Body and brain temperature coupling: the critical role of cerebral blood flow

Abstract

Direct measurements of deep-brain and body-core temperature were performed on rats to determine the influence of cerebral blood flow (CBF) on brain temperature regulation under static and dynamic conditions. Static changes of CBF were achieved using different anesthetics (chloral hydrate, CH; α-chloralose, αCS; and isoflurane, IF) with αCS causing larger decreases in CBF than CH and IF; dynamic changes were achieved by inducing transient hypercapnia (5% CO2 in 40% O2 and 55% N2). Initial deep-brain/body-core temperature differentials were anesthetic-type dependent with the largest differential observed with rats under αCS anesthesia (ca. 2°C). Hypercapnia induction raised rat brain temperature under all three anesthesia regimes, but by different anesthetic-dependent amounts correlated with the initial differentials—αCS anesthesia resulted in the largest brain temperature increase (0.32 ± 0.08°C), while CH and IF anesthesia lead to smaller increases (0.12 ± 0.03 and 0.16 ± 0.05°C, respectively). The characteristic temperature transition time for the hypercapnia-induced temperature increase was 2–3 min under CH and IF anesthesia and ~4 min under αCS anesthesia. We conclude that both, the deep-brain/body-core temperature differential and the characteristic temperature transition time correlate with CBF: a lower CBF promotes higher deep-brain/body-core temperature differentials and, upon hypercapnia challenge, longer characteristic transition times to increased temperatures.

Acute cold stress and mild hypothermia impact on short-term, working memory and attention

“…Mäkinen et al (2006) observed that decreased skin temperatures and thermal sensations of cold were associated with longer response times and a decreased efficiency in the simple reaction time task which measures simple visuomotor response times. Also, our data agree with a recent Brazaitis et al (2014) study, where decrements in the reaction time were observed during the choice reaction task after intermittent immersion in bath water (14 °C).A series of studies raise the possibility that brain temperatures are somewhat independent from both core and oesophageal temperatures (Harris et al, 2008;Zhu et al, 2009). However, it is unknown how actually temperatures may differ across the brain regions and whether that pattern helps to account for the differential impact of cold exposure on different cognitive abilities.…”

PET Demonstrates Functional Recovery After Transplantation of Induced Pluripotent Stem Cells in a Rat Model of Cerebral Ischemic Injury

“…Briefly, after initial induction of anesthesia with a ketamine-xylazine mixture (a 60 mg/kg dose of ketamine plus a 10 mg/kg dose of xylazine, intraperitoneally) (24), the rat was shaved, transported to the surgery table in a dedicated surgery room, and fixed on the platform with a warm pad (model 69001; RWD Life Science) to maintain the body temperature throughout the procedure. The animal received an intraperitoneal injection of 10% chloral hydrate (350 mg/kg) (24). Focal brain ischemia was induced by the intraluminal suture technique.…”

Experimental Intracerebral Hemorrhage: Avoiding Pitfalls in Translational Research

“…Intraoperative parameters may include heart rate, blood pressure, temperature, blood gas analysis, electrocardiogram, and electroencephalogram activity. Some recommend the measurement of both rectal and cranial temperatures (Busto et al, 1989), although there has been excellent correlation between the two with isofluorane anesthetic (R 2 = 0.9996) (Zhu et al, 2009), suggesting that invasive brain temperature monitoring is unnecessary. The measurement of CBF can be used to monitor cerebral ischemia, seizures, and the effect of drugs on CBF; although, as earlier described, true ischemia is not thought to occur in ICH unless the hematoma is of significant size .…”