Mice lacking dopamine D1 receptors express normal lithium chloride-induced conditioned taste aversion for salt but not sucrose.

Conditioned taste aversion (CTA), is a form of Pavlovian learning wherein a novel flavour is powerfully associated with subsequent feelings of illness, and is afterwards avoided. In rats, pharmacological blockade of dopamine D1 receptors has been reported to prevent the expression of a CTA to the sweet taste of sucrose or saccharine. We used genetically modified mice to determine whether dopamine D1 receptors are necessary for the expression of a CTA. Food-deprived mice lacking the dopamine D1 receptor (D1r-/-) did not express a LiCl-induced (125 or 254 mg/kg) CTA to the sweet taste of 0.5 m sucrose, in agreement with previous pharmacological studies. However, water-deprived D1r-/- mice did express normal LiCl-induced (40, 150 and 254 mg/kg) CTA to a salty taste (0.2 m NaCl). Our results suggest that activation of D1 receptors might contribute to the strength of an aversive gustatory association, but might not be required for the formation of a CTA in general.