Water intake after stomach loads of NaCl in 30-, 40-, and 50-day-old Mongolian gerbils.

Ninety Mongolian gerbils (Meriones unguiculatus), 15 male and 15 female in each of three age groups (30-, 40-, and 50-day-old), were stomach loaded with either water, 6% NaCl, or 12% NaCl (wt./vol.). No differences were observed in fluid intake or in body weight 24 hours after the load. These data were totally unlike the findings in rats. The lack of intergroup differences were probably attributable to the gerbil's unusual adrenal and kidney structure and hormonal controls.

Effects of polyethylene glycol on water or saline intake in 30- and 50-day-old Mongolian gerbils.

Sixty 30-day-old male and female gerbils and sixty 50-day-old male and female gerbils were injected subcutaneously with either a .9% NaCl vehicle, 10% polyethylene glycol (P.G.), or 30% P.G. and given access to either water or .9% NaCl to drink. The .9% NaCl vehicle and the 10% P.G. injections were ineffective in increasing fluid intake. The Ss in the 30% P.G. injection level showed an increase in intake when saline was offered but did not increase their intake when water was the only solution available. The results are discussed in terms of compensatory mechanisms which subserve osmoregulation.

Effects of polyethylene glycol on water and saline intake in the Mongolian gerbil.

To establish the water balance regulatory ability of gerbils in response to a hypovolemic dipsogen, adult female gerbils (50-70 g) were injected subcutaneously with either a .9% NaCl vehicle or 10% or 30% (wt/vol) polyethylene glycol (mol wt 20,000). At each injection level one-half of the Ss had access to water, the other to .9% NaCl after injection. There was a significant increase in fluid intake associated with injection doses and Ss drank significantly more when allowed saline to drink rather than water. In Experiment II under a similar set of manipulations, hematocrit values were obtained at 12 and 24 hours after injection and showed decreasing blood volume levels which apparently served as the thirst stimulus. The results were discussed in terms of the voluntary dehydration findings of Stricker on rats and thus demonstrated the similarity of gerbils and rats in response to extracellular insult.

Conditioned thirst in rats.

The purpose of these studies was to assess the appropriateness of control groups in previous thirst conditining studies and to demonstrate that conditioned drinking can be viewed as a classically conditioned appetitive response. In Experiment I (N = 48) thirst was conditioned by the procedure employed by Solomon and Swanson [see Mowrer (11)]. With the use of a "novel cage" group, suppression rather than enhancement of intake was obtained. These and other investigators' results were interpreted in the light of the appropriateness of control groups. In Experiment II (N = 30) rate demonstrated increased water intake at zero hours water deprivation in the presence of an external stimulus previously paired with an increasing motive state. Intakes monitored at half-hour intervals revealed that "low-to-high" drive associated stimuli did not affect overall intake but did induce differentiation in drinking patterns causing first enhancement and then reduction in intake amounts. The results were agreement with Seligman et al. (14) who suggested that elicitation of the prepared mechanism evokes drinking, but water regulation controls do not allow prolonged hyperdipsia.

Water intake after stomach loads of NaCl in Mongolian gerbils.

Sixty mongolian gerbils (Meriones unguiculatus), 30 male and 30 female, were stomach loaded (2% b.w.) with either water or .9, 2, 6, 10, or 12% NaCl (wt x vol.). Unlike male rats, male gerbils did not lose weight. Female gerbils, like female rats, did not lose weight. However, female gerbils did not increase their water intake at any concentration, whereas males increased their water intake only at the 10 and 12% levels. These data are very much unlike those for the rat (male and female) which show an increase in water intake in response to NaCl solutions above isotonicity.

The effects of stomach loads of hypertonic NaCl on thyroidectomized prepubescent rats.

Prepubescent male and female rats (N = 56) were surgically thyroidectomized and given stomach loads of .9% or 6.0% NaCl. The 6.0% NaCl, thyroidectomized S s responded by decreasing food intake and losing weight 24 hours after loading. Normal S s did not, and no sex difference was found. The .9% NaCl thyroidectomized S s drank significantly less than the normals. The results were interpreted in terms of thyroid hormone activity which affects renal function.

Establishment of a secondary drive based on thirst: a replication.

In order to establish a secondary drive based on thirst, 16 male albino rats were deprived of water for 23 hours per day for 14 days in square cages. At the end of each 23-hour period, the Ss were placed in triangular cages with free access to water for 1/2 hour followed by 1/2 hour in a circular cage with no water available. On day 15 the Ss were divided into two groups following satiation in the triangular cage. The control Ss were placed in the circular cages with water present for the first time, and experimental Ss were placed in the square cages with water present for the first time. During this 1/2-hour period the experimental Ss drank significantly more than the control Ss which indicated the presence of thirst fear in the experimental group.