Leptin Reception in the Ventromedial Nucleus of the Hypothalamus in the Aging Rats

Using immunohistochemistry, electrophysiology, and western-blot analysis we studied the expression of leptin receptors (LepR) and the effects of leptin on the firing frequency of neurons in the ventromedial nucleus (VMN) of the hypothalamus in male rats of different age groups, including 2–3, 12 or 24 months. In the hypothalamic VMN, the proportion of LepR-immunoreactive neurons varied from 58.2 ± 3.5 to 62.3 ± 3.7% and did not change with aging. The LepR content in the VMN remained stable during aging as well. However, the leptin-induced changes in firing frequency of most hypothalamic neurons switched from inhibitory in young animals to excitatory in aged rats. Thus, despite the consistent receptor composition, the neuronal response to leptin is altered in the VMN during aging.