Stress and Colchicine do not Induce the Release of Galanin from the External Zone of the Median Eminence

The aim of the present study was to verify the hypothesis that stress exposure modifies the content and release of galanin in the hypothalamic paraventricular nucleus and the median eminence. Colchicine and immobilization served as stress stimuli, and the changes in galanin immunoreactivity were compared with those in corticotropin-releasing hormone and vasopressin. In control animals, a limited number of galanin perikarya were identified in the paraventricular nucleus. The high dose (75 g) of colchicine enhanced galanin in both parvicellular and magnocellular subdivisions, as analysed 72 h later. In the median eminence, galanin accumulated only in the external zone. High- dose colchicine did not affect galanin, while corticotropin- releasing hormone and vasopressin were depleted from the median eminence. Immobilization (120 min) neither alone nor in combination with colchicine influenced galanin immuno-reactivity in the external zone. The low dose of colchicine induced an unexpected accumulation of galanin in the internal zone of the median eminence, which was further increased by subsequent immobilization. In the external zone, low-dose colchicine induced a complete disappearance of vasopressin, substantial depletion of corticotropin-releasing hormone and no changes in galanin immunoreactivity. The present studies demonstrate that galanin in the external zone of the median eminence is not influenced by colchicine or by immobilization stress.