Stimulus-related changes in the dendrites of magnocellular neurones.

A Golgi-Cox study was undertaken to determine whether enhanced electrical activity was associated with any morphological changes in the dendrites of the magnocellular neurones in the hypothalamic supraoptic nucleus. Brattleboro rats, animals dehydrated by administration of 2% sodium chloride solution instead of drinking water and animals given 1% sodium chloride solution and deoxycortone to induce vasopressin-dependent hypertension were compared with controls. In each of the stimulated groups, the cell bodies were hypertrophied implying that the stimuli were effective. Dendritic span (the area of a triangle drawn round, and containing the entire Golgi-stained dendritic tree) was significantly increased (p less than 0.01) in Brattleboro rats but was decreased by sodium chloride-induced dehydration (p less than 0.01). Deoxycortone treatment reversed the reduction induced by dehydration. Hippocampal cells showed no significant differences. Thus, the cells of the magnocellular system rapidly alter their morphology when stimulated but the changes are more complex than a simple hypertrophy associated with enhanced activity.