Central cholinergic receptor supersensitivity after long-term atropine administration.

Area of Science:

• Neuroscience
• Pharmacology
• Behavioral Science

Background:

• Cholinergic system plays a crucial role in regulating various brain functions.
• Atropine (AT) is a muscarinic antagonist used to study cholinergic pathways.
• Understanding the long-term effects of cholinergic blockade is vital for therapeutic applications.

Purpose of the Study:

• To investigate the effects of acute and chronic atropine (AT) administration on central cholinergic receptor sensitivity.
• To examine behavioral responses to acetylcholine (ACh) following different AT treatment durations.
• To assess the impact of long-term AT treatment on oxotremorine-induced tremors in mice.

Main Methods:

• Rats received a single dose or daily doses of AT (5 mg/kg) for 14 or 31 days.
• Acetylcholine (ACh) was injected intracerebroventricularly to elicit behavioral responses.
• Oxotremorine-induced tremorogenic effects were measured in mice chronically treated with AT (10 mg/kg for 1 month).

Main Results:

• A single dose of AT antagonized ACh-induced behaviors.
• Chronic AT administration for 14 or 31 days enhanced ACh-induced depressive behaviors in rats.
• Long-term AT treatment in mice potentiated the tremorigenic effect of oxotremorine.

Conclusions:

• Acute blockade of central cholinergic receptors by AT transiently inhibits ACh effects.
• Prolonged blockade of central cholinergic receptors leads to receptor hypersensitivity.
• This hypersensitivity may underlie altered behavioral and physiological responses observed after chronic AT exposure.