Effects of small doses of colchicine on the components of the hypothalamo-neurohypophysial system of the rat

Summary Small doses (3.5 g and 7 g) of colchicine injected intracisternally caused an interruption of transport of secretory material from the supraoptic and paraventricular nuclei of the hypothalamus to the neural lobe of the pituitary gland. Transport was assessed by direct measurement of the incorporation of ³⁵S] cysteine into neurophysins, by radioimmunoassay of accumulated material in discrete areas of the system and by immunocytochemistry. The larger dose (7 g) switched off transport completely during the first 24 h but the system began to recover within three to four days. Colchicine had little, if any, effect on synthesis; comparison of the relationships of the apparent amounts of immunoreactive neurophysins and immunoreactive hormones in the arrested product led to the conclusion that processing of the hormone precursors continues within the secretory granules which accumulated in the perikarya.Supported by the Medical Research Council and the Science Research Council. E.M.R. was in receipt of an exchange fellowship under the auspices of CONICYT of Chile and The Royal Society. The authors are grateful for the careful technical assistance of Mr. Peter Rees