The short-term effects of bilateral electrical stimulation of the lateral component of the lateral hypothalamic/medial forebrain bundle area (LHA) on peripheral plasma levels of glucose (G), immunoreactive insulin (IRI) and glucagon (IRG) were measured in food-deprived, anesthetized rats in the presence of continous low i.v. glucose infusion. In normal rats LHA stimulation induced a rapid but moderate rise in IRI in the presence of a simultaneous rapid rise in G. At the end of the 5 min stimulation period the glucose-induced IRI response was clearly attenuated. In rats receiving a continous phentolamine (i.v.) infusion, the rapid IRI response was much larger in spite of only marginal rises of G. These findings suggest that electrical LHA stimulation activates two opposing mechanisms on IRI secretion, an excitatory component which is masked in the normal animal by a sympathetic α-adrenergic inhibitory component. In an attempt to define the mediating pathway of this LHA stimulation-induced IRI excitatory component, both the parasympathetic and sympathetic divisions of the autonomic nervous system were pharmacologically and surgically manipulated, all in the presence of phentolamine infusion. Neither bilateral subdiaphragmatic vagotomy, atropine, propranolol infusion, nor spinal cord transection at T1 were able to block the IRI response. These findings are consistent with a humoral mediation of this IRI stimulatory response and support the existence of a lateral hypothalamic or hypophyseal factor which is released by LHA stimulation. The implications and physiological role of the LHA in the neural control of insulin secretion and ingestive behavior are discussed.
Bibliographical noteFunding Information:
We thank Miss Dominique Rutschmann for her excellent technical assistance. ,a?~,,iws ork was supportedi n part by Grant 220.127.116.11S R from the Swiss National Science Foundation, Berne, Switz..~rlanda, nd in part by Grant 1 R01 AM25220-0\]f rom the National Institutes of Health, Bethesda,M d., U.S.A., and by a glad;> in-aidf rom Nestle,V erey, Switzerland.
- autonomic nervous system manipulation
- electrical stimulation
- lateral hypothalamic area
- plasma insulin plasma glucose