Functional mapping of the rat brain during drinking behavior: a fluorodeoxyglucose study.

Autoradiographic techniques using the radiolabeled glucose analog [14C]2-fluoro-2-deoxy-D-glucose (FDG) were used to map the functional activity in the CNS during drinking behavior. Rats were trained to drink water during a 1-h session each day. Half of the rats were injected with FDG and allowed to drink, while the other half were satiated prior to FDG injection. Uptake of FDG for drinking and control groups of rats was quantified in 60 brain structures from frontal cortex to cervical spinal cord. The largest percent increase in activity (96%) during drinking was in the lateral hypothalamus. Limbic structures with significant metabolic increases included the lateral septum (48%), lateral habenula (44%), and nucleus accumbens (32%). Thalamic nuclei activated included intralaminar (60%), zona incerta (51%), ventroposteromedial (50%), anterior ventral (47%), and dorsal medial (40%). Other structures with increases were the caudal caudate nucleus (53%) and the spinal trigeminal nucleus (45%). The findings were interpreted in light of related metabolic mapping studies of the effects of orofacial stimulation, dehydration, ingestion, arousal, and reward. It was concluded that this FDG study revealed primarily the involvement of structures linked to rewarding and arousal components of motivated drinking behavior, as well as sensorimotor correlates of the orofacial stimulation. The findings provide the first comprehensive functional map of brain systems related to drinking behavior in adult animals.