[The central nervous system-endocrine pancreas axis].

Some results suggesting the existence of gluco- and/or insulin-sensitive sites within the central nervous system (CNS) are recalled. In summary, it seems that when these sites are activated by the presence of glucose or insulin, there is an activation of the parasympathetic nervous system which is responsible for an increased peripheral insulin secretion and/or an hypoglycemia. This could possibly favour glucose disposal. Inversely, when the CNS lacks energy substrates, a cascade of events occurs which tend to increase peripheral glycemia. Bilateral lesions of the ventromedial hypothalamus (VMH) bring about a very early occurring hypersecretion of insulin which can be rapidly and completely abolished by vagotomy. It has also been shown that genetically pre-obese rats (fa/fa) do hypersecrete insulin in response to an i.v. glucose load. This suggests that hypersecretion of insulin of these animals could play a causative role in the development of their obesity. Moreover, this hypersecretion of insulin observed in genetic pre-obesity is abolished by acute atropine administration indicating the involvement of the parasympathetic nervous system in the development of their hyperinsulinemia and subsequent obesity. Cephalic phase insulin secretion seems to "optimalize" insulin secretion that occurs following a meal, as it appears to permit adequate glucose utilization and therefore glucose tolerance. Indeed, animals which are lacking cephalic phase insulin secretion do hypersecrete insulin while remaining hyperglycemic for a longer period of time when compared to animals which have a cephalic phase insulin secretion. Hypothalamic factors present in the ventromedial or the ventrolateral hypothalamus have been shown to have insulin secretion promoting activity when administered in vivo or in vitro to donor rats. It remains to be shown whether such factors are indeed released into the blood (humoral factors) or whether they are neuromodulators and/or neurotransmitters.