Intrapulmonary receptors in the Tegu lizard: II. Functional characteristics and localization;

Area of Science:

• Comparative physiology
• Respiratory system research
• Neurobiology

Background:

• Intrapulmonary receptors play a crucial role in respiratory control.
• Previous studies have characterized avian intrapulmonary receptors.

Purpose of the Study:

• To identify and characterize intrapulmonary receptors in the Tegu lizard.
• To compare the functional characteristics of Tegu lizard receptors with those in avian lungs.

Main Methods:

• Single-unit vagal recording in Tegu lizards.
• Stimulation of intrapulmonary receptors with CO2 and other agents.
• Electrical stimulation of the lung surface to elicit afferent activity.

Main Results:

• Identified CO2-sensitive receptors capable of following rapid CO2 fluctuations (up to 1.3 Hz).
• Observed no oxygen sensitivity in these receptors; halothane depressed their activity.
• Acetazolamide administration increased discharge frequency and abolished CO2 sensitivity, indicating non-molecular control.
• Receptors exhibited characteristics similar to avian intrapulmonary receptors.
• CO2 receptors had a broad receptive field (>1 cm2) with multiple receptors innervated by a single fiber.
• Mechanoreceptors had a localized receptive field and different conduction velocities.

Conclusions:

• Tegu lizard intrapulmonary receptors share functional similarities with avian counterparts.
• Receptor discharge is not directly controlled by the CO2 molecule itself.
• Distinct organization and properties exist for CO2 and mechanoreceptors in the Tegu lung.