Repetitive/rhythmic masticatory muscle activity under urethane anesthesia in guinea pigs: a descriptive pilot study

Area of Science:

• Neuroscience
• Sleep Science
• Animal Models

Background:

• Rhythmic/repetitive masticatory muscle activity can occur spontaneously during unconscious brain states.
• Understanding the mechanisms of such activity requires an appropriate experimental model.

Purpose of the Study:

• To investigate jaw movements and masticatory muscle activity during cyclic brain state alternations.
• To establish an experimental model for studying rhythmic jaw movements (RJMs) under urethane anesthesia.

Main Methods:

• Simultaneous recording of electroencephalography (EEG), electrocardiography, nasal airflow, jaw movements, and jaw muscle electromyography in urethane-anesthetized guinea pigs.
• Classification of cortical brain states into deactivated and activated states based on EEG delta power.
• Analysis of rhythmic jaw movements (RJMs) and associated physiological changes.

Main Results:

• Significant differences in cortical activity and physiological rates were observed between activated and deactivated brain states.
• The majority of rhythmic jaw movements (RJMs) occurred during the activated state and were associated with lateral jaw excursions and masseter muscle activation.
• RJMs were preceded by decreased EEG delta activity and transient increases in cardiac and respiratory activity.

Conclusions:

• Masticatory muscles exhibit repetitive, rhythmic activation during cyclic brain state alternations under urethane anesthesia.
• Urethane-anesthetized guinea pigs serve as a viable model for exploring the mechanisms of RJMs in unconscious states, including sleep bruxism.