Chapter 38 - Temperature Regulation in Experimental Mammals and Humans Exposed to Organophosphate and Carbamate Agents

Abstract

The chapter reviews the effects of anti-ChE agents on the thermoregulatory system of mammals and humans, including studies on the central nervous system. The regulation of body temperature is an ideal benchmark to study the toxicity of the anti-ChE insecticides in experimental mammals and humans. The inhibition in acetylcholinesterase (AChE) activity, and subsequent stimulation of cholinergic pathways in the central and peripheral nervous systems is a key mechanism responsible for driving changes in body temperature and activation of thermoregulatory effectors. Body size and ambient temperature are perhaps the most critical factors governing the thermoregulatory effects of these toxicants. Small mammals undergo a marked increase in heat loss and become hypothermic when exposed to anti-ChEs. Small mammals exposed to these agents lower their body temperature by selective activation of heat loss thermoeffectors. This hypothermic response is often protective and increases the likelihood of surviving the toxic insult. Large mammals such as humans are unable to take advantage of this hypothermic response, and it is not clear whether a fever from these toxicants will affect the health effects of these agents. It appears that exercise and/or heat stress will exacerbate the toxic effects of anti-ChE insecticides and nerve gas agents. The redistribution of blood to the skin combined with sweating will increase the cutaneous absorption of OP agents that are applied to the skin. The increase in pulmonary ventilation during exercise combined with higher tissue temperature is bound to increase the intake and toxicity of airborne anti-ChE agents.