Related Experiment Video
Updated: Oct 3, 2026

Paradigms for Pharmacological Characterization of C. elegans Synaptic Transmission Mutants
Published on: August 18, 2008
[Effects of parasympathetic drugs on head-twitch response induced by tyramine (author's transl)]
Abstract:
We investigated the effects of various parasympathetic drugs on the head-twitch response (HTR), as induced by intracerebroventricular (i.c.v.) administration of tyramine in mice pretreated with safrazine, a monoamine oxidase inhibitor. Intraperitoneal administration of neostigmine, methacholine, carbamylcholine, methylatropine or hexamethonium did not alter the HTR induced by tyramine. The i.c.v. infusion of acetylcholine, physostigmine, nicotine, carbamylcholine or atropine slightly inhibited the tyramine-response. The i.c.v. infusion of pilocarpine, methacholine, mechamylamine, hexamethonium or tetraethylammonium resulted in a slight or significant potentiation of the HTR. These results suggest that the HTR induced by tyramine is accelerated by mechanisms related to muscarinic receptors within the central nervous system and that the tyramine-response is suppressed by mechanisms related to nicotinic receptors.
Related Concept Videos
Direct-Acting Cholinergic Agonists: Pharmacological Actions
Indirect-Acting Cholinergic Agonists: Pharmacological Actions
At the neuromuscular junction, these agents work by inhibiting the breakdown of acetylcholine, allowing it to remain bound to the receptor and bind to nearby receptors. This process leads to repetitive firing of the endplate, causing muscle...
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 sympathetic or...
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...
Drugs Affecting Neurotransmitter Release or Uptake
Drugs Affecting Neurotransmitter Synthesis

