Arecoline has biomedical importance, but it has untoward side effects on 
endocrine functions. The aim is to investigate its role on adrenal activity 
under thermal stress by ultrastructural and hormonal parameters in mice. Cold 
(4 °C) or heat (37 °C) stress, or arecoline (10 mg/kg body wt), each for 7 days 
in cold or heat stress stimulated adrenocortical activity ultrastructurally with 
an elevation of corticosterone level. Adrenomedullary activity was suppressed in 
cold stress with depletion of catecholamine levels. In heat stress, 
adrenomedullary activity was stimulated ultrastructurally with an elevation of 
catecholamine levels. Arecoline treatment alone, or in cold or heat stress 
suppressed adrenomedullary activity, judged by ultrastructural and hormonal 
parameters. Arecoline treatment caused hypoglycemia with an elevation of 
glycogen level, but cold or heat stress, or arecoline treatment in thermal 
stress caused hyperglycemia, with a fall in glycogen profile. Thus, arecoline in 
thermal stress plays a dual role on adrenal function and glucose-glycogen 
homeostasis in mice.