The Effects of leptin on thermosensitive neurons in the anterior hypothalamus of the rat

Abstract

The hormone leptin is thought to play a role in regulating body fat and metabolism in mammals through its ability to alter the activity of anterior hypothalamus (AH) neurons that play a role in homeostatic control. Recent studies have shown that when leptin is injected either intravenously or into the ventricles in rodents, an increase in body temperature is detected, which may be a possible through which leptin inhibits feeding behavior. On the basis of current models for thermoregulation, we hypothesized that warm sensitive neurons in the AH would exhibit a decrease in firing rate in response to leptin while temperature insensitive neurons would respond with an increase in firing rate. Using a tissue slice preparation, the extracellular activity of AH neurons was recorded to classify their responses to temperature and to leptin (100 μM). The majority of warm sensitive neurons decreased their firing rates. While nearly 50% of the temperature insensitive neurons responded with an increase in firing rate, the majority of the remaining temperature insensitive neurons showed decreases in firing rate. This contrast in responses may relate to the specific efferent connections of these thermoregulatory neurons which will be characterized in a future study. This research was supported by grants from the NIH (NS053794, NS065461 & NS053794-01S1) and a Howard Hughes Medical Institute grant to the College of William and Mary.