Comparison of the dipsogenic responsiveness of Long-Evans and Sprague-Dawley rats

Abstract

The dipsogenic responsiveness of the Sprague-Dawley (albino) and Long-Evans (hooded) strains of rats was compared. The responsiveness of the angiotensin II pathway for induction of drinking was assessed by means of acute administration of the beta-adrenoceptor agonist, isoproterenol (25 μg/kg, SC), angiotensin I (150 μg/kg, SC), and angiotensin II (150 μg/kg, SC). The results show that rats of the Long-Evans (hooded) strain drink less water than those of the Sprague-Dawley strain in response to acute administration of either isoproterenol or angiotensin I. However, there was no difference between groups in water intake resulting from administration of angiotensin II. This suggests that the Long-Evans strain has less capacity to convert angiotensin I to angiotensin II than the Sprague-Dawley strain, but that responsiveness of the Long-Evans strain to angiotensin II is similar to that of the Sprague-Dawley strain. The responsiveness of the osmoreceptor pathway for induction of drinking was also assessed both by measurement of the drinking response to acute administration of hypertonic saline (1% body weight of 1 M NaCl solution, IP) and a 24-hour dehydration. The results show that rats of the Long-Evans strain drink less water in response either to administration of hypertonic saline or to dehydration than those of the Sprague-Dawley strain. This suggests that responsiveness to stimulation of the osmoreceptor pathway of the Long-Evans strain induces less drinking than in the Sprague-Dawley. The results of these studies do not establish normalcy for either strain, but they do caution that significant differences in ingestive behaviors exist among the various strains, and suggest that, in the use of rats as models for humans in biomedical research, careful attention must be paid to the strain chosen.