Unbalanced thermoregulation in experimental autoimmune encephalitis induced in Lewis rats

Abstract

Thermoregulation in patients suffering from multiple sclerosis (MS) is impaired and may result in either increases or decreases in body temperature. We have found that rat experimental autoimmune encephalitis (EAE), being a model of MS, is associated with body temperature disturbances as well. The purpose of the current study was to examine whether the altered body temperature in EAE-induced rats is due to either a deficit in thermoregulation or a controlled change in its set point. Subcutaneous injection of encephalitogenic emulsion into both pads of hind feet of the Lewis rats provoked EAE symptoms. Body temperature (Tb) of 6 rats was measured using biotelemetry system, and ambient temperature (Ta) preferred by 6 rats of another group was analyzed using thermal gradient system. Symptoms of EAE started 11 days postinjection and progressed quickly, culminating in a complete paralysis in rats placed in the gradient, which was associated with behavioural fever (accordingly, selected Ta raised to as much as 32.8 ± 0.5 °C vs 27.2 ± 0.6 °C in control rats). On the other hand, EAE rats, placed at a constant Ta of 24 °C, were able to generate fever (Tb of 37.8 ± 0.1 °C) at the start of the illness and then paralysis compromised fever (most likely due to an impairment of thermogenesis), which, surprisingly, resulted in recovery. We conclude that EAE onset in rats is associated with fever and its behavioural supporting leads to aggravation of the autoimmune neurotoxicity.

Keywords: Body temperature (Tb); Experimental autoimmune encephalitis (EAE); Multiple sclerosis; Preferred ambient temperature (Ta); Setpoint; Thermal gradient.