Effect of intraperitoneal and intragastric loading with water and isosmotic solutions of saline and glucose on water intake of dehydrated rats.

Female rats, dehydrated with food available for 24 hr, lost 6 to 8% of body weight. When allowed access to water, 40 to 60% of the weight deficit was replaced within the first hr. Either intraperitoneal (IP) or intragastric (IG) water loads (3% of body weight) administered just prior to return of water inhibited water intake of dehydrated rats nearly completely during the first hr of access to water. In contrast, similar loads of isotonic saline were much less effective. Even when 0.5 and 1.0 hr elapsed between IP loading (3% of body weight) with isotonic saline and access to water, water intake was not significantly different from that of untreated, dehydrated controls. In contrast, a similar IP load of water at these times completely inhibited water intake. Because of the contrasting effects of similar loads of water and isotonic saline on water intake of dehydrated rats, additional studies were carried out with an isosmotic solution of glucose (5%). IG administration (3% of body weight) of glucose inhibited water intake of dehydrated rats. IP administration (3% of body weight) attenuated the drinking response but did not reduce it to the level observed in dehydrated rats given an IP water load. When isosmotic glucose was administered at 0.5, 1.0, and 2.0 hr prior to allowing access to water, water intake was reduced significantly below that of dehydrated controls and to the same extent regardless of time of administration of the glucose load.(ABSTRACT TRUNCATED AT 250 WORDS)