A brain stem circuit integrating reflexive and anticipatory salivation

Area of Science:

• Neuroscience
• Autonomic Nervous System Regulation
• Salivary Gland Function

Background:

• Salivation is crucial for oral health, taste, swallowing, and digestion.
• The precise neural mechanisms governing salivation are not fully understood.
• Identifying the brain's salivatory control center is a key research gap.

Purpose of the Study:

• To identify and characterize the central neural circuits regulating salivation.
• To investigate the integration of sensory and learned anticipatory signals in salivation control.
• To elucidate the role of the inferior salivatory nucleus (IS) in salivation.

Main Methods:

• Optogenetic activation of choline acetyltransferase-expressing neurons in the mouse brain stem.
• Fiber photometry to monitor real-time neural activity in the IS.
• Electrophysiological recordings and behavioral assays, including Pavlovian conditioning.

Main Results:

• Activation of IS neurons expressing choline acetyltransferase is sufficient to induce salivation.
• IS neural activity directly correlates with salivatory output during sensory stimulation.
• The gustatory cortex provides input to the IS, essential for anticipatory salivation in response to predictive cues.

Conclusions:

• A salivatory center in the mouse brain stem, specifically the IS, has been identified.
• This center integrates direct sensory input and learned anticipatory signals for salivation control.
• These findings establish a neural circuit for taste-evoked and anticipatory salivation, offering insights into autonomic function in health and disease.