Choline evokes fluid secretion by perfused rat mandibular gland without desensitization

Area of Science:

• Pharmacology
• Physiology

Background:

• Choline's secretomotor action on salivary glands is not fully understood.
• Acetylcholine is a known secretomotor agonist, but can cause tachyphylaxis.

Purpose of the Study:

• To investigate the secretomotor action of choline on rat mandibular gland secretion.
• To compare choline's effects with acetylcholine, particularly regarding tachyphylaxis.

Main Methods:

• Isolated perfused rat mandibular gland model.
• Administration of varying concentrations of choline and acetylcholine.
• Use of antagonists like atropine, propranolol, and phentolamine.

Main Results:

• Choline effectively stimulated salivary secretion, comparable to acetylcholine.
• Choline did not induce tachyphylaxis until concentrations exceeded 80 mM, unlike acetylcholine.
• Choline's action was blocked by atropine, indicating muscarinic receptor involvement.
• Acetylcholine addition always induced tachyphylaxis, even during choline stimulation.

Conclusions:

• Choline and acetylcholine likely act on the same muscarinic receptors.
• Choline's lack of tachyphylaxis at lower doses helps elucidate the phenomenon's causes.
• Excessive cytosolic free calcium buildup is the most probable cause of acetylcholine-induced tachyphylaxis.