Respiratory Rhythm Generation and Plasticity

Breathing is a rhythmic motor behavior produced throughout our entire lifetime, but how neurons in the brainstem generate this behavior is not known. We study isolated brainstems from hypoxia-resistant red-eared slider turtles because the brainstems produce expiratory and inspiratory activity for days under in vitro conditions. Currently, we are testing whether pacemaker neurons play a critical role in rhythm generation using multichannel recordings with silicon microelectrodes. Our major findings are that pacemaker neurons may not be required for respiratory rhythm generation.

Also, bath application of serotonergic and adrenergic drugs produces acute and long-lasting (plasticity) in the timing and clustering of respiratory-related bursting activity. Our major findings are that activation of 5-HT3 and alpha-1 adrenergic receptors increases respiratory burst frequency and reduces episodic breathing.

In addition to studies on isolated turtle brainstems, we are also characterizing how different drugs (e.g., opioids) alter breathing pattern in freely-swimming turtles. Our major findings are that mu-opioid receptor activation causes respiratory depression by decreasing breathing frequency.

 

Figure 1 from recent paper (Johnson, Wiegel, Majewski, 2007):

Figure 5 from recent paper (Johnson, Wiegel, Majewski, 2007):