Core temperature circadian rhythm across aging in Spontaneously Hypertensive Rats

Area of Science:

• Physiology
• Chronobiology
• Animal Models

Background:

• Thermoregulation is crucial for physiological homeostasis.
• Aging and hypertension can impact circadian rhythms.
• Spontaneously Hypertensive Rats (SHR) are a common model for hypertension research.

Purpose of the Study:

• To investigate the circadian rhythm of core body temperature (Tcore) in aging Spontaneously Hypertensive Rats (SHR).
• To compare the Tcore circadian rhythm of SHR with normotensive Wistar (WIS) and Wistar Kyoto (WKY) rats across different age groups.
• To assess the suitability of WIS and WKY rats as control groups for SHR in thermoregulation studies.

Main Methods:

• Three rat strains (WIS, WKY, SHR) were divided into three age groups (16, 48, 72 weeks).
• Core body temperature (Tcore) circadian rhythms were monitored for three days using telemetry.
• Data were analyzed using the cosinor method to assess rhythm parameters like acrophase and amplitude.

Main Results:

• Young SHR (16 weeks) displayed higher Tcore during the activity phase compared to age-matched WIS and WKY rats.
• Both normotensive groups showed increased Tcore with aging.
• Amplitude of Tcore rhythm decreased with age in SHR, while acrophase remained consistent across strains and ages.

Conclusions:

• SHR exhibit impaired thermoregulatory control as early as 16 weeks of age.
• Circadian rhythm parameters of Tcore do not significantly differ across aging in these rat strains.
• WIS and WKY rats are validated as appropriate normotensive control strains for SHR in studies involving thermoregulation and aging.