, the FDA has approved over 40 indole-containing drugs for the treatment of various clinical conditions, and the development of indole-related drugs has attracted significant attention from medicinal chemists. This review aims to provide an overview of all the approved drugs that contain an indole nucleus, focusing on their targets, pharmacological activities, and SAR studies.

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.

Effect of co-dergocrine in the autoperfused superior mesenteric vascular bed of the rat

1. The influence of local administration of co-dergocrine in the in situ, constant flow autoperfused, superior mesenteric vascular bed of the rat was investigated. 2. Local infusion of co-dergocrine (0.1 micrograms kg-1 min-1) reduced the pressor response to electrical stimulation of the periarterial sympathetic nerves for the whole frequency range studied during cumulative frequency-response curves (1-8 Hz). 3. Co-dergocrine (0.01, 0.03, 0.1 micrograms kg-1 min-1) dose-dependently inhibited the pressor response to electrical stimulation at 4 Hz; increases in perfusion pressure produced by locally administered noradrenaline were inhibited to the same degree. 4. Pressor responses induced by locally administered phenylephrine were also inhibited by co-dergocrine (0.1 micrograms kg-1 min-1) while those produced by local injection of angiotensin II were not. 5. Local administration of the DA1-/DA2-receptor antagonist haloperidol (1 microgram kg-1), the DA2-receptor antagonist domperidone (10 micrograms kg-1) and the alpha 2-adrenoceptor antagonist rauwolscine (100 micrograms kg-1) partially prevented the influence of co-dergocrine on the electrically induced response. 6. The results show that the effect of co-dergocrine in the rat superior mesenteric vascular bed cannot simply be ascribed to interaction with the presynaptic inhibitory DA2-receptors on the noradrenergic nerve endings; it also has an antagonistic action at the postsynaptic alpha 1-adrenoceptors and an agonist action at the presynaptic alpha 2-adrenoceptors.

Venoconstrictor responses to dihydroergocristine and dihydroergotamine: evidence for the involvement of 5-HT1 like receptors

Dihydroergocristine (DHEC) and dihydroergotamine (DHE) were investigated on canine saphenous veins in vivo and on canine saphenous veins and basilar arteries in vitro. Following local i.v. infusion in vivo, the venoconstrictor response to DHEC was about 30% weaker than that produced by DHE. When administered orally, however, both ergot alkaloids elicited similar venoconstrictor effects. In vitro maximal contractile responses to DHEC and DHE of basilar arteries were only 20-30% of those produced by 5-HT, whereas in saphenous veins both DHEC and DHE elicited similar maximal effects as those observed with 5-HT. In saphenous veins, methiothepin antagonized venoconstrictor responses to 5-HT, DHEC, and DHE within the same concentration range, being significantly less potent when tested against noradrenaline. The reverse was true for yohimbine, which was significantly more potent against noradrenaline than against 5-HT, DHEC, and DHE. It is suggested that the venoconstrictor responses to both DHEC and DHE are mediated through 5-HT1-like receptors.

Is stimulation of prejunctional dopamine receptors an antihypertensive principle?

Bromocriptine and co-dergocrine (Hydergine R) reduce blood pressure and heart rate in experimental animals largely by stimulating DA2 receptors. A stimulant effect on DA1 receptors can be demonstrated in isolated tissues, but this action does not appear to make an important contribution to the depressor response to the two compounds, since effects are abolished by DA2 receptor blockade. Although both compounds are known to penetrate the brain, their antihypertensive effects, and the concomitant reductions in plasma noradrenaline levels produced in hypertensive patients can be prevented by domperidone, confirming a peripheral site of action. A review of the data available concerning the cardiovascular effects of bromocriptine and co-dergocrine in animals and man suggests that a DA2 receptor stimulant is effective in the treatment of hypertension.

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.

2-[125Iodo]LSD, a new ligand for the characterisation and localisation of 5-HT2 receptors

LSD was iodinated with Na125I and chloramine T, to get the radioligand [125I]LSD ( 125IOL ) and with N-I-succinimide to obtain the nonradioactive compound 2-I-LSD (IOL) for comparative pharmacological studies. The introduction of iodine in position 2 of LSD leads to an increase in selectivity for 5HT2 receptors. In rat cortex membranes, 125IOL possesses a KD = 0.9 +/- 0.1 nmol/l, Bmax = 240 +/- 20 fmoles/mg, and a nonspecific binding of 30-40% in presence of 100 nmol/l ketanserin. In competition experiments, 5HT antagonists showed monophasic displacement curves. Their KI-values correlate well with pD'2-values for inhibition of 5HT-induced contraction of canine basilar artery. It can be concluded that the sites labelled by 125IOL have pharmacological properties in common with central 5HT2 receptors, which are identical with vascular postjunctional 5HT receptors. The high specific radioactivity of 125IOL permits detection of even small 5HT2 receptor densities which exist in the guinea pig ileum. These 125IOL binding sites are pharmacologically different to those found in the brain or on the vessels and might be a special subpopulation of 5HT2 sites. For example, ketanserin has a high affinity to the sites labelled by 125IOL in the brain and a 100 times lower affinity to the sites labelled in the ileum. In a routine binding screen with various ligands, the inhibition constants of IOL for alpha 1, alpha 2, beta, histamine and muscarinic receptors are greater than 100 nmol/l with the exception for dopamine receptors, 40 nmol/l. 125IOL was employed for the autoradiographic localisation of its binding sites after in vitro labelling of microtome rat brain sections. 125IOL labelled 5HT2 sites in the cortex and dopamine receptors in the nucleus caudatus. The exposure times required were very short, compared to those of other 5HT2 ligands available.

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

Co-dergocrine (Hydergine), composed of four dihydrogenated peptide ergot alkaloids (dihydroergocornine, dihydroergocristine, dihydro-alpha-ergokryptine and dihydro-beta-ergokryptine), has been reported to interact with alpha-adrenoceptors. The effect of the combination and its individual components on alpha-adrenoceptors subtypes in the rat brain was investigated in the present study. All five ergot drugs displaced [3H]rauwolscine, [3H]clonidine and [3H]WB 4101 from specific binding sites in membrane preparations from rat and bovine brain at nanomolar concentrations. In rat cerebral occipital cortex slices, the ergot drugs inhibited 1-noradrenaline-stimulated cyclic AMP formation (alpha 1-adrenoceptor test) and facilitated electrically evoked noradrenaline release (alpha 2-adrenoceptor test) at nanomolar concentrations. The results from the functional tests suggest that the ergot drugs have a slightly higher affinity to alpha 2-adrenoceptors which are antagonised in a competitive manner. The alpha 1-adrenoceptors are antagonised by the ergot drugs in a non-competitive manner. The relative order of potency at both receptor types was similar in that dihydroergocornine, dihydro-alpha-ergokryptine and dihydro-beta-ergokryptine were equipotent, whereas dihydroergocristine was less potent. The effect of the combination of the ergot alkaloids at both alpha-adrenoceptors appears to reflect the summation of the contributions of its components. The differences seen in the functional tests were less pronounced in the binding tests.

Evidence for common pharmacological properties of [3H]5-hydroxytryptamine binding sites, presynaptic 5-hydroxytryptamine autoreceptors in CNS and inhibitory presynaptic 5-hydroxytryptamine receptors on sympathetic nerves

The affinities of 16 5-hydroxytryptamine (5-HT) receptor agonists (indole derivatives) and 7 5-HT receptor antagonists for [3H]5-hydroxytryptamine [( 3H]5-HT) binding sites in rat cerebral cortex membranes were determined. In addition, the potencies of the agonists for inhibiting the electrically induced tritium overflow from rat brain cortex slices preincubated with [3H]5-HT and from canine saphenous veins preincubated with [3H]noradrenaline were measured. Furthermore, the potencies of the indole derivatives for inducing contractile responses of canine saphenous veins were recorded. In addition, the interaction of the antagonists with unlabelled 5-HT at the 5-HT autoreceptor was studied in rat brain cortex slices. There was a good correlation between the binding affinities of the indole derivatives for the [3H]5-HT sites of rat brain cortex membranes and their potencies for inhibiting the evoked tritium overflow from both rat brain cortex slices and strips of canine saphenous vein. Comparison of the inhibition constants derived from the overflow experiments in both tissues again revealed a high correlation coefficient while there was only weak correlation between the binding affinities in rat brain cortex and the contractile potencies of the drugs in canine saphenous vein strips. When 5-HT receptor antagonists were investigated, metitepin and metergoline showed moderate affinities for the 5-HT autoreceptors in rat brain cortex slices, whereas quipazine had only weak affinity, and ketanserin, metoclopramide, cinanserin and cyproheptadine exhibited no antagonistic property. In binding experiments, the competition curves of most 5-HT receptor antagonists were biphasic, suggesting that the [3H]5-HT binding sites are heterogeneous.(ABSTRACT TRUNCATED AT 250 WORDS)