We are aware of only three studies to date that have employed a modification of the DID model to deliver a compound directly to a specific brain nucleus in C57BL/6J mice. Infusions of the neuropeptide urocortin 1 (Ucn1) into the lateral septum altered the acquisition and expression of ethanol intake with the DID procedure (Ryabinin et al. 2008). The GABA-B receptor agonist baclofen reduced DID when infused into the anterior, but not the posterior, ventral tegmental area. Infusion did not affect drinking of either water or sugar water (Moore and Boehm 2009). More complex results were seen using the cannabinoid receptor agonist WIN 55-212,2. This compound increased DID drinking at the lowest dose, but suppressed it at two higher doses, but only if delivered to the posterior ventral tegmental area; all doses were ineffective in the anterior ventral tegmental area. These findings were complicated by effects on locomotor activity in some conditions, which may have competed with the consummatory drinking (Linsenbardt and Boehm 2009). In summary, the DID model has been used by several investigators, and a wide range of neural systems have been provisionally implicated by the pharmacological studies performed thus far.
