Microfluidic chambers used to test whether episodic breathing is regulated by the pons in turtle brainstems

Abstract

Our goal is to locate and characterize neurons controlling respiratory motor burst timing. Episodic breathing (clusters of fictive breaths separated by apneas) is expressed in isolated adult turtle brainstems and is regulated by serotonin 5‐HT3 receptor activation (decreases bursts/episode) and blockade (increases bursts/episode). To test whether pontine 5‐HT3 receptors regulate episodic breathing, microfluidic chambers constructed from silicone elastomer were used to apply drugs selectively to the pons. In time controls (n=2), baseline episodic discharge (1.9 bursts/episode) was unchanged after 2.0 h (1.8 bursts/episode). Application of a 5‐HT3 agonist to the pons (n=1) switched respiratory motor bursts from 1.5 bursts/episode (baseline) to singlet discharge (1.0 bursts/episode) within 5 min. 5‐HT3 antagonist application to the pons (n=1) increased baseline discharge from 1.0 to 1.4 bursts/episode after 40 min. These observations suggest that the pons plays an important role in regulating episodic breathing. Funded by NSF (IOB 0517302).