Therefore, the specific contribution of frontal 5-HT2A receptors in the compulsive behavior of HD rats on SIP was also confirmed by the reduction of compulsive drinking after the microinfusion of the 5-HT2A/C agonist DOI into the medial prefrontal cortex; an effect that was reversed by its combination with the serotonin 5-HT2A receptor antagonist M100907 and not by the 5-HT2C antagonist SB242084. This evidence concerns the gene HTR2A and Huntington disease.