Increased brain 3H-paraminoclonidine (alpha 2-adrenoceptor) binding associated with perpetuation of diet-induced obesity in rats.
Brain alpha-adrenoceptor (alpha-AR) binding was examined as a possible explanation for the persistence of diet-induced obesity (DIO) or resistance (DR) in rats after they were returned to chow from a high-energy, fat and sucrose diet (CM diet). Adult Sprague-Dawley rats (n = 28) were fed the CM diet for 12 weeks. Those that gained more weight than chow-fed controls were classified as DIO and those that gained the same weight as controls were called DR. The 10 heaviest DIO and 8 lightest DR rats were then placed on chow for an additional 14 weeks. After the entire 26-week period, the body weights of DIO rats were still 21 per cent greater and those of the DR rats were 9 per cent less than 7 chow-fed controls. DIO retroperitoneal fat pads were also 62 per cent heavier while DR pads were equal to controls. Plasma insulin and glucose levels were comparable in all 3 groups. Receptor autoradiographic studies of brain alpha 1-AR (3H prazosin; PRZ) and alpha 2-AR (3H-paraminoclonidine; PAC) adrenoceptor binding were carried out using these animals at the end of 26 weeks. Binding to alpha 1-AR was comparable in all groups but alpha 2-AR binding was 47-103 per cent higher in DIO compared to DR and chow-fed controls in 14 of 17 brain areas assessed. These included the dorsomedial, ventromedial and paraventricular hypothalamic n. and all amygdalar areas. Such widespread differences in alpha 2-AR binding in rats fed the same diet but of differing body weights suggest that alpha 2-AR binding is a marker for differences in body weight regulation and may be important in the control of the differences in weight gain.
Levin
B E
BE
Neurology Service, Department of Veterans Affairs Medical Center, East Orange, NJ 07019.
D000316:Adrenergic alpha-Agonists / Q000378:metabolism; D000818:Animals; D001921:Brain / Q000378:metabolism*; D003000:Clonidine / Q000031:analogs & derivatives* / Q000378:metabolism; D004032:Diet / Q000009:adverse effects; D008297:Male; D008954:Models, Biological; D009765:Obesity / Q000209:etiology / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains; D011942:Receptors, Adrenergic, alpha / Q000378:metabolism*
D000316:Adrenergic alpha-Agonists; D011942:Receptors, Adrenergic, alpha; C016986:apraclonidine; D003000:Clonidine