Evidence for different pharmacological targets for imidazoline compounds inhibiting settlement of the barnacleBalanus improvisus

Abstract

We describe the effect of eight different imidazoline/guanidinium compounds on the settlement and metamorphosis of larvae of the barnacle Balanus improvisus. These agents were chosen on the basis of their similar pharmacological classification in vertebrates and their chemical similarity to medetomidine and clonidine, previously described as highly potent settlement inhibitors (nanomolar range). Seven of the tested compounds were found to inhibit settlement in a dose-dependent manner in concentrations ranging from 100 nM to 10 microM without any significant lethal effects. In vertebrate systems these substances have overlapping functions and interact with both alpha-adrenoceptors as well as imidazoline binding sites. Antagonizing experiments using the highly specific alpha(2)-antagonist methoxy-idazoxan or agmatine (the putative endogenous ligand at imidazoline receptors) were performed to discriminate between putative pharmacological mechanisms involved in the inhibition of cyprid settlement. Agmatine was not able to reverse the effect of any of the tested compounds. However, methoxy-idazoxan almost completely abolished the settlement inhibition mediated by guanabenz (alpha(2)-agonist, I(2) ligand), moxonidine (alpha(2)-agonist, I(1) ligand) and tetrahydrozoline (alpha-agonist, I(2) ligand). The actions of cirazoline (alpha(1)-agonist, I(2) ligand) BU 224 (I(2) ligand) and metrazoline (I(2) ligand) were not reversed by treatment with methoxy-idazoxan. These results suggest that the settlement inhibition evoked by the I(2) ligands and alpha(2)-agonists used in this study of the neurologically simple but well-organized barnacle larva is mediated through different physiological targets important in the overall settlement process.

Activated fly ash catalyzed facile synthesis of novel spiro imidazolidine derivatives as potential antibacterial and antifungal agents

“…The present study describes the use of 6-carbethoxy-3,5-diarylcyclohex-2-enone 23 as a key intermediate with three versative functional groups i.e., ketone, olefin, and ester for the synthesis of imidazolidine derivatives. Owing to our interest in synthesis of fascinating biologically active hybrid heterocyclic compounds [24][25][26] and as part of our research program, herein we planned to design a spiro imidazolidine derivatives bearing a cyclohexene substituent on the carbon between the nitrogen centers to give a new series of spiro imidazolidine heterocycles because most bio-active imidazolidine derivatives bear a substituent (aryl or alkyl group) on the carbon between the nitrogen centers [18][19][20][21] .…”

“…Xylometazoline is a drug which is used as a nasal decongestant. Tetrahydrozoline, a derivative of imidazolidine, is an α-agonist 19 and its main mechanism of action is the constriction of conjunctival blood vessels. This serves to relieve the redness of the eye caused by minor ocular irritants.…”

New Directions in Antifouling Technology

“…These include capsaicin and zosteric acid [47][48][49], tannins [18], tannin-aluminium complexes [50] and cupric tannate [51]. Synthetic analogues of naturally occurring antifoulants have also been found to deter fouling [52,53].…”

Antifouling Compounds

“…8 for chemical structures and full chemical names) are promiscuous and interact with both α-adrenergic receptors and imidazoline (I 1 and I 2 ) binding sites (Ernsberger 1999). Therefore, we recently conducted a further characterization of imidazoline binding site ligands, as well as α-adrenoceptor agonists, in a cyprid settlement assay (Dahlström et al 2005). The compounds examined were chosen on the basis of their similar pharmacological classification in vertebrates and for their chemical similarities to medetomidine and clonidine (Fig.…”