Ret 3

Core body temperature was measured as described [42 (link)] using a thermocouple thermometer (MicroTherma 2T) with mouse rectal probe (RET-3), both from Braintree Scientific (Braintree, MA, USA), following the manufacturer’s instructions.

Numerous small molecules, including adenosine receptor agonist-like adenosine monophosphate and ⁶N-cyclohexyl adenosine, are known to induce reversible HMS (27 (link)–29 (link)). By using a drug repurposing approach in conjunction with cheminformatics, the in silico screening of many Food and Drug Administration-approved small molecules and drug-like molecules [LOPAC 1280, JHCCL(v2), Enzo FDA library] yielded a small molecule having adenosine receptor agonist action (hereafter referred to as SJNP-1). SJNP-1, clinically used for treating depression, was used in this study to induce HMS. HMS was induced 2 h after TBI by intraperitoneally (i.p.) administering 100 mg/kg body weight (b.w.) of SJNP-1 (Sigma–Aldrich, St. Louis, MO, USA) prepared in phosphate-buffered saline (PBS). Thereafter, the animals were kept in an incubator at 15°C (for maintaining HMS) for 6 h. They were then maintained at room temperature for recovery. The core body temperature (T_b) was manually measured on an hourly basis for the entire duration of the study (8 h) at different time points by using a rectal probe (RET 3, Braintree Scientific Inc., MA, USA).

Core body temperature was measured using a thermocouple thermometer (MicroTherma 2T) with a mouse rectal probe (RET-3), both from Braintree Scientific (Braintree, MA, USA), following the manufacturer’s instructions. For some experimental sets, mice were anesthetized by placing the animals in an anesthesia chamber, ventilated with 3% isoflurane in 100% oxygen at a flow rate of 1.5 L/min. Anesthesia was confirmed by the absence of the toe-pinch reflex. For a portion of the experiments, mouse cages were maintained at 34 °C by external warming of the cages using an electric heater.

Core body temperature was recorded before the conclusion of the frailty assessment with a glycerol-lubricated thermistor rectal probe (Braintree Scientific product# RET 3; measuring 3/4″ L0.028 dia.0.065 tip) inserted ∼ 2 cm into the rectum of a manually restrained mouse for approximately 10 s. The temperature was recorded to the nearest 0.1°C (Braintree Scientific product# TH5 Thermalert digital thermometer). Reductions in core body temperature are typical with aging and inversely correlate with frailty score, indicating morbidity. Increases in body temperature relative to controls may indicate hyperthermic responses induced by stress or inflammation.

Core body temperature was recorded just prior to the conclusion of the frailty assessment via a glycerol lubricated thermistor rectal probe (Braintree Scientific product# RET 3; measuring 3/4" L 0.028 dia. 0.065 tip) inserted ~2 cm into the rectum of a manually restrained mouse for approximately 10 s. The temperature was recorded to the nearest 0.1°C (Braintree Scientific product#TH5 Thermalert digital thermometer).