ROLE OF ADRENOCEPTORS INVITRO AND INVIVO IN THE EFFECTS OF LITHIUM ON BLOOD-GLUCOSE LEVELS AND INSULIN-SECRETION IN THE RAT

Pretreatment of rats with the non-selective α-adrenoceptor antagonist dihydroergotamine counteracts the inhibition of glucose-induced insulin secretion caused by lithium both in vitro and in vivo. The present study was therefore carried out to specify further which type of adrenoceptor is involved in lithium-induced hyperglycaemia and inhibition of insulin secretion. The lithium-induced effects were reversibly blocked by pretreatment of rats with the α2-adrenoceptor antagonist yohimbine or a combination of yohimbine and the non-selective β-receptor antagonist propranolol, whereas the α1-receptor antagonist prazosin and propranolol alone were ineffective in blocking these effects. These findings suggest that the effects of lithium on plasma glucose and insulin levels are mediated mainly by the stimulation of α2-adrenoceptors.