Central regulation of feeding behavior during social isolation of rat: evidence for the role of endogenous CART system.
OBJECTIVE
Although hyperphagia and body weight gain are well-recognized consequences of social isolation, the underlying mechanisms are not understood. The aim of this work is to test the possibility that the endogenous cocaine- and amphetamine-regulated transcript peptide (CART) may be involved in the process.


METHODS
Socially isolated rats were screened for increase in food intake and body weight, and the modifications of these parameters by CART were evaluated. Furthermore, isolated animals were re-socialized and screened for reversal of these effects. Response of the endogenous CART system, in certain hypothalamic nuclei of the isolated and re-socialized rats, was evaluated with immunohistochemistry.


METHODS
Fifty days old naive male Sprague-Dawley rats were used.


METHODS
The effects of CART/CART antibody on the social isolation and subsequent re-socialization on feeding and body weight changes were monitored. Moreover, the immunohistochemical response of endogenous CART system to social isolation and re-socialization was analyzed morphometrically.


RESULTS
While social isolation of rats for a period of 6 weeks caused progressive increase in food consumption and body weight gain, these rats showed a significant reduction in food intake and body weight when injected daily with CART via intracerebroventricular (i.c.v.) route, for the following 7 days. The re-socialization of isolated rats reduced food intake and body weight to the control levels. These effects of re-socialization were attenuated by immunoneutralization of the endogenous CART by i.c.v. CART antibody. Social isolation also resulted in a drastic reduction in CART immunoreactivity in the cells and/or fibers in the hypothalamic areas like dorsomedial, ventromedial, lateral, paraventricular and arcuate nuclei, recognized for their role in feeding. On the other hand, the CART immunoreactivity profile was fully restored following 7 days of re-socialization of the isolation-reared rats.


CONCLUSIONS
Social isolation might down-regulate the hypothalamic CART-containing system, which in turn may lead to increase in food intake and body weight.
Department of Pharmaceutical Sciences, Rashtrasant Tukadoji Maharaj Nagpur University Campus, Nagpur, Maharashtra, India.
K T
KT
Nakhate
D M
DM
Kokare
P S
PS
Singru
N K
NK
Subhedar
D000818:Animals; D001835:Body Weight / Q000187:drug effects / Q000502:physiology*; D004195:Disease Models, Animal; D004435:Eating / Q000187:drug effects / Q000502:physiology*; D005247:Feeding Behavior / Q000187:drug effects / Q000502:physiology*; D007276:Injections, Intraventricular; D008297:Male; D009419:Nerve Tissue Proteins / Q000494:pharmacology / Q000502:physiology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012934:Social Isolation; D012951:Socialization; D000098882:Cocaine- and Amphetamine-Regulated Transcript Protein
D009419:Nerve Tissue Proteins; D000098882:Cocaine- and Amphetamine-Regulated Transcript Protein