Autonomic and behavioural thermoregulation in starved rats

Abstract

We investigated the mechanism of starvation‐induced hypothermia in rats. Threshold core temperatures (Tcor) for tail skin vasodilatation and cold‐induced thermogenesis were determined after a 3 day starvation using a chronically implanted intravenous thermode. Food deprivation significantly lowered the threshold Tcor for heat production, but did not affect the heat loss threshold. Thermogenic response to a fall in Tcor below its threshold was enhanced by starvation. Preferred ambient temperatures (Tpref) and Tcor were measured before and during a 3 day starvation in a thermal gradient. The 3 day starvation significantly lowered Tcor only in the light phase of the day. The level of hypothermia was the same throughout the fasting period, while Tpref gradually increased during the 3 days of starvation. When rats were starved at a constant ambient temperature of 25°C (no thermal gradient), their Tcor levels were comparable with those of the rats kept in the thermal gradient. The results suggest that, in rats, hypothermia caused by starvation was not due to a decrement in thermogenic capability, but was due to a decrease in the threshold for the activation of thermogenesis.

Self-Starvation in the Rat: Running versus Eating

“…It is when a rat loses weight that the challenge begins. When given a choice of positions along a graded temperature space, the greater their loss of weight, the warmer the position a rat chooses (Sakurada et al, 2000). Thus, as a rat loses weight under ABA conditions in a cool laboratory, its core temperature is under increasing threat, but periods of vigorous running are followed by increases in body temperature (Hillebrand, de Rijke, Brakkee, Kas, & Adan, 2005).…”

Impact of malnutrition on immunity and infection

“…In the heart, it causes subclinical or even overt cardiac insufficiency that demands urgent correction. The loss of subcutaneous fat, which markedly reduces bodily capacity to regulate temperature and also to store water, can also occur, provoking dehydration, hypothermia and hypoglycemia (19)(20)(21). Moreover, PEM is associated with atrophy of the small intestine that triggers the loss of both absorption and digestion capacity (22,23).…”

Immune-to-brain signaling and central prostaglandin E2synthesis in fasted rats with altered lipopolysaccharide-induced fever

“…In a different study using fasted newborn rabbits, the depression of fever was reversed by allowing the animals to freely select warmer ambient temperatures in a thermal gradient (22), arguing that the selective attenuation of heat production, rather than the general downturn of thermoregulatory function, is the more likely mechanism responsible for the depression of fever during acute starvation. This selective ablation of metabolic thermogenesis coexisting with the preserved heat-seeking behavior resembles the thermoregulatory responses to starvation under noninflammatory conditions where food deprivation in laboratory animals rapidly induces depression of basal metabolic heat production and hypothermia, while increasing preference to higher ambient temperature, as a part of an adaptive strategy to conserve energy stores (47,58).…”