Disordered drinking in developing spontaneously hypertensive rats.

Eating and drinking in spontaneously hypertensive (SHR) and Wistar-Kyoto (WKY) rats were measured at 5-17 wk of life. The SHR drank significantly more water in 24 h than WKY as early as wk 9, spilled more dry food than did WKY, and exhibited an inverse relation between 24-h water intake and dry food spilled. When eating a meal of dry food after 12 h food deprivation, SHR drank earlier and drank more in a 1-h test than WKY rats. Moreover, SHR exhibited (as early as wk 7) a striking pattern of interrupting eating to drink. This pattern was not present when SHR ate liquid food, and it was attenuated by infusion of water through a cheek fistula. Adult SHR (22 wk) salivated less than WKY in response to intraperitoneal 3.25 mg/kg pilocarpine nitrate. When developing SHR and WKY were maintained on liquid and solid food, SHR gained disproportionately more weight than WKY during development. When young SHR were permitted to drink no more water than WKY rats, the development of hypertension was retarded, and body weight gain was slowed. Because restricted access to food, which produced an equivalent slowing of body weight gain as did restricted access to water, also retarded development of hypertension, it appears that restricted access to water retards development of hypertension due to delayed growth. These results demonstrate that hyperdipsia, apparently caused by deficient salivary function, is not necessary for the development of hypertension in SHR.