Operant drinking in pigs following intracerebroventricular injections of hypertonic solutions and angiotensin II.

The effect on operant drinking of intracerebroventricular injections of the following solutions has been investigated; hypertonic saline, hypertonic sugars, angiotensin II (Ang II) dissolved in water or dextrose, and Ang II dissolved in saline. Hypertonic (0.85 M) NaCl caused drinking in all pigs tested, but hypertonic (1.7 M) xylose, glucose or sucrose were less effective, indicating involvement of a cerebrospinal fluid sodium receptor mechanism as well as an osmoreceptor mechanism in the drinking responses. Angiotensin II in 0.15 M NaCl caused drinking in all pigs but when dissolved in water or dextrose it was ineffective. Injection of Ang II with hypertonic NaCl produced drinking similar in volume to the sum of the amount drunk in response to the individual stimuli. These results indicate that, in the pig, drinking in response to Ang II requires the presence of sodium ions.