Effects of intragastric water infusion and gastric distension on hypothalamic neuronal activity.

The effects of gastric water infusion and distension were examined in neurons from various parts of the rat brain. Neurons in the lateral preoptic-lateral hypothalamic-medial forebrain bundle (LPA-LH-MFB) neuropil were sensitive to gastric water infusion and distension. Cells randomly selected and examined in other brain areas were less sensitive to the same stimulation which indicated that the effects were relatively specific. The results, in terms of changes in neuronal discharge frequency from an established baseline, indicate that many cells in the lateral preoptic-lateral hypothalamic-medical forebrain bundle area are affected by intragastric water infusion and gastric distension within a time period during which changes in drinking would normally occur. These neurons were also affected differentially by acute water deprivation. LPA-LH-MFB neurons in 24 hr water deprived animals were significantly more sensitive to water infusions and less sensitive to stomach distension when compared to cells recorded in animals maintained on ad lib eating and drinking. Some of these same neurons were also sensitive to changes in the extracellular concentrations of sodium and glucose. The results are discussed in terms of the involvement of the lateral preoptic-lateral hypothalamic-medial forebrain bundle neuropil in ingestive behavior.