Action of colchicine on axonal flow and pituicytes in the hypothalamopituitary system of the rat.

Changes in the hypothalamo-pituitary tract and the pituicytes of the rat were studied after intrathecal and intraperitoneal injections of colchicine. Radioautography with 35S-cysteine demonstrates that intrathecal colchicine prevents the migration of neurosecretory granules from the supraoptic and paraventricular nuclei to the posterior lobe of the pituitary. This results in accumulations of neurosecretory granules and in the formation in the axons of elongated structures resembling neurosecretory products, although they sometimes have a fibrillary content. Neurotubules appear to remain intact in these conditions. The stimulation of the posterior pituitary by dehydration, in particular after injection of the diuretic furosemide, leads to an increased activity of pituicytes. When colchicine is injected at the same time as furosemide, a considerable new formation of centrioles is observed in the pituicytes. These become associated with ciliary vesicles, and form numerous cilia of the 9 + 0 type. An increased number of centrioles is also seen in the endothelial cells of the posterior lobe of the pituitary. These apparently paradoxical results were briefly discussed in relation to the action of colchicine on neurotubules and axonal flow and to the limited data from the literature indicating a stimulation of cilia formation under the action of colchicine and other drugs.