Thyroid hormone-dependent regulation of galanin synthesis in neurons and glial cells after colchicine administration.

Galanin and galanin message-associated peptide (GMAP) synthesis is up-regulated in neurons and glial cells in the adult rat brain by different experimental manipulations, including intracerebroventricular colchicine. We have previously reported that the galanin expression is severely attenuated in some neurons in adult hypothyroidism. In order to further investigate the role of thyroid hormone for the in vivo regulation of galanin gene expression, we have studied the effect of intraventricular administration of colchicine on prepro-galanin (ppGAL) mRNA expression in the brain of normal and hypothyroid, adult male rats. While ppGAL mRNA levels were markedly elevated in a great number of glial cells in the white and gray matter in normal rats, this effect was almost completely abolished in hypothyroid rats. In contrast, colchicine-induced up-regulation of galanin/GMAP expression occurs in the hypothalamic paraventricular nucleus both of euthyroid and hypothyroid rats, although with a slightly different time course.