TPH2 and Anxiety: At the same time, we found that HFD intake affected serotonergic gene expression in the midbrain and pontine raphe nuclei, as evidenced by increased tph2, htr1a, and slc6a4 mRNA expression in subregions of the DR associated with anxiety-like defensive behavioral responses, particularly the cDRD or dorsomedial DR, a subregion that gives rise to serotonergic projections to forebrain anxiety circuits.