Drinking behavior and motor function in rat pups depleted of brain dopamine during development

The ability of rat pups depleted of brain dopamine (DA) at either 3 or 15 days of age to increase fluid intake in response to intracellular dehydration was studied. Despite near-total depletions of striatal DA, animals depleted at either age ingested normal amounts of fluid even as soon as 3-7 days after incurring the brain damage. The effects of DA receptor blockade on ingestion and motor function were also studied. Haloperidol had markedly different effects as a function of the age at which the depletions were sustained. Weanlings that were depleted of DA at 3 days of age failed to exhibit the drug-induced adipsia, akinesia, and catalepsy seen in controls and animals that were depleted at 15 days of age. These findings suggest that the DA depletions were performed at different periods of brain organization. The resultant neural controls of ingestion and motor function are qualitatively different in the two groups of depleted animals. Rats depleted at 3 days of age utilize nondopaminergic mechanisms, whereas animals lesioned at 15 days of age continue to rely upon residual DA neurons for both behaviors.