Brainstem mechanisms controlling cardiovascular reflexes in channel catfish

Area of Science:

• Neuroscience
• Cardiovascular Physiology
• Fish Biology

Background:

• The general visceral nucleus (nGV) in fish is homologous to the mammalian nucleus tractus solitarius.
• Understanding central cardiovascular control mechanisms is crucial for comparative physiology.

Purpose of the Study:

• To identify central mechanisms controlling resting heart rate and blood pressure in catfish.
• To investigate the role of glutamatergic receptors in cardiovascular responses to hypoxia.

Main Methods:

• Microinjections of kynurenic acid (glutamate receptor antagonist) and kainic acid (glutamate receptor agonist) into the nGV of anesthetized catfish.
• Monitoring of heart rate and blood pressure under normoxic and hypoxic conditions.

Main Results:

• Kynurenic acid reduced resting heart rate but did not affect hypoxia-induced bradycardia.
• Kainic acid reduced resting heart rate and blocked hypoxia-induced bradycardia.
• Neither drug affected blood pressure during normoxia or hypoxia.

Conclusions:

• Glutamatergic receptors in the nGV play a role in maintaining resting heart rate in catfish.
• These receptors are essential for the bradycardia response to aquatic hypoxia.