抄録
Galanin-like peptide (GALP) is a 60 amino-acid peptide, and the GALP mRNA is restricted to neurons in the hypothalamic arcuate nucleus (Arc) and pituicytes in the posterior pituitary gland (PP). Chronic osmotic stimulus caused by dehydration and salt loading induced the GALP gene expression in the PP of rats, but it remains unknown whether acute osmotic stimulus such as intraperitoneal (i.p.) injection of hypertonic saline induces the GALP gene expression, and the time-course pattern of the GALP gene expression after acute osmotic stimulus. We examined the dose-response (2% BW, 2.8, 4.5, 6.0 and 9.0% NaCl) and time-course (6.0% NaCl, 1, 3, 6, 12 and 24 h) effects of acute osmotic stimulus on GALP mRNA levels in the Arc and PP of rats, using in situ hybridization histochemistry. After i.p. injection of hypertonic saline (6.0%), plasma osmolality increased significantly at 1 h, and plasma sodium concentration also increased significantly at 1 and 3 h. The GALP mRNA level in the PP increased significantly 6 h after i.p. injection of hypertonic saline (6.0 and 9.0%), but that in the Arc did not change. The GALP mRNA level in the PP also increased significantly 3 and 6 h after i.p. injection of hypertonic saline (6.0%). These results showed that the GALP gene expression in the PP was inducted 3 h after acute osmotic stimulus, and the gene expression might be regulated by plasma osmolality and/or plasma sodium concentration. [J Physiol Sci. 2007;57 Suppl:S172]
