Influence of the subfornical organ on meal-associated drinking in rats

A lesion of the subfornical organ (SFO) may disrupt drinking after a meal o f dry chow as it does drinking after intragastric administration of hyperto nic saline. Food and water intakes of SFO-lesioned (SFOX) and sham-lesioned rats were measured during 90-min tests following various lengths of food d eprivation. During the tests, all rats began eating before they began drink ing. After 20-24 h of food deprivation, latency to begin drinking after eat ing had started was longer for SFOX than for sham-lesioned rats. Plasma osm olality was elevated by 2-3% in both lesion groups at 12 min, the latency f or sham-lesioned rats to drink, but SFOX rats nevertheless continued eating and delayed drinking. Eating after shorter 4-h food deprivations and ad li bitum feeding produced more variable drinking latencies and less consistent effects of SFO lesion. During 24 h of water deprivation, SFO lesion had no effect on the suppression of food intake and did not affect food or water intakes during the first 2 h of subsequent rehydration. These findings indi cate that the SFO is involved in initiating water intake during eating and in determining drinking patterns and the amount of water ingested during a meal.