Relation between yawning behavior and central serotonergic neuronal system in rats

Area of Science:

• Neuroscience
• Pharmacology
• Behavioral Science

Background:

• Yawning is a complex behavior with poorly understood neurobiological underpinnings.
• Dopaminergic and cholinergic systems are implicated in yawning, but the role of serotonergic pathways remains less clear.

Purpose of the Study:

• To investigate the role of central serotonergic pathways in modulating drug-induced yawning in rats.
• To compare the effects of apomorphine and physostigmine on yawning and their interaction with serotonin.

Main Methods:

• Subcutaneous administration of apomorphine and physostigmine to rats to elicit yawning.
• Modulation of yawning by administering 5-hydroxytryptophan (5-HTP), p-chlorophenylalanine (p-CPA), and 5,7-dihydroxytryptamine (5,7-DHT).
• Intrastriatal microinjections of apomorphine and physostigmine.

Main Results:

• Both apomorphine and physostigmine elicited dose-dependent yawning with bell-shaped dose-response curves.
• 5-HTP reduced yawning induced by both drugs, while p-CPA and 5,7-DHT differentially affected apomorphine-induced yawning.
• Intrastriatal apomorphine, but not physostigmine, elicited yawning, suggesting a differential role in the striatum.

Conclusions:

• Central serotonergic pathways significantly modulate drug-elicited yawning in rats.
• Apomorphine-induced yawning is more sensitive to serotonergic manipulation than physostigmine-induced yawning.
• These findings highlight the complex interplay between neurotransmitter systems in regulating yawning behavior.