Dopaminergic modulation on respiratory rhythm in rat brainstem-spinal cord preparation.

Dopamine (DA) is known to regulate both higher order and autonomic brain functions. To elucidate the effects of DA on respiratory rhythm generation, isolated brainstem-spinal cord was treated with DA and each DA receptor agonist individually. DA application facilitated respiratory rhythm in pons-medulla-spinal cord preparations, but depressed it in medulla-spinal cord preparations. Furthermore, we found that DA application depressed Pre-Inspiratory (Pre-I) neurons but not Inspiratory or Expiratory neurons and that among the various DA receptor agonists, only a D4 agonist, PD168077, depressed respiratory rhythm. Therefore, the primary target of DA action in modulating respiratory rhythm generation is the Pre-I neurons in the medulla.