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Acta Physiologica Congress

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Acta Physiologica 2011; Volume 202, Supplement 684
The Joint Conference (FAMÉ 2011) of the LXXVth Meeting of the Hungarian Physiological Society, XVIth Meeting of the Hungarian Society of Anatomists, Experimental Section of the Hungarian Society for Experimental and Clinical Pharmacology and Hungarian Society for Microcirculation and Vascular Biology
6/8/2011-6/11/2011
Pécs, Hungary


BODY COMPOSITION INFLUENCES ACUTE THERMOREGULATORY EFFECTS OF CENTRAL ALPHA-MSH INJECTION
Abstract number: P74

Sipos1 V., Rostas1 I., Soos1 S., Balasko1 M., Petervari1 E., Szekely1 M.

Aims: 

Alpha-melanocyte-stimulating hormone (alpha-MSH), an endogenous agonist of the hypothalamic melanocortin (MC) system has coordinated catabolic actions in the regulation of energy balance: via suppression of food intake and an increase in metabolic rate, body weight is reduced. Our previous results suggested a role for alpha-MSH in thermoregulation. Other observations showed that body composition had a significant influence on the classical catabolic actions of alpha-MSH. Therefore, the aim of the present study was to analyze the effects of body composition on the thermoregulatory effects of alpha-MSH.

Methods: 

Thermoregulatory effects of an acute intracerebroventricular (ICV) alpha-MSH injection (0 or 5 mg) were analyzed in 6 month-old male Wistar rats with different body compositions: in ad libitum (normally) fed (NF6), calorie-restricted (CR6, 16 g/day standard laboratory chow) and high-fat diet-induced obese (HF6, IPS TestDiet, 60% fat-calories) groups at slightly subthermoneutral ambient temperature (25–26°C). Oxygen consumption, core (Tc) and tail skin temperatures (Ts, indicating heat loss) of partially restrained rats were recorded by indirect calorimetry (Oxymax) and by thermocouples.

Results: 

Upon acute ICV injection of alpha-MSH, Tc became elevated in NF6 and CR6 rats, while this rise was not significant in HF6 animals. Oxygen consumption increased in all animal groups. Tail skin temperature has risen immediately upon alpha-MSH injection in NF6 and HF6 rats, while this rise was delayed in CR6 animals by about 20 minutes.

Conclusions: 

Body composition has a complex influence on central thermoregulatory effects of alpha-MSH. Although the increase in metabolic rate was significant in all groups, varying degrees of heat loss activation resulted in different hyperthermic responses. Alpha-MSH-induced hyperthermia proved to be most pronounced in CR rats, whereas HF animals failed to show a significant rise in Tc. This pattern resembles the hypermetabolism observed during a central alpha-MSH infusion in a biotelemetric system.

Support: 

OTKA PD84241, PTE AOK-KA-34039-02/2010

To cite this abstract, please use the following information:
Acta Physiologica 2011; Volume 202, Supplement 684 :P74

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