Study on the function s of growth hormone secretagogue receptor

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To clarify the role of growth hormone secretagogue receptor(GHSR), we created transgenic(Tg) rats expressing an antisense GHSR mRNA under the control of the promoter for tyrosine hydroxylase, thus selectively attenuating GHSR protein expression in the arcuate nucleus of the hypothalamus. Tg rats had lower body weight and less adipose tissue than did control rats. The stimulatory effect of GHS treatment on feeding was abolished although the amount of food intake/100 g body weight was not reduced in Tg rats. These findings suggest that GHSR is involved in the regulation of energy metabolism, Tg rats showed higher O2 consumption and CO2 production and higher body temperature. In response to high fat meal, an increase in adipose tissue was smaller in Tg rats than control rats. The level of UCP1 expression was higher in Tg rats than control rats. Ghrelin inhibited noradrenaline release in the brown adipose tissue when administered intracerebroventricularly to control rats while it induced no significant change in noradrenaline release in the brown adipose tissue of the Tg rats. These results suggest that GHSR is involved in the reduction of energy consumption through the suppression of sympathetic nervous system in the brown adipose tissue. It is also suggested that energy consumption is increased through the inhibition of ghrelin action in Tg rats, thus causing low adiposity.