Chemical sympathectomy alters food intake and thermogenic responses to catecholamines in rats.
It has been suggested that the sympathetic nervous system contributes to the short-term control of feeding. The adrenergic innervation of some splanchnic organs seems to be especially involved in such processes, since catecholamines reduce feeding only when injected intraperitoneally or intraportally. In this work, the effects of neonatal sympathetic denervation with guanethidine (Gnt) upon food intake were assessed in adult rats. Gnt-treated male rats had lower body weight gain. The hypophagic response to intraperitoneal (ip) norepinephrine was 70% higher in Gnt-treated animals as compared to controls (P < 0.05); that of epinephrine (E) by 33% (P < 0.05) and that of isoproterenol was not significantly modified. As in normal rats, the hypophagic effect was much stronger after ip than after intramuscular (im) administration (P < 0.05). On the other hand, resting oxygen consumption (VO2) was consistently lower in denervated animals. Ip E administration did not modify VO2, while im E caused increased motor activity and VO2 (P < 0.05). In contrast to control rats, the respiratory exchange ratio in ad libitum fed Gnt rats did not decrease after Ip E administration, suggesting a lack of effect upon lipid mobilization. The lower rate of body weight gain induced by neonatal Gnt sympathectomy might be due to lower daily food intake possibly related, in part, to the sensitization of the alpha-adrenergic porto-hepatic response to endogenous catecholamines. Compared with controls, Gnt-treated rats also showed a limited thermogenic capacity not related to feeding, and a greater degree of carbohydrate oxidation, possibly due to a defect in E-induced lipolysis, which is beta-adrenergic.
Villanueva
Iván
I
Departamento de Fisiología, Escuela Nacional de Ciencias Biológicas, I.P.N. México, 11340 Col. Casco de Sto. Tomás, Mexico. ivillanu@redipn.ipn.mx
Piñón
Manuel
M
Quevedo-Corona
Lucía
L
Martínez-Olivares
Rubén
R
Racotta
Radu
R
D000322:Adrenergic Agonists / Q000494:pharmacology; D000319:Adrenergic beta-Antagonists / Q000494:pharmacology; D000818:Animals; D001831:Body Temperature / Q000187:drug effects / Q000502:physiology*; D001835:Body Weight / Q000187:drug effects; D002153:Calorimetry, Indirect; D002395:Catecholamines / Q000378:metabolism / Q000494:pharmacology*; D004435:Eating / Q000187:drug effects / Q000502:physiology*; D004734:Energy Metabolism / Q000187:drug effects; D005260:Female; D006145:Guanethidine; D008297:Male; D009043:Motor Activity / Q000187:drug effects; D010101:Oxygen Consumption / Q000187:drug effects; D011659:Pulmonary Gas Exchange / Q000187:drug effects; D051381:Rats; D017208:Rats, Wistar; D013563:Sympathectomy, Chemical; D013565:Sympatholytics; D014018:Tissue Distribution
D000322:Adrenergic Agonists; D000319:Adrenergic beta-Antagonists; D002395:Catecholamines; D013565:Sympatholytics; D006145:Guanethidine