The expression of receptors to leptin (LepR), as well as the effect of leptin on the frequency of neuronal discharges was studied in the ventromedial nucleus (VMN) of the hypothalamus in male rats of different age groups (2–3 months, 12 months and 24 months) using immunohistochemical, electrophysiological and Western blotting methods. In the hypothalamic VMN, the percentage of neurons immunoreactive to LepR ranged from 58.2 ± 3.5% to 62.3 ± 3.7% and did not change with age. The quantitative content of LepR in VMN also remained constant with age. The frequency of neuronal discharges in response to leptin administration also did not change significantly in VMN of different age groups. However, there was a change in the discharge frequency of most separate hypothalamic neurons after leptin administration, from mainly inhibitory at young ages to mainly activating in old rats. Thus, despite the constancy of the receptor composition, aging results in a qualitative change in the response of HPA neurons to leptin action.
Masliukov et al. (Wed,) studied this question.