Platelet-activating factor modulates cardiorespiratory responses in the conscious rat

Area of Science:

• Neuroscience
• Cardiorespiratory Physiology

Background:

• Platelet-activating factor receptor (PAFR) activation is linked to increased neuronal excitability.
• The role of Platelet-activating factor (PAF) in cardiorespiratory control remains largely unexplored.

Purpose of the Study:

• To investigate the role of PAF in cardiorespiratory regulation within the dorsocaudal brain stem of rats.
• To determine the impact of PAFR activation on ventilatory responses to normoxia and hypoxia.

Main Methods:

• Microinjections of a PAF analog (mc-PAF) or vehicle into the dorsocaudal brain stem of conscious, unrestrained adult rats.
• Assessment of ventilatory, cardiovascular, and blood gas parameters.
• Evaluation of the effects of a PAFR antagonist (BN-52021) and PAF acetyl hydrolase on these responses.
• Comparison of responses to hypercapnic (5% CO2) and hypoxic (10% O2) challenges with and without PAFR blockade.

Main Results:

• Microinjection of mc-PAF significantly increased minute ventilation (VE) primarily through tidal volume changes, accompanied by increased heart rate, respiratory alkalosis, and decreased arterial blood pressure.
• These effects were specific to active PAF analogs and were blocked by the PAFR antagonist BN-52021 or recombinant PAF acetyl hydrolase.
• PAFR antagonism did not affect hypercapnic ventilatory responses but significantly blunted the VE response to hypoxia.
• VE increased from 120.4 ± 7.5 to 204.6 ± 11.4 ml/min during hypoxia with vehicle, whereas it increased only from 118.7 ± 6.9 to 137.3 ± 8.9 ml/min after BN-52021.

Conclusions:

• PAFR activation in the dorsocaudal brain stem exerts significant cardioventilatory effects under normoxic conditions.
• PAFR plays a crucial modulatory role in the ventilatory response to hypoxia in conscious rats.