Related Experiment Video
Updated: Aug 18, 2026

Quantifying Agonist Activity at G Protein-coupled Receptors
Published on: December 26, 2011
Agonism at 5-HT2B receptors is not a class effect of the ergolines
Sven Jähnichen1, Reinhard Horowski, Heinz H Pertz
1Free University of Berlin, Institute of Pharmacy, Königin-Luise-Str. 2+4, 14195 Berlin, Germany.
Abstract:
Restrictive cardiac valvulopathies observed in Parkinson patients treated with the ergoline dopamine agonist pergolide have recently been associated with the agonist efficacy of the drug at 5-hydroxytryptamine2B (5-HT2B) receptors. To evaluate whether agonism at 5-HT2B receptors is a phenomenon of the class of the ergolines, we studied 5-HT2B receptor-mediated relaxation in porcine pulmonary arteries to five ergolines which are used as antiparkinsonian drugs. Pergolide and cabergoline were potent full agonists in this tissue (pEC50 8.42 and 8.72). Bromocriptine acted as a partial agonist (pEC50 6.86). Lisuride and terguride, however, failed to relax the arteries but potently antagonized 5-HT-induced relaxation (pKB 10.32 and 8.49). Thus, agonism at 5-HT2B receptors seems not to be a class effect of the ergolines.
Related Concept Videos
Adrenergic Agonists: Chemistry and Structure-Activity Relationship
Aromatic ring substitutions: Substituting the aromatic ring with –OH groups at positions 3 and 4 yields catecholamines (e.g., epinephrine), which have a high affinity for adrenoceptors. Hydrogen bonding between –OH groups and receptors enhances adrenergic activity.
Separation of the aromatic...
Adrenergic Agonists: Direct-Acting Agents
These agents can be classified...
Adrenergic Agonists: Therapeutic Classification
Vasopressor or pressor agents: They increase blood pressure and function as cardiac stimulants. Examples include endogenous catecholamines (norepinephrine and dopamine) and synthetic agents (phenylephrine).
Bronchodilators: β2-agonists can relax bronchial muscles and widen airways. They are commonly used for treating obstructive pulmonary...
Adrenergic Agonists: Indirect-Acting Agents
One mechanism involves depleting stored catecholamines by displacing them from synaptic vesicles. These agents, known as "displacers," are transported into vesicles at the expense of noradrenaline. Examples include amphetamine and tyramine, which lack a catechol moiety, resulting in prolonged action, improved oral bioavailability, and...
Direct-Acting Cholinergic Agonists: Chemistry and Structure-Activity Relationship
The direct-acting...
Adrenergic Antagonists: Chemistry and Classification of ɑ-Receptor Blockers
Nonselective α-blockers: Nonselective α-blockers contain haloalkylamine or imidazoline moieties. Phenoxybenzamine, with a haloalkylamine...

