Section Review: Oncologic, Endocrine and Metabolic Adrenoceptors and imidazoline binding sites in the endocrine pancreas as targets for anti-hyperglycaemic drugs

The rate of insulin secretion from the endocrine pancreas is controlled principally by metabolic stimuli, although other agents, including hormones and neurotransmitters, are important modulators of insulin secretion. Among these, the catecholamines are particularly effective inhibitors of insulin secretion; a response that is mediated by activation of alpha-2-adrenoceptors present on islet B-cells. In view of the potent inhibitory effects of catecholamines on insulin secretion, the proposition has been advanced that increased sympathetic nervous activity (or enhanced islet responsiveness to catecholamines) might contribute to the impairment of insulin secretion observed in certain patients with non-insulin-dependent diabetes mellitus. If true, then it follows that circulating insulin levels should be increased upon administration of alpha-2-adrenoceptor antagonists to such patients. Evidence has accumulated which supports this concept, although this evidence is equivocal since the insulin secretagogue ac...