Enhanced water intake after asymmetric hindbrain lesions

Previous reports indicate rats with lesions of the lateral parabrachial nucleus (IPBN) or lesions of the area postrema (AP) and adjacent nucleus of the solitary tract (NTS) consume abnormally large amounts of water after treatment with SC isoproterenol (ISOP) or angiotensin II. In the present study, we found that IPBN bilateral lesions resulted in increased water intake after ISOP treatment as noted previously. We also found that rats with ibotenic acid lesions of the left IPBN and a knife cut on the right side of the AP drank an abnormally large amount of water after treatment with ISOP. Interestingly, rats with lesions of the right IPBN and a knife cut on the left side of the AP did not show the enhanced drinking behavior. Rats with AP and adjacent NTS lesions had an increased sodium appetite, but water intake after ISOP treatment was not enhanced. Bilateral IPBN lesions and asymmetric lesions of the AP and IPBN did not result in enhanced sodium appetite. These data suggest that a pathway from the AP/mNTS to the 1PBN is important in the regulation of fluid balance.