Effect of partial spinal cord ablation on exercise hyperpnea in ponies

Area of Science:

• Physiology
• Exercise Physiology
• Neuroscience

Background:

• Exercise hyperpnea, an increase in ventilation during physical activity, is crucial for maintaining blood gas homeostasis.
• The precise mechanisms, including the role of sensory feedback, driving exercise hyperpnea are still under investigation.
• Spinal afferent pathways are potential contributors to the complex regulation of respiratory responses to exercise.

Purpose of the Study:

• To investigate the contribution of spinal afferent information to exercise-induced changes in arterial PCO2 (PaCO2) during treadmill exercise in ponies.
• To determine if spinal deafferentation alters the normal hypocapnic response observed during exercise onset and steady-state.

Main Methods:

• Ten normal ponies were subjected to controlled treadmill exercise at varying workloads (low and moderate intensity).
• Arterial PCO2 was monitored throughout exercise.
• Seven ponies underwent bilateral spinal ablation (SA) of specific spinal tracts (dorsolateral sulcus and funiculus at L2) to assess the impact of deafferentation.

Main Results:

• In normal ponies, PaCO2 decreased significantly below resting levels during both exercise onset and steady-state across all workloads.
• Following spinal ablation (SA), the reduction in PaCO2 at exercise onset was attenuated at lower workloads.
• No significant differences in steady-state PaCO2 changes were observed between pre- and post-SA conditions, indicating a workload-dependent role for spinal afferents.

Conclusions:

• Spinal afferent information contributes to, but is not solely responsible for, the exercise hyperpnea response in ponies.
• The role of spinal afferents appears more pronounced during the initial phase of exercise and at lower intensities.
• Partial deafferentation suggests that the contribution of spinal afferent pathways to exercise hyperpnea may be underestimated in this study.