Acute versus Subchronic Pyridostigmine Administration: Effects on the Anticholinergic Properties of Atropine

Acute, subchronic and chronic exposures to cholinergic compounds may result in differing effects. The efficacy of pyridostigmine bromide PY prophylaxis against organophosphorus poisoning depends on post exposure atropine AT administration. AT induces a dose-dependent increase in rate of rise of core temperature in heat exposed humans and rats. To determine whether ATs anticholinergic potency is altered following PY administration, we examined ATs effects following acute or subchronic 2 weeks PY administration in the sedentary heat-stressed rat. Unrestrained rats were used in the following 8 groups of 12 acute a,2 injections via tail vein aSALSAL, aSALAT, aPYSAL, aPYAT subchronic c, osmotic pump tail vein cSALSAL, cSALAT, cPYSAL, CPYAT SAL- saline, AT- 200 ugkg, aPY- 100 ugkg, cPY- 20 ughr. Fifteen minutes following the final injection, rats were subjected to an ambient temperature of 41.5 deg C until a core temperature of 42.6 deg C was attained.