Abstract:
Ergot alkaloids possess a wide and divergent spectrum of central and peripheral pharmacodynamic actions. They interfere with different receptor sites to stimulate and/or inhibit effector structures. The concept of partial agonism on alpha-adrenoreceptors has replaced the ancient hypothesis of direct stimulation of vascular and uterine smooth muscle. The mechanisms which are considered to be relevant for the therapeutic use of dihydroergotamine, a potent drug increasing venous tone, and of bromocriptine, a specific inhibitor of prolactin secretion, are discussed in more detail.
More Related Videos
Related Concept Videos
Direct-Acting Cholinergic Agonists: Pharmacokinetics
Direct-Acting Cholinergic Agonists: Chemistry and Structure-Activity Relationship
The direct-acting...
Drugs Affecting Neurotransmitter Release or Uptake
Drugs Acting on Autonomic Ganglia: Stimulants
Ganglionic stimulants activate NM nicotinic receptors in autonomic ganglia, falling into two categories: nicotine mimetics [e.g., lobeline, dimethylpiperazine, tetramethylammonium] and muscarinic receptor agonists [e.g., muscarine, methacholine]. The first category's action is rapid and blocked by nicotinic receptor antagonists, while the second category's action is delayed and blocked by atropine-like agents. Nicotine, an alkaloid, affects the heart rate by stimulating...
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...
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...


