Pharmacologic study of respiratory afterdischarge

Area of Science:

• Neuroscience
• Respiratory Physiology

Background:

• Respiratory afterdischarge is a poorly understood phenomenon involving prolonged respiratory output post-stimulation.
• The bulbopontine mechanism responsible for this afterdischarge remains anatomically and neurophysiologically uncharacterized.

Purpose of the Study:

• To investigate the potential role of major long-acting central neurotransmitters in generating respiratory afterdischarge.
• To determine if serotonin, dopamine, norepinephrine, or endorphins mediate this respiratory reflex.

Main Methods:

• Experiments were conducted on anesthetized, paralyzed, vagotomized, and glomectomized cats.
• Phrenic nerve activity was measured before, during, and after stimulation of the carotid sinus nerve and calf muscles.
• Animals were pretreated with specific antagonists for serotonin (methysergide, parachlorophenylalanine, 5,7-dihydroxytryptamine), dopamine-norepinephrine (alpha-methytyrosine, haloperidol), and endorphins (naloxone).

Main Results:

• Pretreatment with serotonin, dopamine-norepinephrine, or endorphin antagonists did not alter the response to stimulation.
• The magnitude of the respiratory afterdischarge was unaffected by the antagonist treatments.
• The time course of recovery for the respiratory afterdischarge remained unchanged across experimental groups.

Conclusions:

• The study concludes that the investigated central neurotransmitters (serotonin, dopamine, norepinephrine, endorphins) do not participate in the genesis of respiratory afterdischarge.
• The neurophysiological mechanisms underlying respiratory afterdischarge remain to be elucidated, independent of these major neurotransmitter systems.