Hashimoto Hirofumi, Fujihara Hiroaki, Kawasaki Makoto, Saito Takeshi, Shibata Minori, Otsubo Hiroki, Takei Yoshio, Ueta Yoichi
Department of Physiology, School of Medicine, University of Occupational and Environmental Health, 1-1 Iseigaoka, Yahatanishi-ku, Kitakyushu 807-8555, Japan.
Endocrinology. 2007 Apr;148(4):1638-47. doi: 10.1210/en.2006-0993. Epub 2007 Jan 25.
Ghrelin is known as a potent orexigenic hormone through its action on the brain. In this study, we examined the effects of intracerebroventricular (icv) and iv injection of ghrelin on water intake, food intake, and urine volume in rats deprived of water for 24 h. Water intake that occurred after water deprivation was significantly inhibited by icv injection of ghrelin (0.1, 1, and 10 nmol/rat) in a dose-related manner, although food intake was stimulated by the hormone. The antidipsogenic effect was as potent as the orexigenic effect. Similarly, water intake was inhibited, whereas food intake was stimulated dose dependently after iv injection of ghrelin (0.1, 1, and 10 nmol/kg). The inhibition of drinking was comparable with, or even more potent than, atrial natriuretic peptide (ANP), an established antidipsogenic hormone, when administered icv, although the antidipsogenic effect lasted longer. ANP had no effect on food intake. Urine volume decreased dose relatedly after icv injection of ghrelin but not by ANP. Intravenous injection of ghrelin had no effect on urine volume. Because drinking usually occurs with feeding, food was withdrawn to remove the prandial drinking. Then the antidipsogenic effect of ghrelin became more potent than that of ANP and continued longer than when food was available. Expression of Fos was increased in the area postrema and the nucleus of the tractus solitarius by using immunohistochemistry after icv and iv injection of ghrelin. The present study convincingly showed that ghrelin is a potent antidisogenic peptide in rats.
胃饥饿素因其对大脑的作用而被认为是一种强效的促食欲激素。在本研究中，我们检测了脑室内（icv）和静脉注射胃饥饿素对缺水24小时大鼠的水摄入量、食物摄入量和尿量的影响。icv注射胃饥饿素（0.1、1和10 nmol/只大鼠）以剂量相关的方式显著抑制了缺水后发生的水摄入，尽管该激素刺激了食物摄入。抗利尿作用与促食欲作用一样强大。同样，静脉注射胃饥饿素（0.1、1和10 nmol/kg）后，水摄入受到抑制，而食物摄入呈剂量依赖性增加。当icv给药时，与已确定的抗利尿激素心房利钠肽（ANP）相比饮水抑制作用相当，甚至更强，尽管抗利尿作用持续时间更长。ANP对食物摄入没有影响。icv注射胃饥饿素后尿量呈剂量相关减少，但ANP没有此作用。静脉注射胃饥饿素对尿量没有影响。由于饮水通常与进食同时发生，因此去除食物以消除餐时饮水。然后，胃饥饿素的抗利尿作用比ANP更强，且持续时间比有食物时更长。icv和静脉注射胃饥饿素后，通过免疫组化法检测发现，最后区和孤束核中Fos表达增加。本研究令人信服地表明，胃饥饿素在大鼠中是一种强效的抗利尿肽。
