| Abstract: | Bilateral medial preoptic lesions in rats dramatically lowered the rejection threshold for quinine-adulterated water but not for food in 24-hr forced-choice tests. The detection threshold for quinine in a two-bottle choice test, however, was unaffected by the medial preoptic lesion. Bilateral septal and lateral preoptic lesions had no effect on any quinine-adulteration tests. The enhanced rejection of quinine-adulterated water in a forced-choice test by medial-preoptic-damaged rats was also observed after 24-hr of water deprivation. Furthermore, the plasma osmolality of medial preoptic rats was significantly elevated above controls after 24-hr of water deprivation. These findings were interpreted as suggesting that a medial preoptic lesion produces a deficit in thirst-motivated behavior. |
