Ascending pressor and depressor pathways in the cat spinal cord

Area of Science:

• Neuroscience
• Cardiovascular Physiology

Background:

• Understanding the neural control of blood pressure is crucial for managing cardiovascular diseases.
• The specific spinal pathways mediating pressor and depressor reflexes remain incompletely characterized.

Purpose of the Study:

• To investigate the localization of ascending spinal pathways controlling blood pressure.
• To differentiate the pathways responsible for pressor and depressor responses.

Main Methods:

• Anesthetized, vagotomized, and paralyzed cats were used.
• Stimulation of lumbar dorsal roots and cervical dorsolateral sulcus (DLS) with varying frequencies.
• Bilateral lesions in the DLS and dorsolateral funiculus (DLF) were performed.
• Neurophysiological recordings from the cervical sympathetic trunk.

Main Results:

• High-frequency stimulation of dorsal roots caused pressor responses, while low-frequency stimulation caused depressor responses.
• Lesions in the DLS abolished pressor responses, indicating its role in ascending pressor pathways.
• Lesions in the DLF abolished depressor responses, indicating its role in separate ascending depressor pathways.
• Both pathways were bilateral, with complete decussation within three spinal segments.

Conclusions:

• Ascending spinal pressor pathways are localized in the DLS.
• Ascending spinal depressor pathways are located in the DLF, separate from pressor pathways.
• Pressor pathways are optimally activated at high frequencies, whereas depressor pathways are optimally activated at low frequencies.