Serotonin regulates rhythmic whisking

Area of Science:

• Neuroscience
• Animal Behavior
• Sensory Systems

Background:

• Rodents use rhythmic whisker movements, known as whisking (5-9 Hz), for environmental exploration.
• The neural circuitry, specifically a brainstem central pattern generator (CPG), regulating whisking remains largely unknown.

Purpose of the Study:

• To investigate the role of serotonin (5-HT) inputs to whisking facial motoneurons (wFMNs) as part of the whisking CPG.
• To determine if serotonin is necessary and sufficient for generating rhythmic whisker movements.

Main Methods:

• In vitro electrophysiological recordings of wFMNs in response to serotonin.
• Application of selective serotonin receptor antagonists (5-HT2, 5-HT3) in vitro and in vivo.
• In vivo stimulation of brainstem serotonergic raphe nuclei.
• In vivo unilateral infusion of serotonin receptor antagonists to observe effects on whisking.

Main Results:

• Exogenous serotonin induced rhythmic firing in wFMNs at whisking frequencies in vitro.
• Selective 5-HT2 or 5-HT3 receptor antagonists suppressed this rhythmic firing.
• Stimulation of raphe nuclei evoked whisker movements in vivo.
• Antagonist infusion suppressed ipsilateral whisking and altered movement frequency and symmetry.

Conclusions:

• Serotonin is both necessary and sufficient for generating rhythmic whisker movements.
• Serotonergic premotoneurons are integral components of the whisking CPG.
• Serotonin signaling via 5-HT2 and 5-HT3 receptors is crucial for whisking motor control.