Regulatory drinking: Do the physiological substrates have an ecological niche?

The current physiological theories of thirst are briefly reviewed, and a number of experiments in which drinking behavior does not conform to such models are described. These include parenteral self-administration and taste adulteration experiments. Regulatory drinking may be identified in these preparations, but is substantially different from that defined by simple physiological models. Similarly aberrant regulatory drinking is seen after a variety of hypothalamic lesions, and the interpretation of such experiments is discussed. Finally, the relevance of some laboratory paradigms to the normal (ethologically determined) controls of drinking is questioned, and it is suggested such factors should be incorporated into future models.