Cerebrospinal fluid [Ca2+] and rectal temperature response during exercise in dogs

Area of Science:

• Physiology
• Neuroscience
• Animal Science

Background:

• Thermoregulation is crucial for maintaining homeostasis during physical activity.
• Cerebrospinal fluid (CSF) composition can influence central nervous system functions, including temperature regulation.
• The role of calcium ions (Ca2+) in CSF on thermoregulation during exercise is not fully understood.

Purpose of the Study:

• To investigate the effect of normocalcemic and hypercalcemic artificial cerebrospinal fluid infusions into the canine cerebral ventricle on rectal temperature during rest and exercise.
• To determine if elevated CSF calcium levels alter thermoregulatory responses and heat loss during physical exertion.

Main Methods:

• Rectal temperature (Tre) was measured in five dogs at rest and during treadmill exercise.
• Artificial cerebrospinal fluids with normocalcic (1.3 mM Ca2+) and hypercalcic (2.6 mM Ca2+) concentrations were infused into the left lateral cerebral ventricle.
• Body weight loss was monitored as an indicator of heat loss during exercise.

Main Results:

• Neither normocalcemic nor hypercalcemic CSF infusions affected resting rectal temperature.
• During exercise, hypercalcemic CSF infusion resulted in a significantly smaller rise in rectal temperature compared to normocalcemic infusion and no infusion (P < 0.01).
• Mean body weight loss during exercise was greater with hypercalcic infusion, indicating increased heat loss.

Conclusions:

• Elevated calcium ion concentrations in the cerebrospinal fluid reduce the exercise-induced increase in rectal temperature in dogs.
• These findings suggest that Ca2+ ions modulate the sensitivity of central thermoreceptors to thermal stimuli.
• Increased heat loss during physical exercise may be a consequence of altered central thermoregulation in response to hypercalcemia in CSF.