Cardiovascular changes during daily torpor in the laboratory mouse

Area of Science:

• Physiology
• Metabolic Regulation
• Cardiovascular Science

Background:

• Laboratory mice are facultative heterotherms, entering torpor during caloric restriction.
• Genetically modified mice are crucial for studying weight loss and caloric intake.
• Cardiovascular adaptations during fasting-induced torpor in mice require detailed investigation.

Purpose of the Study:

• To document the cardiovascular changes in mice during fasting-induced torpor.
• To investigate the relationship between core body temperature and heart rate during torpor.
• To assess blood pressure and peripheral resistance adjustments during torpor.

Main Methods:

• C57BL/6 mice were implanted with EKG/temperature or blood pressure telemeters.
• Mice were subjected to fasting and an ambient temperature of 19°C to induce torpor.
• Core body temperature, heart rate, and blood pressure were continuously monitored.

Main Results:

• Core body temperature dropped from 36.6°C to a minimum of 25.9°C during torpor.
• Heart rate decreased from 607 bpm to a minimum of 158 bpm, with a Q(10) of 2.61.
• Blood pressure (systolic, mean, diastolic) significantly decreased, with evidence of elevated total peripheral resistance.

Conclusions:

• Fasting-induced torpor in mice involves profound cardiovascular adjustments.
• Heart rate and blood pressure decrease significantly during torpor, paralleling the drop in core body temperature.
• Elevated total peripheral resistance is suggested during torpor in mice.