24 hour fasting and adrenoreceptor blocking agent influence on adrenal catecholamine synthesis rate changes induced by combined thermal and immobilization stress in rats.

The catecholamine (CA) depletion degree in rat adrenal medulla, the survival time (ST) and rectal temperature changes induced by combined thermal and immobilization stress were examined with the aim to prove tha alpha- and beta-adrenoreceptor sensitivity decrease implication in 24 hour fasting-induced changes of the above mentioned phenomena. The significant ST increase in strong stressful situations and the adrenal CA turnover augmentation in fed and fasted-propranolol or dihydroergotamine pretreated rats compared to untreated ones provided evidence that alpha- and beta adrenoceptor blockade causes adrenal CA turnover increase and ST prolongation similar to effects observed in our previous experiments. Thus the implication of fasting induced adrenoreceptor downregulation in adrenal CA turnover augmentation and ST prolongation of fasted rats in strong stressful conditions was suggested and the possible mechanisms of these phenomena have been discussed.