Caloric intake and hypothalamic neurotransmitters in Zucker rats made acutely diabetic with streptozocin.
Zucker rats, lean and obese, treated with low dose intraperitoneal injections of streptozocin become hyperglycemic within 24h. Insulin levels fall, although the obese animal remains hyperinsulinemic. Associated with these changes in glucose and insulin there are transient decreases in caloric intake. Macronutrient selection studies show that protein consumption decreases. There is a trend for fat intake to decrease. The levels of hypothalamic neurotransmitters in the lean animals are not altered by streptozocin. The levels of 5-hydroxyindoleacetic acid increases in the streptozocin-treated obese animal in the paraventricular region, ventromedial region and the raphe. Serotonin is also significantly increased in the paraventricular region of the obese rat. These results suggest that acutely, treatment with streptozocin injures pancreatic islets, causing, in turn, decreases in insulin levels so that hyperglycemia ensues in both phenotypes. Associated with these perturbations are decreases in caloric intake. The magnitude of change in insulin levels is much greater in the obese rat. It is hypothesized that in the obese Zucker rat decrements in food intake are mediated by increase in serotonin turnover in the hypothalamus and these changes are related to changes of insulin levels. These data support the concept that circulating insulin affects hypothalamic neurotransmitters.
Svec
Frank
F
Obesity Research Program, Departments of Medicine, Physiology, and Biology, Louisiana State University Health Sciences Center, New Orleans, LA, USA. fsvec@lsuhsc.edu
Robinson
Patrick
P
Michel
Leslie
L
Bradley
Jessica
J
Corll
Connie
C
Porter
Johnny R
JR
D000818:Animals; D001786:Blood Glucose / Q000032:analysis; D003921:Diabetes Mellitus, Experimental / Q000378:metabolism*; D004032:Diet; D002149:Energy Intake; D005951:Glucose Tolerance Test; D006897:Hydroxyindoleacetic Acid / Q000032:analysis; D007031:Hypothalamus / Q000737:chemistry*; D007328:Insulin / Q000097:blood; D018377:Neurotransmitter Agents / Q000032:analysis*; D009765:Obesity / Q000378:metabolism; D010286:Paraventricular Hypothalamic Nucleus / Q000737:chemistry; D011903:Raphe Nuclei / Q000737:chemistry; D051381:Rats; D011924:Rats, Zucker; D012701:Serotonin / Q000032:analysis; D014697:Ventromedial Hypothalamic Nucleus / Q000737:chemistry
D001786:Blood Glucose; D007328:Insulin; D018377:Neurotransmitter Agents; D012701:Serotonin; D006897:Hydroxyindoleacetic Acid