Insulin-sensitive glucoreceptors in rat preoptic area that regulate FFA mobilization.

Previous studies indicated that a longitudinal pathway connecting preoptic, lateral, and posterior hypothalamic areas participates in the process of free fatty acid (FFA) mobilization in the rat. In the present experiments, the presence of sensitive neurons in the preoptic area was investigated by examining the effects of topical stimulation with 2-deoxyglucose (2-DG) or insulin on the levels of plasma FFA in conscious unrestrained rats. Microinjections of minute amounts (50 micrograms and 1 microliter) of 2-DG into the preoptic area of fed animals induced rapid increases in the concentration of plasma FFA. Microinjections of insulin (5 microU and 0.5 microliter) produced sharp decreases of the elevated plasma FFA levels in fasted rats. Both 2-DG and insulin induced small increases in plasma glucose that did not differ from similar increases induced by equal volumes of 0.15 M NaCl. The results provide direct evidence for the presence within the preoptic area of insulin-sensitive glucoreceptors involved in FFA mobilization. The data suggest that activation of these receptors and increased sympathetic outflow to adipose tissue contributes to fasting lipolysis.