Several lines of evidence have implicated the hypothalamic ventromedial nucleus (VMH) in the control of caloric homeostasis. For example, the activity of VMH neurons depends on energy availability. We tested the hypothesis that energy balance may involve the remodeling of the dendritic arbor of VMH neurons. We compared two groups of animals: one group had ad libitum access to food, and the other experienced 10-d restricted access to food. As expected, the food-deprived group lost body weight and had reduced levels of glucose, insulin, and leptin. VMH neurons were visualized after Golgi impregnation, and dendrite length was measured. Food deprivation had differential effects on VMH neurons. In particular, within the ventrolateral VMH, for neurons with long primary dendrites (LPDs) that extended in the lateral, but not medial, direction, the LPDs were 31% shorter. These same neurons exhibited a 32% reduction in the number of other dendrites without a change in soma size. In contrast, within the dorsomedial VMH, for neurons with medially, but not laterally, extended LPDs, the soma area was reduced by 28%. However, neurons in the dorsomedial VMH did not display a change in the length or number of dendrites, regardless of LPD direction. Thus, although structural changes during calorie depletion occur in both the dorsomedial and ventrolateral VMH, only the latter exhibits a remodeled dendritic arbor. These results also suggest that the direction of the LPD may be an important marker of neuronal function in the VMH.
Estradiol and progesterone differentially regulate the dendritic arbor of neurons in the hypothalamic ventromedial nucleus of the female rat (Rattus norvegicus)