 The exact mechanism of the rhythm generation and transmission to motor nuclei remains controversial and the topic of much research.Several synthetic compounds have been shown to act on neurons specific to the preBötC, most being selective agonists or antagonists to receptor subtypes on neurons in the vicinity.Since many of these neurons express GABA, glutamate, serotonin and adenosine receptors, chemicals custom tailored to bind at these sites are most effective at altering respiratory rhythm.