The effect of a ventral medial hypothalamic lesion on the insulin-induced hypotensive response in normal rats.
The cardiovascular responses to insulin-induced hypoglycemia were studied in normal and ventral medial hypothalamic (VMH)-lesioned rats. The goal of this study was to investigate the role of the VMH in mediating the insulin-induced decreases in cardiovascular tone. Male Wistar rats were anesthetized with urethane/chloralose. Following the induction of anesthesia, the trachea, femoral artery, and femoral vein were cannulated. The femoral artery was attached to a pressure transducer for cardiovascular monitoring. The cardiovascular activity was recorded using a Modular Instruments Micro 5000 signal processing system. The mean arterial pressure and pulse pressures and heart rate were evaluated. In control studies, a stable plasma glucose and blood pressure were obtained with urethane/chloralose anesthesia for the duration of the experiments. Insulin (2.0 or 5.0 U/kg) significantly decreased the plasma glucose as well as the blood pressure. In VMH-lesioned rats, the lesions were accomplished by radiofrequency, and the cardiovascular response to insulin-induced hypoglycemia was investigated 1 or 6 weeks later. There was no difference in the cardiovascular response to insulin-induced hypoglycemia between the low or high insulin dose after 1 week in VMH-lesioned animals. The low dose after 6 weeks in VMH-lesioned animals did not produce a change in the mean arterial pressure response compared with controls. The pulse pressure was higher than in the sham-lesioned animals, and the plasma glucose response was greater.(ABSTRACT TRUNCATED AT 250 WORDS)
Wright-Richey
J
J
Department of Physiology, Wayne State University School of Medicine, Detroit, Michigan.
Schultz-Klarr
S
S
Dunbar
J C
JC
D000818:Animals; D001786:Blood Glucose / Q000378:metabolism; D001794:Blood Pressure / Q000187:drug effects / Q000502:physiology*; D006339:Heart Rate / Q000187:drug effects / Q000502:physiology*; D007003:Hypoglycemia / Q000139:chemically induced / Q000503:physiopathology*; D007262:Infusions, Intravenous; D007328:Insulin / Q000008:administration & dosage / Q000494:pharmacology*; D008297:Male; D011674:Pulse / Q000187:drug effects / Q000502:physiology*; D051381:Rats; D017208:Rats, Wistar; D012016:Reference Values; D013997:Time Factors; D014697:Ventromedial Hypothalamic Nucleus / Q000502:physiology*
D001786:Blood Glucose; D007328:Insulin