Osmoreceptor localization in the brain of the pigeon (Columba livia)

The area of the brain of pigeons that may be responsible for drinking following intravascular administration of osmotically effective solutes was investigated using infusions of water or isotonic and hypertonic solutions of NaCl or sucrose into various regions of the brains of conscious birds, and measuring the volume of water drunk. The preoptic area and the lateral hypothalamus were the only areas from which dose related drinking could be obtained in response to bilateral infusions of hypertonic NaCl or sucrose. Unilateral infusion of the hypertonic solutions rarely produced drinking. In contrast, water or isotonic NaCl, when infused unilaterally, in some cases caused some water intake. Drinking in response to intravenous infusion of hypertonic NaCl was not abolished by an 'apparent' lesion of the preoptic area. In several cases infusion of water or sucrose into the preoptic area caused a small volume of isotonic saline solution to be drunk. Thus the preoptic area and the lateral hypothalamus appear to be at least two of the areas involved in osmoregulation in the pigeon and may also be involved in sodium regulation.