title: Chronic intracerebroventricular infusion of insulin failed to alter brain insulin-binding sites, food intake, and body weight.
abstract: The present study was performed to explore the role of exogenous insulin in CSF in the control of energy balance in the rat. For this purpose, adult male Sprague-Dawley rats carrying an indwelling cannula in the right lateral cerebral ventricle were infused for a maximum of 10 days with insulin (Actrapid) at various rates (starting at 0, 45, 85, 170, and 600 ng/day) or anti-insulin antibody (IgG fraction; diluted 1:10 wt/vol) with an osmotic minipump. All those treatments did not modify the growing rates; neither total daily food intake nor the circadian rhythm of food intake was further modified. The chronic insulin infusion starting at 600 ng/day resulted in a chronic significant increase in CSF insulin levels without changing the plasma insulin level. It failed to alter specific insulin binding sites to Triton X-100 solubilized microsomal membranes from various brain areas (cerebral cortex, olfactory bulbs, and lateral and medial hypothalami) at the end of the 5- or 10-day period of insulin infusion. Purification of insulin receptors on a wheat germ agglutinin did not reveal any further effect of insulin. From these results, it seems unlikely that the input to the brain insulin-effector systems could arise from CSF insulin.
mesh_terms: D000818:Animals; D001835:Body Weight / Q000187:drug effects*; D001921:Brain / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism; D002540:Cerebral Cortex / Q000378:metabolism; D002552:Cerebral Ventricles / Q000187:drug effects; D002940:Circadian Rhythm; D004435:Eating / Q000187:drug effects*; D007031:Hypothalamus / Q000378:metabolism; D007116:Immunization, Passive; D007328:Insulin / Q000008:administration & dosage / Q000097:blood / Q000134:cerebrospinal fluid / Q000276:immunology / Q000494:pharmacology*; D061389:Insulin, Regular, Pork; D008297:Male; D009830:Olfactory Bulb / Q000378:metabolism; D051381:Rats; D011919:Rats, Inbred Strains; D011972:Receptor, Insulin / Q000378:metabolism*
chemical_list: D007328:Insulin; D061389:Insulin, Regular, Pork; C000006:insulin, neutral; D011972:Receptor, Insulin